AIX 5L 性能和系统调优

Front cover
IBM
Certification Study Guide AIX 5L Performance and
System Tuning
Developed specifically for the purpose
of preparing for AIX certification
Makes an excellent companion
to classroom education
For experienced AIX
professionals
Tim Dasgupta
Stephen Sommer
ibm.com/redbooks
International Technical Support Organization
IBM ^ Certification Study Guide AIX 5L Performance and System Tuning
December 2002
SG24-6184-01
Note: Before using this information and the product it supports, read the information in
“Notices” on page xiii.
Second Edition (December 2002)
This edition applies to AIX 5L Version 5.1 (5765-E61) and subsequent releases running on an
IBM ^ pSeries or RS/6000 server.
© Copyright International Business Machines Corporation 2000, 2002. All rights reserved.
Note to U.S. Government Users Restricted Rights -- Use, duplication or disclosure restricted by GSA ADP Schedule
Contract with IBM Corp.
Contents
Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
The team that wrote this redbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
Become a published author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Comments welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
Chapter 1. Certification overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Certification requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 Required prerequisite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Recommended prerequisite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.3 Information and registration for the certification exam . . . . . . . . . . . . 2
1.1.4 Core requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Certification education courses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Chapter 2. Performance tuning: Getting started . . . . . . . . . . . . . . . . . . . . . 7
2.1 Introduction to concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 CPU performance overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 The sar command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 The time command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3.1 The vmstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3.2 The ps command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.3 The tprof command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.4 The nice and renice commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.5 The schedtune command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4 Memory performance overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4.1 The vmstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.4.2 The ps command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4.3 The lsps command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4.4 The svmon command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4.5 The vmtune command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4.6 The rmss command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.5 Disk I/O performance overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.5.1 The iostat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
© Copyright IBM Corp. 2002. All rights reserved.
iii
2.5.2 The filemon command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.3 The fileplace command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.5.4 The lslv command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.6 Network performance overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.6.1 The netstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.6.2 The nfsstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.6.3 The netpmon command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.7 The performance diagnostic tool (PDT) . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.7.1 Installing and enabling PDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.8 Service level agreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.10 Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.10.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Chapter 3. CPU and memory performance monitoring tools . . . . . . . . . . 39
3.1 The sar command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.1.1 Accounting software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.1.2 Examples of using the sar command . . . . . . . . . . . . . . . . . . . . . . . . 40
3.1.3 The sar command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.1.4 The sadc command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.1.5 The sa1 and sa2 commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2 The vmstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3 The ps command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.3.1 Use of the ps command in a CPU usage study . . . . . . . . . . . . . . . . 62
3.3.2 Use of the ps command in a memory usage study . . . . . . . . . . . . . . 65
3.4 The tprof command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4.1 Using the tprof general report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4.2 Using tprof on a program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.5 The svmon command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.5.1 The svmon global report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.5.2 The svmon user report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.5.3 The svmon process report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.5.4 The svmon segment report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.5.5 The svmon detailed segment report . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.5.6 The svmon command report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
3.5.7 The svmon Workload Manager (WLM) class report . . . . . . . . . . . . . 88
3.5.8 The svmon command flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.6 The rmss command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.7 The topas command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.7.1 Common uses of the topas command . . . . . . . . . . . . . . . . . . . . . . . 96
3.8 The emstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.9 The /proc file system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
3.10 General performance guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
3.11 Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.11.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
3.12 Exercises. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Chapter 4. Disk I/O performance monitoring tools . . . . . . . . . . . . . . . . . 117
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
4.2 The iostat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
4.2.1 Historical disk I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
4.2.2 Using disk I/O pacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
4.2.3 TTY and CPU utilization report . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
4.2.4 The iostat command on SMP systems . . . . . . . . . . . . . . . . . . . . . . 126
4.2.5 Disk utilization report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
4.3 The lockstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
4.4 LVM performance analysis using the lslv command . . . . . . . . . . . . . . . . 131
4.4.1 Logical volume attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
4.4.2 Logical volume fragmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
4.4.3 Logical volume allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
4.4.4 Highest LVM performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.5 LVM and file system monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.5.1 The filemon command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.5.2 Report analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
4.5.3 Typical AIX system behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.6 File system performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
4.6.1 AIX file system organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
4.6.2 Enhanced journaled file system (JFS2) . . . . . . . . . . . . . . . . . . . . . 152
4.6.3 Journeled file system (JFS) log management . . . . . . . . . . . . . . . . . 156
4.6.4 The fileplace command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
4.6.5 File system defragmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
4.7 General recommendations for I/O performance . . . . . . . . . . . . . . . . . . . 160
4.7.1 Logical volume organization for highest performance. . . . . . . . . . . 160
4.7.2 Logical volume striping recommendations . . . . . . . . . . . . . . . . . . . 161
4.7.3 RAID recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
4.7.4 File system related performance issues . . . . . . . . . . . . . . . . . . . . . 162
4.7.5 Paging space related disk performance issues. . . . . . . . . . . . . . . . 163
4.8 Overhead of using performance tools . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
4.9 Command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
4.9.1 The filemon command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
4.9.2 The fileplace command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
4.9.3 The lslv command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
4.10 Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
4.10.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
4.11 Exercises. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
Contents
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Chapter 5. Network performance tools . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
5.2 Adapter transmit and receive queue tuning. . . . . . . . . . . . . . . . . . . . . . . 174
5.3 Protocols tuning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
5.4 Network performance monitoring tools . . . . . . . . . . . . . . . . . . . . . . . . . . 179
5.4.1 The vmstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
5.4.2 The traceroute command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
5.4.3 The netstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
5.4.4 The entstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
5.4.5 The fddistat command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
5.4.6 The tokstat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
5.4.7 The atmstat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
5.4.8 The netpmon command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
5.4.9 The tcpdump and iptrace commands . . . . . . . . . . . . . . . . . . . . . . . 190
5.5 Network performance management tools . . . . . . . . . . . . . . . . . . . . . . . . 192
5.6 Name resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
5.7 NFS performance tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
5.7.1 NFS server-side performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
5.7.2 NFS client-side performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
5.7.3 Mount options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
5.8 Command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
5.8.1 The netstat command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
5.8.2 The tcpdump command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
5.8.3 The iptrace command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
5.8.4 The ipreport command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
5.9 Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
5.9.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
5.10 Exercises. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Chapter 6. Performance management tools . . . . . . . . . . . . . . . . . . . . . . . 205
6.1 The AIX scheduler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
6.1.1 Priority calculation on AIX versions prior to 4.3.2 . . . . . . . . . . . . . . 207
6.1.2 Priority calculation on AIX Version 4.3.2 and later . . . . . . . . . . . . . 210
6.2 Multiple run queues with load balancing . . . . . . . . . . . . . . . . . . . . . . . . . 211
6.2.1 Initial load balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
6.2.2 Idle load balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
6.2.3 Frequent periodic load balancing . . . . . . . . . . . . . . . . . . . . . . . . . . 213
6.2.4 Infrequent periodic load balancing . . . . . . . . . . . . . . . . . . . . . . . . . 214
6.3 Scheduler performance management . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
6.3.1 The schedtune command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
6.3.2 The nice and renice commands . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
6.4 The bindprocessor command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
6.5 The vmtune command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
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6.6 Workload Manager (WLM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
6.6.1 WLM concepts and architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
6.6.2 Automatic assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
6.6.3 Manual assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
6.6.4 Backward compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
6.6.5 Resource sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
6.6.6 Rset registry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
6.7 Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
6.7.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
6.8 Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Chapter 7. Performance scenario walkthroughs . . . . . . . . . . . . . . . . . . . 249
7.1 CPU performance scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
7.1.1 Data collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
7.1.2 Data analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
7.1.3 Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
7.2 I/O performance scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
7.2.1 Data collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
7.2.2 Data analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
7.2.3 Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
7.3 Additional I/O scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
7.3.1 CPU and kernel thread I/O wait bottleneck scenario . . . . . . . . . . . 256
7.3.2 I/O distribution bottleneck scenario . . . . . . . . . . . . . . . . . . . . . . . . . 257
7.3.3 Logical volume fragmentation scenario. . . . . . . . . . . . . . . . . . . . . . 259
7.3.4 Monitoring scenario using filemon. . . . . . . . . . . . . . . . . . . . . . . . . . 260
7.3.5 Logical volume allocation scenario . . . . . . . . . . . . . . . . . . . . . . . . . 260
7.4 Paging performance scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
7.4.1 Data collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
7.4.2 Data analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
7.4.3 Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
Chapter 8. Scenario assessment quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
8.1 Scenario one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
8.1.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
8.2 Scenario two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
8.2.1 Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
Appendix A. The error log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
Managing the error log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
Configuring error log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
Clearing the error log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
Reading error logs in details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
The errpt command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
Contents
vii
Formatted output from errpt command . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
The errpt command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Appendix B. Installing the performance tools . . . . . . . . . . . . . . . . . . . . . 299
Tools and filesets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Tools by resource matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
Performance Toolbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
The installp command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
The lslpp command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
The lppchk command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Abbreviations and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
Related publications . . . . . . . . . . . . . . . . . . . . . .
IBM Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other resources . . . . . . . . . . . . . . . . . . . . . . . .
Referenced Web sites . . . . . . . . . . . . . . . . . . . . . .
How to get IBM Redbooks . . . . . . . . . . . . . . . . . . .
IBM Redbooks collections . . . . . . . . . . . . . . . . .
......
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329
329
330
330
331
331
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
viii
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figures
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
3-1
4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
5-1
6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
6-9
6-10
6-11
6-12
6-13
8-1
8-2
8-3
8-4
8-5
A-1
General performance tuning flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Process state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
VMM segments from a client perspective . . . . . . . . . . . . . . . . . . . . . . . 16
VMM segments from a process perspective . . . . . . . . . . . . . . . . . . . . . 17
VMM memory registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Logical volume device driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Dependencies in a volume group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Network parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Performance tuning flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
The topas command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Disk, LVM, and file system levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
SMIT screen for changing characteristics of operating system . . . . . . 121
The smitty chgsys fastpath to set high and low water marks . . . . . . . . 122
The smitty chgsys fastpath to set automatic reboot . . . . . . . . . . . . . . . 124
LVM intra-disk positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Striping a logical volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
JFS organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
The smitty mklv add a logical volume dialog . . . . . . . . . . . . . . . . . . . . 157
UDP/TCP/IP data flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Run queue prior to AIX Version 4.3.3 . . . . . . . . . . . . . . . . . . . . . . . . . 208
AIX Version 4, 128 run queues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Run queue on AIX Version 4.3.3 and later . . . . . . . . . . . . . . . . . . . . . 212
CPU penalty example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
Web-based System Manager Overview and Tasks dialog . . . . . . . . . 229
Hierarchy of classes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
Resources cascading through tiers . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
SMIT with the class creation attributes screen . . . . . . . . . . . . . . . . . . 234
SMIT panel shows the additional localshm attribute . . . . . . . . . . . . . . 236
Resource set definition for a specific class . . . . . . . . . . . . . . . . . . . . . 243
SMIT main panel for resource set management . . . . . . . . . . . . . . . . . 244
SMIT panel for rset registry management . . . . . . . . . . . . . . . . . . . . . . 245
SMIT panel to add a new resource set . . . . . . . . . . . . . . . . . . . . . . . . 246
The ps command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
The vmstat command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
The iostat command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
The netstat command output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
The vmstat and iostat command outputs . . . . . . . . . . . . . . . . . . . . . . . 282
smitty errpt output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
© Copyright IBM Corp. 2002. All rights reserved.
ix
B-1
B-2
B-3
x
smitty list_software output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
smitty install_all . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
Commit software updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Tables
2-1
2-2
2-3
2-4
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
4-1
4-2
4-3
4-4
4-5
4-6
4-7
5-1
5-2
5-3
5-4
5-5
6-1
6-2
6-3
6-4
6-5
6-6
A-1
B-1
B-2
B-3
B-4
B-5
B-6
Hardware resources and logical resources . . . . . . . . . . . . . . . . . . . . . . . 8
Processes and threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
VMM-related output from the vmstat command . . . . . . . . . . . . . . . . . . . 21
The performance diagnostic tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Commonly used flags of the sar command . . . . . . . . . . . . . . . . . . . . . . 45
CPU-related ps output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Commonly used flags of the ps command. . . . . . . . . . . . . . . . . . . . . . . 64
Memory-related ps output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Commonly used flags of the svmon command . . . . . . . . . . . . . . . . . . . 90
Commonly used flags of the rmss command . . . . . . . . . . . . . . . . . . . . . 93
Commonly used flags of the topas command . . . . . . . . . . . . . . . . . . . . 95
Function of pseudo files in /proc/<pid> directory . . . . . . . . . . . . . . . . . 105
General performance guidlines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Commonly used flags of the iostat command . . . . . . . . . . . . . . . . . . . 119
I/O pacing parameters effect on the cp and vi commands. . . . . . . . . . 122
Commonly used flags of the lockstat command . . . . . . . . . . . . . . . . . 129
RAID levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Commonly used flags of the filemon command . . . . . . . . . . . . . . . . . . 164
Commonly used flags of the fileplace command . . . . . . . . . . . . . . . . . 164
Commonly used flags of the lslv command . . . . . . . . . . . . . . . . . . . . . 165
Default search order for the nslookup command . . . . . . . . . . . . . . . . . 194
Commonly used flags of the netstat command . . . . . . . . . . . . . . . . . . 199
Commonly used flags of the tcpdump command . . . . . . . . . . . . . . . . . 200
Commonly used flags of the iptrace command . . . . . . . . . . . . . . . . . . 200
Commonly used flags of the ipreport command . . . . . . . . . . . . . . . . . 201
Commonly used flags of the schedtune command . . . . . . . . . . . . . . . 218
Commonly used flags of the nice command . . . . . . . . . . . . . . . . . . . . 220
Commonly used flags of the renice command . . . . . . . . . . . . . . . . . . . 221
Commonly used flags of the vmtune command . . . . . . . . . . . . . . . . . 224
List of process types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Examples of class assignment rules . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Commonly used flags of the errpt command . . . . . . . . . . . . . . . . . . . . 295
Commands or tools, path names, and filesets . . . . . . . . . . . . . . . . . . . 300
Performance tools by resource matrix . . . . . . . . . . . . . . . . . . . . . . . . . 303
Performance Toolbox releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
General installp summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Commonly used flags of the lslpp command . . . . . . . . . . . . . . . . . . . . 314
Commonly used flags of the lppchk command . . . . . . . . . . . . . . . . . . 315
© Copyright IBM Corp. 2002. All rights reserved.
xi
xii
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Notices
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IBM may not offer the products, services, or features discussed in this document in other countries. Consult
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COPYRIGHT LICENSE:
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© Copyright IBM Corp. 2002. All rights reserved.
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xiv
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Preface
The AIX and IBM ^ pSeries Certifications offered through the
Professional Certification Program from IBM are designed to validate the skills
required of technical professionals who work in the powerful and often complex
environments of AIX and IBM ^ pSeries. A complete set of
professional certifications is available. It includes:













IBM Certified AIX User
IBM Certified Specialist - Business Intelligence for RS/6000
IBM Certified Specialist - Domino for RS/6000
IBM ^ Certified Specialist - p690 Solutions Sales
IBM ^ Certified Specialist - p690 Technical Support
IBM ^ Certified Specialist - pSeries Sales
IBM ^ Certified Specialist - pSeries AIX System
Administration
IBM ^ Certified Specialist - pSeries AIX System Support
IBM ^ Certified Specialist - pSeries Solution Sales
IBM Certified Specialist - RS/6000 SP and PSSP V3
IBM Certified Specialist - Web Server for RS/6000
IBM ^ Certified Specialist - pSeries HACMP for AIX
IBM ^ Certified Advanced Technical Expert - pSeries and
AIX 5L
Each certification is developed by following a thorough and rigorous process to
ensure the exam is applicable to the job role and is a meaningful and appropriate
assessment of skill. Subject matter experts who successfully perform the job
participate throughout the entire development process. They bring a wealth of
experience into the development process, making the exams much more
meaningful than the typical test that only captures classroom knowledge and
ensuring the exams are relevant to the real world. Thanks to their effort, the test
content is both useful and valid. The result of this certification is the value of
appropriate measurements of the skills required to perform the job role.
This IBM Redbook is designed as a study guide for professionals wishing to
prepare for the AIX 5L Performance and System Tuning certification exam as a
selected course of study in order to achieve the IBM ^ Certified
Advanced Technical Expert - pSeries and AIX 5L certification.
This IBM Redbook is designed to provide a combination of theory and practical
experience needed for a general understanding of the subject matter. It also
provides sample questions that will help in the evaluation of personal progress
© Copyright IBM Corp. 2002. All rights reserved.
xv
and provide familiarity with the types of questions that will be encountered on the
exam.
This publication does not replace practical experience, nor is it designed to be a
stand-alone guide for any subject. Instead, it is an effective tool that, when
combined with education activities and experience, can be a very useful
preparation guide for the exam.
For additional information about certification and instructions on how to register
for an exam, visit our Web site at:
http://www.ibm.com/certify
The team that wrote this redbook
This redbook was produced by a team of specialists from around the world
working at the International Technical Support Organization, Austin Center.
Tim Dasgupta is an IBM Certified AIX Advanced Technical Expert (CATE). He
works as a Senior Systems Architect at IBM Global Services in Canada. He has
over eight years of experience in the areas of AIX, RS/6000, and pSeries. He is
currently the Team Leader of Midrange Architecture Group in Montreal, Canada.
Stephen Sommer is an IBM Certified AIX Advanced Technical Expert (CATE),
AIX Version 4.3.3 and 5.1. He works as a Senior IT Specialist at Faritec
Services, an IBM Business Partner in Johannesburg, South Africa. He has eight
years of experience in Midrange Support for AIX, RS/6000, and pSeries, both in
South Africa and the United Kingdom.
The authors of the first edition are:
Thomas Herlin
IBM Denmark
André de Klerk
IBM South Africa
Thomas C. Cederlöf IBM Sweden
Tomasz Ostaszewski Prokom Software SA in Poland
The project that produced this publication was managed by:
Scott Vetter
IBM Austin
Special thanks to:
Shannan L DeBrule IBM Atlanta
Darin Hartman
xvi
Program Manager, AIX Certification
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Thanks to the following people for their invaluable contributions to this project:
Jesse Alcantar, Greg Althaus, Larry Brenner, Shawn Mullen, Brian
Nicholls, Greg Flaig
IBM Austin
Michelle Page-Rivera
IBM Atlanta
John Hance and Tony Steel
IBM Australia
Edward Geraghty
IBM Boston
Adnan Ikram
IBM Pakistan
Christopher Snell
IBM Raleigh
Stephen Atkins and Peter Mayes
IBM U.K.
Karl Borman
ILS Austin
Malin Cederberg and Robert Olsson
ILS Sweden
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Preface
xvii
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xviii
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
1
Chapter 1.
Certification overview
This chapter provides an overview of the skill requirements needed to obtain an
IBM Advanced Technical Expert certification. The following chapters are
designed to provide a comprehensive review of specific topics that are essential
for obtaining the certification IBM ^ Certified Advanced
Technical Expert - pSeries and AIX 5L.
This level certifies an advanced level of AIX knowledge and understanding, both
in breadth and depth. It verifies the ability to perform in-depth analysis, apply
complex AIX concepts, and provide resolution to critical problems, all in a variety
of areas within AIX.
© Copyright IBM Corp. 2002. All rights reserved.
1
1.1 Certification requirements
To attain the IBM ^ Certified Advanced Technical Expert pSeries AIX 5L certification, you must pass four tests.
One test is the prerequisite in either pSeries AIX System Administration or
pSeries AIX System Support. The other three tests are selected from a variety of
pSeries and AIX topics. These requirements are explained in greater detail in the
sections that follow.
1.1.1 Required prerequisite
Prior to attaining the IBM ^ Certified Advanced Technical
Expert - pSeries and AIX 5L certification, you must be certified as either an:
 IBM ^ Certified Specialist - pSeries AIX System
Administration
or
 IBM ^ Certified Specialist - pSeries AIX System Support
1.1.2 Recommended prerequisite
A minimum of six to 12 months experience in performing in-depth analysis and
applying complex AIX concepts in a variety of areas within AIX is a
recommended prerequisite.
1.1.3 Information and registration for the certification exam
For the latest certification information, see the following Web site:
http://www.ibm.com/certify
1.1.4 Core requirements
Select three of the following exams. You will receive a Certificate of Proficiency
for tests when passed.
AIX 5L Installation and System Recovery
Test 233 was developed for this certification.
Preparation for this exam is the topic of IBM ^ Certification
Study Guide - AIX Installation and System Recovery, SG24-6183.
2
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
AIX 5L Performance and System Tuning
The following objectives were used as a basis when the certification test 234 was
developed. Some of these topics have been regrouped to provide better
organization when discussed in this publication.
Preparation for this exam is the topic of this publication.
Section I - Measurements and baseline
Section I cover measurements and baseline.
1. Determine successful operating levels for stable/comparable system.
a. Run the oslevel command to determine current OS version.
b. Run the lslpp command to list installed software.
c. Run errpt to determine if there are any unresolved hardware problems.
2. Take snapshot/baseline of system.
a. Install perfagent.tools fileset.
b. Install bos.perf fileset.
c. Install bos.adt.samples fileset.
d. Verify that you have the latest filesets for all of the above steps; if not,
obtain the latest and install them.
e. Identify time to take performance measurements.
f. Run perfpmr to gather operating statistics.
g. Run no, nfso, vmtune, or schedtune to gather tuning parameters if
appropriate.
h. Run wlm (Workload Manager) to gather tuning parameters.
i. Run topas (Performance Monitoring Tool) to gather tuning parameters.
3. Establish performance policies for the new system (system to be tuned).
a. Determine which measurements are relevant.
b. Define (using Service Level Agreements) what a well-behaved system is.
Section II - Performance monitoring and analysis
Section II covers performance monitoring and analysis.
1. Determine if CPU bound.
a. Run vmstat, iostat, sar, or topas to gather CPU utilization information.
b. Add %user and %sys to determine if CPU bound.
2. If CPU bound, run additional tools like tprof and ps to determine which
process is causing the bottleneck. Determine if memory bound.
Chapter 1. Certification overview
3
a. Run vmstat to gather memory utilization information.
b. Look at pi and po output columns to determine if memory bound.
c. Use /proc to determine if the system is memory bound.
d. If memory bound, run tools like svmon and ps to determine which process
is causing the bottleneck.
3. Determine if I/O bound.
a. Run iostat or topas to gather disk I/O utilization information.
b. Look at %iowait and %tm_act to determine if I/O bound.
c. If I/O bound, run tools like filemon, fileplace, and lslv to determine
which process, disk, or adapter is causing the bottleneck.
4. Determine if network bound.
a. Run netpmon, netstat, or nfsstat to gather network utilization information.
b. Run entstat or fddistat to gather adapter-specific information.
c. Look at output to determine if network bound.
d. If network bound, run tools like no, netpmon, nfso, or lsattr to assist in
determining the cause of the bottleneck.
Section III - Tuning
Section III covers tuning.
1. Tune application.
Analyze application with profiling tools like tprof, gprof, and prof to identify
potential code optimization opportunities.
2. Tune CPU.
a. Balance system workload.
b. Tune scheduler using nice/renice to give different priorities to running
processes (prevent CPU hogging).
c. Tune scheduler algorithm using schedtune to fine tune priority formulas,
setting timeslices.
3. Tune memory.
a. Add more real memory to increase available memory.
b. Tune virtual memory manager using vmtune command.
c. Tune memory overcommitment algorithm using schedtune command to
prevent thrashing.
4. Tune I/O.
4
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
a. Place data on physical disks appropriately (striping) using tools such as
reorgvg, migratepv, or chlv.
b. Use vmtune to modify file system, lvm, and paging parameters.
c. Use chgsys to tune high/low water marks for pending write I/Os (I/O
pacing).
d. Place JFS logs on different physical disks from file system data.
e. Defragment files; make them contiguous.
5. Tune network.
a. Tune transmit and receive queues using chdev.
b. Use no to tune TCP/IP options.
c. Use ifconfig or no to adjust MTU size appropriate for your network
topology.
d. Use /etc/netsvc.conf or NSORDER environment variable to override
default order for name resolution.
e. Tune NFS options (if appropriate).
Section IV - System sizing
Section IV covers system sizing.
1. Gather additional information.
a. Run performance monitoring tools to gather additional information.
b. Analyze data to predict future system requirements.
2. Use sizing tools.
Analyze results of sizing tool.
AIX 5L Problem Determination Tools and Techniques
Test 235 was developed for this certification.
Preparation for this exam is the topic of IBM ^ Certification
Study Guide - AIX Problem Determination Tools and Techniques, SG24-6185.
AIX 5L Communications
Test 236 was developed for this certification.
Preparation for this exam is the topic of IBM ^ Certification
Study Guide - AIX Communications, SG24-6186.
pSeries HACMP for AIX
Test 187 was developed for this certification.
Chapter 1. Certification overview
5
Preparation for this exam is the topic of IBM ^ Certification
Study Guide - pSeries HACMP for AIX, SG24-6187.
RS/6000 SP and PSSP V3.1
Test 188 was developed for this certification.
Preparation for this exam is the topic of IBM ^ Certification
Study Guide - RS/6000 SP, SG24-5348.
p690 Technical Support
Test 195 was developed for this certification.
An IBM Redbook is planned for first quarter 2003 on this subject.
1.2 Certification education courses
Courses are offered to help you prepare for the certification tests. For a current
list, visit the following Web site, locate your test number, and select the education
resources available:
http://www.ibm.com/certify/tests/info.shtml
6
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
2
Chapter 2.
Performance tuning: Getting
started
In this chapter, the following topics are covered:
 Introduction to concepts and tools
 Performance tuning flowchart
In general, the performance tuning issues can be divided into two areas:
 System management
 Application development
The application developer will usually view performance more from a user’s
perspective than a system perspective; for example, the user response time and
system interactions are the concerns addressed during the design phase, not the
overall system performance. This aspect of performance tuning, optimization of
code, is outside the scope of this publication. This publication focuses on the
system management aspects.
Many of the commands introduced in this chapter are discussed in detail
throughout this publication (as referenced).
© Copyright IBM Corp. 2002. All rights reserved.
7
2.1 Introduction to concepts
Performance management, from a system management point of view, is usually
concentrated on the allocation of existing resources, but also includes allocation
of additional resources and establishment of system policies. Therefore,
performance tuning can be defined as the application and allocation of resources
to best meet the defined requirements and goals.
From this definition of performance tuning, the following list provides a set of
tasks that are part of performance tuning:
1. Identify the workload.
If the system to tune is a workstation, then the most probable goal is fast
response time.
If the system is a multiuser environment, the goal is to maximize throughput
within a given response time or minimize response time under a consistent
workload.
If the system is a server, maximizing throughput for a given response time is
usually the goal.
2. Define and prioritizing goals.
Before starting a tuning exercise, you need to have clear goals in mind. In
other words, how will you know when you have finished tuning the system?
Bear in mind that response time and throughput are not the same thing and
that you need to focus on one or the other for each application. It is also
important to realize that tuning is a process of compromise—that you will
likely be taking resources away from one application to give to another. A
clear understanding of the relative priorities that operate in your environment
is also an essential prerequisite to tuning your system.
3. Identify the required resources.
Performance of a given workload is determined by the availability and speed
of certain critical resources. Resources can be divided into two areas:
Physical resources and logical resources. Table 2-1 provides examples of
hardware resources with their logical resources.
From the points discussed, steps 1 through 3 are part of planning and
researching.
Table 2-1 Hardware resources and logical resources
8
Hardware resource
Logical resource
CPU
Process time slice
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Hardware resource
Logical resource
Memory
Page frame
Stacks
Buffers
Queues
Tables
Disk space
Logical volumes
File systems
Files
Communication lines
Packets
Channels
4. Minimize resource requirements.
Resource requirements can be minimized by using optimized code,
organizing data efficiently, rescheduling low-prioritized jobs, making the right
choice when to use remote resources, and so on. This is the stage where the
actual hands-on tuning will occur.
5. Control allocation of resources.
Resources to control include disk space and process priority control. Disk
space for users, or groups of users, can easily be managed with a quota, and
process priority can be handled with the Workload Manager or by
manipulating the scheduler.
6. Repeat steps 3 to 5 as necessary.
7. Add additional resources as required.
In the following section, a common performance tuning flowchart will be briefly
discussed.
2.2 CPU performance overview
When investigating a performance problem, CPU constraint is probably the
easiest to find. That is why most performance analysts start by checking for CPU
constraints, and then work their way through the flowchart shown in Figure 2-1
on page 10.
Chapter 2. Performance tuning: Getting started
9
Figure 2-1 General performance tuning flowchart
If a system is CPU bound, investigation should focus on the two entities using the
CPU: Processes and threads. The CPU’s basic work unit is the thread, so a
process must have at least one thread. Commonly (on AIX Version 4), a process
is multi-threaded, which means that a process can use multiple threads to
accomplish its task. In Figure 2-2 on page 11, the relationship between
processes and threads is symbolized.
When initiating a process, the first resource to be allocated is a slot in the
process table; before this slot is assigned, the process is in SNONE state. While
the process is undergoing creation (waiting for resources [memory] to be
allocated) it is in SIDL state. These two states are together called the I state.
10
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure 2-2 Process state
When a process is in the A state, one or more of its threads are in the R state.
This means they are ready to run. A thread in this state has to compete for the
CPU with all other threads in the R state. Only one process can use the CPU at
any given time.
If a thread is waiting for an event or for the I/O, the thread is said to be sleeping,
or in the S state. When the I/O is complete, the thread is awakened and placed in
the ready-to-run queue.
If a thread is stopped with the SIGSTOP signal (to be awakened with the
SIGCONT signal), it is in the T state while suspended.
Manipulating the run queue, the process and thread dispatcher, and priority
calculation are all ways to tune (and misstune, if not carefully done) the CPU. The
run queue and how to decide which thread is to be prioritized is discussed in
Chapter 6, “Performance management tools” on page 205.
When tuning the CPU, you need to know what can be tuned on a process level
and what can be tuned on a thread level and choose accordingly. Table 2-2 on
Chapter 2. Performance tuning: Getting started
11
page 12 provides a list that associates several process-related properties with
thread-related properties.
Table 2-2 Processes and threads
Process properties
Thread properties
PID and PGID
TID
UID and GID
Stack
Environment
Scheduling policy
Cwd
Pending signals
File descriptors
Blocked signals
When working in the area of CPU performance tuning, you should use historical
performance information for comparison reasons. Usually, performance has
subjective view points. To avoid confusion, hard copies of performance statistics,
from a time when users did not report poor system performance, should be filed.
A very useful tool for this task is the sar command.
2.2.1 The sar command
Two shell scripts, /usr/lib/sa/sa1 and /usr/lib/sa/sa2, are structured to be run by
the cron command and provide daily statistics and reports. Sample stanzas are
included (but commented out) in the /var/spool/cron/crontabs/adm crontab file to
specify when the cron daemon should run the shell scripts. The sa1 script
creates one output file each day and the sa2 script collects data and saves the
data for one week. Another useful feature of sar is that the output can be specific
about the usage for each processor in a multiprocessor environment, as seen in
the following output. The last line is an average output.
# sar -P ALL 2 1
AIX client1 3 4 000BC6DD4C00
07/06/00
14:46:52 cpu
14:46:54 0
1
2
3
-
%wio
0
0
0
0
0
%usr
0
0
0
0
0
%sys
0
1
0
0
0
%idle
100
99
100
100
100
More information on the sar command can be found in 3.1, “The sar command”
on page 40.
12
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Occasionally, the time spent in an application execution or an application startup
can be useful to have as reference material. The time command can be used for
this.
2.3 The time command
Use the time command to understand the performance characteristics of a single
program and its synchronous children. It reports the real time, that is, the elapsed
time from beginning to end of the program. It also reports the amount of CPU
time used by the program. The CPU time is divided into user and sys
components. The user value is the time used by the program itself and any
library subroutines it calls. The sys value is the time used by system calls
invoked by the program (directly or indirectly). An example output follows:
# time ./tctestprg4
real
0m5.08s
user
0m1.00s
sys
0m1.59s
The sum of user + sys is the total direct CPU cost of executing the program. This
does not include the CPU costs of parts of the kernel that can be said to run on
behalf of the program, but which do not actually run on the program’s thread. For
example, the cost of stealing page frames to replace the page frames taken from
the free list when the program started is not reported as part of the program's
CPU consumption. Another example of the time command is provided in 7.1,
“CPU performance scenario” on page 250.
When starting to analyze a performance problem, most analysts start with the
vmstat command, because it provides a brief overall picture of both CPU and
memory usage.
2.3.1 The vmstat command
The vmstat command reports statistics about kernel threads, virtual memory,
disks, traps, and CPU activity. Reports generated by the vmstat command can
be used to balance system load activity. These system-wide statistics (among all
processors) are calculated as averages for values expressed as percentages,
and as sums otherwise. Most interesting from a CPU point of view are the
highlighted two left-hand columns and the highlighted four right-hand columns in
the following output:
# vmstat 2 4
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
Chapter 2. Performance tuning: Getting started
13
1
0
0
0
1
0
0
0
63572
63579
63579
63579
173221
173214
173214
173214
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
475
480
473
474
2625
3279
3157
3158
401
406
386
398
0
0
0
0
0
1
0
1
99
98
99
99
0
0
0
0
The r column shows threads in the R state, while the b column shows threads in
S state, as shown in Figure 2-2 on page 11. The four right-hand columns are a
breakdown in percentages of CPU time used on user threads, system threads,
CPU idle time (running the wait process), and CPU idle time when the system
had outstanding disk or NFS I/O requests. For further discussion on the vmstat
command, see 3.2, “The vmstat command” on page 53.
If a system has poor performance because of a lot of threads on the run queue or
many threads waiting for I/O, then the ps command output is useful to determine
which process has used the most CPU resources.
2.3.2 The ps command
The ps command is a flexible tool for identifying the programs that are running on
the system and the resources they are using. It displays statistics and status
information about processes on the system, such as process or thread ID, I/O
activity, CPU, and memory utilization. In 3.3, “The ps command” on page 61, the
ps command output relevant to a CPU tuning perspective is discussed.
When looking for a run-away process, the next step in the analysis is to find out
which part of the process uses the CPU. For this, a profiler is needed. The AIX
profiler of preference is tprof.
2.3.3 The tprof command
The tprof command can be run over a time period to trace the activity of the
CPU. The CPU utilization is divided into kernel, user, shared, and other to show
how many clock timer ticks were spent in each respective address space. If the
user column shows high values, application tuning may be necessary. More
information about the tprof command can be found in 3.4, “The tprof command”
on page 67.
When finding a process that cannot be optimized, another way to tune the
process is to lessen its priority in the run queue. This can be accomplished by
grouping processes together to be handled by AIX Version 4.3 Workload
Manager or by use of the nice and renice commands.
14
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
2.3.4 The nice and renice commands
The nice command can run a process at a priority lower than the process’
normal priority. You must have root user authority to run a process at a higher
priority. The priority of a process is often called its nice value, but while the
priority of a process is recalculated at every clock timer tick, the nice value is
stable and manipulated with the nice or renice commands. The nice value can
range from 0 to 39, with 39 being the lowest priority. For example, if a process
normally runs with a default nice value of 20, resetting the nice value with an
increment of 5 runs the process at a lower priority, 25, and the process may run
slower. More information about the priorities and nice values can be found in
6.1.1, “Priority calculation on AIX versions prior to 4.3.2” on page 207, 6.1.2,
“Priority calculation on AIX Version 4.3.2 and later” on page 210, and 6.3.2, “The
nice and renice commands” on page 218.
Finally, in the list of common performance tools, there is the schedtune
command. This command is mentioned last for a reason: Do not manipulate the
scheduler without thorough knowledge of the scheduler mechanism.
2.3.5 The schedtune command
The priority of most user processes varies with the amount of CPU time the
process has used recently. The CPU scheduler's priority calculations are based
on two variables, SCHED_R (the weighting factor) and SCHED_D (the decay
factor). More information about the scheduler and the schedtune command is
covered in 6.1, “The AIX scheduler” on page 206, and in 6.3.1, “The schedtune
command” on page 214.
2.4 Memory performance overview
Memory in AIX is handled by the Virtual Memory Manager (VMM). The Virtual
Memory Manager is a facility that makes real memory appear larger than its
physical size. The virtual memory system is composed of real memory plus
physical disk space where portions of memory that are not currently in use are
stored.
The physical part of the virtual memory is divided into three types of segments
that reflect where the data is stored. This is symbolized in Figure 2-3 on page 16.
Chapter 2. Performance tuning: Getting started
15
Figure 2-3 VMM segments from a client perspective
The three types of segments are as follows:
 Persistent segment
A persistent segment persists after use by a process and has (and uses)
permanent storage locations on disks. Files containing data or executable
programs are mapped to persistent segments. AIX accesses all files as
mapped files. This means that programs or file access are started with only a
few initial disk pages, which are copied into virtual storage segments. Further
pages are page-faulted in on demand.
 Working segment
A working segment is transitory and only exists during use by the owning
process. It has no permanent disk storage location and therefore is stored to
paging space if free page frames in real memory are needed. For example,
kernel text segments and the process stack are mapped onto working
segments.
 Client segment
A client segment is where the pages are brought in by CDRFS, NFS, or any
other remote file system.
16
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
A process can use all of these segments, but from a process perspective the
VMM is logically divided into:
 Code and data segments
The code segment is the executable. This could be placed in a persistent
(local) or a client (remote executable) segment. The data segment is data
needed for the execution, for example, the process environment.
 Private and shared segments
The private segment can be a working segment containing data for the
process, for example, global variables, allocated memory, and the stack.
Segments can also be shared among processes, for example, processes can
share code segments, yet have private data segments.
The relationship between the segments is shown in Figure 2-4.
Figure 2-4 VMM segments from a process perspective
From a process point of view, the memory is further divided into 16 segments,
each pointed to by a segment register. These segment registers are hardware
registers located on the processor. When a process is active, the registers
contain the addresses of the 16 segments addressable by that process. Each
segment contains a specific set of information. A generic example is shown in
Figure 2-5 on page 18.
Chapter 2. Performance tuning: Getting started
17
Figure 2-5 VMM memory registers
Each segment is further divided into 4069-byte pages of information. Each page
sits on a 4 KB partition of the disk known as a slot. The VMM is responsible for
allocating real memory page frames and resolving references to pages that are
not currently in memory. In other words, when the system needs to reference a
page that is not currently in memory, the VMM is responsible for finding and
resolving the reference of the disk frame.
The VMM maintains a list of free page frames that is used to accommodate
pages that must be brought into memory. In memory-constrained environments,
the VMM must occasionally replenish the free list by moving some of the current
data from real memory. This is called page stealing. A page fault is a request to
load a 4-KB data page from disk. A number of places are searched in order to
find data.
First, the data and instruction caches are searched. Next, the Translation
Lookaside Buffer (TLB) is searched. This is an index of recently used virtual
addresses with their page frame IDs. If the data is not in the TLB, the Page
Frame Table (PTF) is consulted. This is an index for all real memory pages, and
this index is held in pinned memory. The table is large; therefore, there are
18
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
indexes to this index. The Hash Anchor Table (HAT) links pages of related
segments in order to get a faster entry point to the main PTF.
To the page stealer, memory is divided into computational memory and file
memory.
 Computational memory consists of pages that belong to the working segment
or program text segment.
 File memory consists of the remaining pages. These are usually pages from
the permanent data file in persistent memory.
The page stealer tries to balance these two types of memory usage when
stealing pages. The page replacement algorithm can be manipulated.
When starting a process, a slot is assigned, and when a process references a
virtual memory page that is on the disk, the referenced page must be paged in
and probably one or more pages must be paged out, creating I/O traffic and
delaying the start up of the process. AIX attempts to steal real memory pages
that are unlikely to be referenced in the near future, using a page replacement
algorithm. If the system has too little memory, no RAM pages are good
candidates to be paged out, as they will be reused in the near future. When this
happens, continuous page in and page out occurs. This condition is called
thrashing.
When discussing memory, the allocation algorithm is commonly mentioned. The
following is a discussion from AIX Version 4.3 System Management Concepts:
Operating System and Devices, SC23-4311, on the allocation algorithm:
The operating system uses the PSALLOC environment variable to determine
the mechanism used for memory and paging space allocation. If the
PSALLOC environment variable is not set, is set to null, or is set to any value
other than early, the system uses the default late allocation algorithm.
The late allocation algorithm does not reserve paging space when a memory
request is made; it approves the request and assigns paging space when
pages are touched. Some programs allocate large amounts of virtual memory
and then use only a fraction of the memory. Examples of such programs are
technical applications that use sparse vectors or matrices as data structures.
The late allocation algorithm is also more efficient for a real-time,
demand-paged kernel such as the one in the operating system.
For AIX Version 4.3.2 and later, the late allocation algorithm is modified to
further delay the allocation of paging space. As mentioned previously, before
AIX Version 4.3.2, paging space was allocated when a page was touched.
However, this paging space may never be used, especially on systems with
large real memory where paging is rare. Therefore, the allocation of paging
space is delayed until it is necessary to page out the page, which results in no
Chapter 2. Performance tuning: Getting started
19
wasted paging space allocation. This does result, however, in additional
over-commitment of paging space. On a system where enough virtual
memory is accessed that paging is necessary, the amount of paging space
required may be as much as was required on previous releases.
It is possible to overcommit resources when using the late allocation
algorithm for paging space allocation. In this case, when one process gets the
resource before another, a failure results. The operating system attempts to
avoid complete system failure by killing processes affected by the resource
over-commitment. The SIGDANGER signal is sent to notify processes that
the amount of free paging space is low. If the paging space situation reaches
an even more critical state, selected processes that did not receive the
SIGDANGER signal are sent a SIGKILL signal.
The user can use the PSALLOC environment variable to switch to an early
allocation algorithm for memory and paging space allocation. The early
allocation mechanism allocates paging space for the executing process at the
time the memory is requested. If there is insufficient paging space available at
the time of the request, the early allocation mechanism fails the memory
request.
The new paging space allocation algorithm introduced with AIX Version 4.3.2 is
also named Deferred Page Space Allocation (DPSA). After a page has been
paged out to paging space, the disk block is reserved for that page if that page is
paged back into RAM. Therefore, the paging space percentage-used value may
not necessarily reflect the number of pages only in the paging space, because
some of them may be back in RAM. If the page that was paged back in is the
working storage of a thread, and if the thread releases the memory associated
with that page or if the thread exits, then the disk block for that page is released.
This affects the output for the ps command and the svmon command on Version
4.3.3. For more information on the differences between AIX Version 4.3.2 and
Version 4.3.3 refer to AIX Version 4.3 System Management Concepts: Operating
System and Devices, SC23-4311.
When working with memory performance tuning, the first command to use is
usually the vmstat command.
2.4.1 The vmstat command
The vmstat command summarizes the total active virtual memory used by all of
the processes running on the system, as well as the number of real-memory
page frames on the free list. Active virtual memory is defined as the number of
virtual-memory working segment pages that actually have been touched. This
number can be larger than the number of real page frames in the machine
because some of the active virtual-memory pages may have been written out to
paging space.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
When determining if a system is short on memory or if some memory tuning is
required, use the vmstat command over a set interval and examine the pi and po
columns on the resulting report. These columns indicate the number of paging
space page-ins per second and the number of paging space page-outs per
second. If the values are constantly non-zero, there may be a memory
bottleneck. Having occasional non-zero values is not a concern, because paging
is the main principle of virtual memory.
From a VMM tuning perspective, the middle (highlighted) columns are the most
interesting. They provide information about the use of virtual and real memory
and information about page faults and paging activity.
# vmstat 2 4
kthr memory
----- ----------r b avm
fre
0 0 16590 14475
0 1 16590 14474
0 1 16590 14474
0 1 16590 14474
page
-----------------------re pi po fr sr cy
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
faults
-----------in
sy
cs
101 9
8
408 2232 48
406 43
40
405 91
39
cpu
----------us sy id wa
50 0 50 0
0 0 99 0
0 0 99 0
0 0 99 0
The highlighted columns are described Table 2-3.
Table 2-3 VMM-related output from the vmstat command
Column
Description
avm
Active virtual pages
fre
Size of the free list
re
Pager input/output list
pi
Pages paged in from paging space
po
Pages paged out to paging space
fr
Pages freed (page replacement)
sr
Pages scanned by page-replacement algorithm
cy
Clock cycles by page-replacement algorithm
For more information about the vmstat command, see 3.2, “The vmstat
command” on page 53.
Note: A large portion of real memory is utilized as a cache for file system data.
It is not unusual for the size of the free list to remain small.
Chapter 2. Performance tuning: Getting started
21
Another tool used in the initial phase of VMM tuning is the ps command.
2.4.2 The ps command
The ps command can also be used to monitor the memory usage of individual
processes. The ps v PID command provides the most comprehensive report on
memory-related statistics for an individual process, as discussed in 3.3, “The ps
command” on page 61.
In the previous discussion, the paging space function of VMM was mentioned.
The lsps command is an useful tool to check paging-space utilization.
2.4.3 The lsps command
The lsps command displays the characteristics of paging spaces, such as the
paging-space name, physical-volume name, volume-group name, size,
percentage of the paging space used, whether the space is active or inactive,
and whether the paging space is set to be automatically initiated at system boot.
The following is an example of the lsps command using the -a flag. The -s flag is
useful when a summary and total percentage used over several disks is required.
# lsps -a
Page Space
hd6
Physical Volume
hdisk2
Volume Group
rootvg
Size
1024MB
%Used
1
Active Auto Type
yes
yes
lv
When finding problems with memory usage, the svmon command provides a
more detailed report on what processes are using what segments of memory.
2.4.4 The svmon command
The svmon command provides a more in-depth analysis of memory usage. It is
more informative, but also more intrusive, than the vmstat and ps commands.
The svmon command captures a snapshot of the current state of memory. There
are some significant changes in the flags and in the output from the svmon
command between AIX Version 4.3.2 and Version 4.3.3. This is discussed in
more detail in 3.5, “The svmon command” on page 70.
The command to use when tuning memory management is the vmtune
command.
2.4.5 The vmtune command
The memory management algorithm tries to keep the size of the free list and the
percentage of real memory occupied by persistent segment pages within
specified bounds. These bounds can be altered with the vmtune command, which
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
can only be run by the root user. Changes made by this tool remain in effect until
the next system reboot. More information on the vmtune command can be found
in 6.5, “The vmtune command” on page 222.
To test how much (or, perhaps, little) memory is needed for a certain server load,
use the rmss command.
2.4.6 The rmss command
The rmss command simulates a system with various sizes of real memory,
without having to extract and replace memory boards. By running an application
at several memory sizes and collecting performance statistics, you can
determine the memory needed to run an application with acceptable
performance. The rmss command can be invoked for the following purposes.
 To change the memory size and then exit. This lets you experiment freely
with a given memory size.
 To function as a driver program. In this mode, the rmss command executes a
specified command multiple times over a range of memory sizes, and
displays important statistics describing command performance at each
memory size. The command can be an executable or shell script file, with or
without command line arguments.
2.5 Disk I/O performance overview
The set of operating system commands, library subroutines, and other tools that
allow you to establish and control logical volume storage is called the Logical
Volume Manager (LVM). The LVM controls disk resources by mapping data
between simple and flexible logical views of storage space and the physical
disks. The LVM does this using a layer of device driver code that runs above
traditional disk device drivers.
The LVM consists of the logical volume device driver (LVDD) and the LVM
subroutine interface library. The logical volume device driver is a pseudo-device
driver that manages and processes all I/Os. It translates logical addresses into
physical addresses and sends I/O requests to specific device drivers. When a
process requests a disk read or write, the operation involves the file system,
VMM, and LVM, as shown in Figure 2-6 on page 24.
Chapter 2. Performance tuning: Getting started
23
Figure 2-6 Logical volume device driver
Each individual disk drive, called a physical volume (PV), is named, such as
/dev/hdisk0. If the physical volume is in use, it belongs to a volume group (VG).
All of the physical volumes in a volume group are divided into physical partitions
(PPs) of the same size (by default, 4 MB in volume groups that include physical
volumes smaller than 4 GB; 8 MB or more with larger disks).
Within each volume group, one or more logical volumes (LVs) are defined. Each
logical volume consists of one or more logical partitions. Each logical partition
corresponds to at least one physical partition. If mirroring is specified for the
logical volume, additional physical partitions are allocated to store the additional
copies of each logical partition. Although the logical partitions are numbered
consecutively, the underlying physical partitions are not necessarily consecutive
or contiguous.
Figure 2-7 on page 25 shows the relationship and dependencies between the
logical picture of the volume group with its corresponding physical layout.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure 2-7 Dependencies in a volume group
Logical volumes can serve a number of system purposes, such as paging, but
each logical volume that holds ordinary system data, user data, or programs
contains a single journaled file system (JFS). Each JFS consists of a pool of
page-size (4096-byte) blocks. When data is written to a file, one or more
additional blocks are allocated to that file. These blocks may or may not be
contiguous with one another and with other blocks previously allocated to the file.
In AIX Version 4, a given file system can be defined as having a fragment size of
less than 4096 bytes. A fragment size can be set to 512, 1024, or 2048 bytes,
allowing small files to be stored more efficiently.
While an operating system's file is conceptually a sequential and contiguous
string of bytes, the physical reality is very different. Fragmentation may arise
from multiple extensions to logical volumes, as well as
allocation/release/reallocation activity within a file system. A file system is
fragmented when its available space consists of large numbers of small chunks
of space, making it impossible to write out a new file in contiguous blocks.
Access to files in a highly fragmented file system may result in a large number of
seeks and longer I/O response times (seek latency dominates I/O response
Chapter 2. Performance tuning: Getting started
25
time). For example, if the file is accessed sequentially, a file placement that
consists of many widely separated chunks requires more seeks than a
placement that consists of one or a few large contiguous chunks.
If the file is accessed randomly, a placement that is widely dispersed requires
longer seeks than a placement where the file's blocks are close together.
The VMM tries to anticipate the future need for pages of a sequential file by
observing the pattern a program uses to access the file. When the program
accesses two successive pages of the file, the VMM assumes that the program
will continue to access the file sequentially, and the VMM schedules additional
sequential reads of the file. This is called Sequential-Access Read Ahead. These
reads are overlapped with the program processing, and will make the data
available to the program sooner than if the VMM had waited for the program to
access the next page before initiating the I/O. The number of pages to be read
ahead is determined by two VMM thresholds:
minpgahead
A number of pages read ahead when the VMM first
detects the sequential access pattern. If the program
continues to access the file sequentially, the next read
ahead will be for 2 x minpgahead, the next for 4 x
minpgahead, and so on until the number of pages
reaches maxpgahead.
maxpgahead
A maximum number of pages the VMM will read ahead in
a sequential file.
If the program deviates from the sequential-access pattern and accesses a page
of the file out of order, sequential read ahead is terminated. It will be resumed
with minpgahead pages if the VMM detects a resumption of sequential access by
the program. The values of minpgahead and maxpgahead can be set with the
vmtune command. More information on the vmtune command can be found in 6.5,
“The vmtune command” on page 222.
To increase write performance, limit the number of dirty file pages in memory,
reduce system overhead, and minimize disk fragmentation, the file system
divides each file into 16 KB partitions. The pages of a given partition are not
written to disk until the program writes the first byte of the next 16 KB partition. At
that point, the file system forces the four dirty pages of the first partition to be
written to disk. The pages of data remain in memory until their frames are
reused. If a program accesses any of the pages before their frames are reused,
no I/O is required.
If a large number of dirty file pages remains in memory and do not get reused,
the sync daemon writes them to disk, which may result in abnormal disk
utilization. To distribute the I/O activity more efficiently across the workload,
write-behind can be turned on to tell the system how many pages to keep in
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
memory before writing them to disk. The write-behind threshold is on a per-file
basis, which causes pages to be written to disk before the sync daemon runs.
The I/O is spread more evenly throughout the workload.
There are two types of write-behind: Sequential and random. The size of the
write-behind partitions and the write-behind threshold can be changed with the
vmtune command.
Normal files are automatically mapped to segments to provide mapped files. This
means that normal file access bypasses traditional kernel buffers and block I/O
routines, allowing files to use more memory when the extra memory is available
(file caching is not limited to the declared kernel buffer area).
Because most writes are asynchronous, FIFO I/O queues of several megabytes
can build up, which can take several seconds to complete. The performance of
an interactive process is severely impacted if every disk read spends several
seconds working its way through the queue. In response to this problem, the
VMM has an option called I/O pacing to control writes.
I/O pacing does not change the interface or processing logic of I/O. It simply
limits the number of I/Os that can be outstanding against a file. When a process
tries to exceed that limit, it is suspended until enough outstanding requests have
been processed to reach a lower threshold.
Disk-I/O pacing is intended to prevent programs that generate very large
amounts of output from saturating the system's I/O facilities and causing the
response times of less-demanding programs to deteriorate. Disk-I/O pacing
enforces per-segment (which effectively means per-file) high and low water
marks on the sum of all pending I/Os. When a process tries to write to a file that
already has high water mark pending writes, the process is put to sleep until
enough I/Os have completed to make the number of pending writes less than or
equal to the low water mark. The logic of I/O-request handling does not change.
The output from high-volume processes is slowed down somewhat.
When gathering information on I/O performance, the first command to use is the
iostat command.
2.5.1 The iostat command
The iostat command is used for monitoring system input/output device loading
by observing the time the physical disks are active in relation to their average
transfer rates. This command generates reports that can be used to change the
system configuration to better balance the input/output load between physical
disks and adapters. The iostat command gathers its information on the protocol
layer.
Chapter 2. Performance tuning: Getting started
27
AIX Version 4.3.3 and later contain enhancements to the method used to
compute the percentage of CPU time spent waiting on disk I/O (wio time). The
method used in AIX Version 4.3.2 and earlier versions of the operating system
can, under certain circumstances, give an inflated view of wio time on SMPs. The
wio time is reported by the commands sar (%wio), vmstat (wa), and iostat
(% iowait).
In AIX Version 4.3.2 and earlier, at each clock timer tick interrupt on each
processor (100 times a second per processor), a determination is made as to
which of the four categories (usr/sys/wio/idle) to place the last 10 ms of time. If
the CPU was busy in usr mode at the time of the clock interrupt, then usr gets the
clock tick added into its category. If the CPU was busy in kernel mode at the time
of the clock interrupt, then the sys category gets the tick. If the CPU was not
busy, a check is made to see if any I/O-to-disk is in progress. If it is in progress,
the wio category is incremented. If no disk I/O is in progress and the CPU is not
busy, the idle category gets the tick.
The inflated view of wio time results from all idle CPUs being categorized as wio
regardless of the number of threads waiting on I/O. For example, systems with
just one thread doing I/O could report over 90 percent wio time, regardless of the
number of CPUs it has.
The change in AIX Version 4.3.3 is to mark only an idle CPU as wio if an
outstanding I/O was started on that CPU. This method can report much lower wio
times when just a few threads are doing I/O and the system is otherwise idle. For
example, a system with four CPUs and one thread doing I/O will report a
maximum of 25 percent wio time. A system with 12 CPUs and one thread doing
I/O will report a maximum of 8.3 percent wio time.
Also, NFS now goes through the buffer cache and waits in those routines are
accounted for in the wa statistics.
Another change is that the wa column details the percentage of time the CPU
was idle with pending disk I/O to not only local, but also NFS-mounted disks.
More information about the iostat command can be found in 4.2, “The iostat
command” on page 118.
When experiencing performance problems due to disk I/O, the next step is to find
the file system causing the problem. This can be done with the filemon
command.
2.5.2 The filemon command
The filemon command uses the trace facility to obtain a detailed picture of I/O
activity during a time interval on the various layers of file system utilization,
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
including the logical file system, virtual memory segments, LVM, and physical
disk layers. Both summary and detailed reports are generated. More information
about the filemon command can be found in 4.5.1, “The filemon command” on
page 141.
If a file is identified as the problem, the fileplace command can be used to see
how the file is stored.
2.5.3 The fileplace command
The fileplace command displays the placement of a specified file within the
logical or physical volumes containing the file. By default, the fileplace
command lists, to standard output, the ranges of logical volume fragments
allocated to the specified file. More information about the fileplace command
can be found in 4.6.2, “Enhanced journaled file system (JFS2)” on page 152.
If a logical volume is identified as a problem, the lslv command can provide
useful information.
2.5.4 The lslv command
The lslv command shows, among other information, the logical volume
fragmentation. If the workload shows a significant degree of I/O dependency, you
can use the lslv command to investigate the physical placement of the files on
the disk to determine if reorganization at some level would yield an improvement.
More information about the lslv command can be found in 4.4.2, “Logical
volume fragmentation” on page 138, and 4.9.3, “The lslv command” on
page 165.
2.6 Network performance overview
When performance problems arise and you look for the cause, your local system
may not have a problem, while the real problem is buildings away. An easy way
to tell if the network is affecting overall performance is to compare those
operations that involve the network with those that do not. If you are running a
program that does a considerable amount of remote reads and writes and it is
running slowly, but everything else seems to be running normally, then it is
probably a network problem. Some of the potential network bottlenecks can be
caused by the following:
 Client-network interface
 Network bandwidth
 Network topology
Chapter 2. Performance tuning: Getting started
29
 Server network interface
 Server CPU load
 Server memory usage
 Server bandwidth
 Inefficient configuration
A large part of network tuning involves tuning TCP/IP to achieve maximum
throughput. With the high-bandwidth interfaces such as FIDDI and Gigabit
Ethernet, this has become even more important. Before attempting to tune
network parameters, it helps to understand their use in the processing layer they
affect. Figure 2-8 shows the layers involved in a read or write activity across
TCP/IP and provides the network parameters used in each layer.
Figure 2-8 Network parameters
Chapter 5, “Network performance tools” on page 171, discusses, in more detail,
how to set mbufs and clusters, network packet settings, and adapter settings for
network performance tuning.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The first command to use for gathering information on network performance is
the netstat command.
2.6.1 The netstat command
The netstat command symbolically displays the contents of various
network-related data structures for active connections. The netstat command
can also provide useful information on a per-protocol basis. For more information
on the netstat command, see 5.4.3, “The netstat command” on page 180.
If the performance problem is due to NFS load, the nfsstat command is useful.
2.6.2 The nfsstat command
NFS gathers statistics on types of NFS operations performed, along with error
information and performance indicators. You can use the nfsstat command to
identify network problems and observe the type of NFS operations taking place
on your system. The nfsstat command displays statistical information about the
NFS and Remote Procedure Call (RPC) interfaces to the kernel. The nfsstat
command splits its information into server and client parts. For example, use the
command:
 netstat -r to see how an application uses NFS
The output is divided into server connection- and connectionless-oriented, as
well as client connection- and connectionless-oriented.
 nfsstat -s to see the server report
The NFS server displays the number of NFS calls received (calls) and
rejected (badcalls) due to authentication, as well as the counts and
percentages for the various kinds of calls made.
 nfsstat -c to see the client part
The NFS client displays the number of calls sent and rejected, as well as the
number of times a client handle was received (clgets) and a count of the
various kinds of calls and their respective percentages. For performance
monitoring, the nfsstat -c command provides information on whether the
network is dropping UDP packets. A network may drop a packet if it cannot
handle it. Dropped packets can be the result of the response time of the
network hardware or software or an overloaded CPU on the server. Dropped
packets are not actually lost, because a replacement request is issued for
them.
A high badxid count implies that requests are reaching the various NFS
servers, but the servers are too loaded to send replies before the client's RPC
calls time out and are retransmitted. The badxid value is incremented each
Chapter 2. Performance tuning: Getting started
31
time a duplicate reply is received for a transmitted request (an RPC request
retains its XID through all transmission cycles). Excessive retransmissions
place an additional strain on the server, further degrading response time.
The retrans column displays the number of times requests were retransmitted
due to a time-out while waiting for a response. This situation is related to
dropped UDP packets. If the retrans number consistently exceeds five
percent of the total calls in column one, it indicates a problem with the server
keeping up with demand.
For example, to display the number of RPC and NFS call-related information for
the client and server, enter:
# nfsstat -rs
Server rpc:
Connection oriented
calls
badcalls
0
0
Connectionless
calls
badcalls
0
0
nullrecv
0
badlen
0
xdrcall
0
dupchecks
0
dupreqs
0
nullrecv
0
badlen
0
xdrcall
0
dupchecks
0
dupreqs
0
RPC output for the server is as follows:
calls
Total number of RPC calls received from clients.
badcalls
Total number of calls rejected by the RPC layer.
nullrecv
Number of times an RPC call was not available when it
was thought to be received. If the number starts to grow, it
may mean there are too many nfsd daemons.
badlen
Packets truncated or damaged (number of RPC calls with
a length shorter than a minimum-sized RPC call).
xdrcall
Number of RPC calls whose header could not be External
Data Representation (XDR) decoded.
dupchecks
Number of RPC calls looked up in the duplicate request
cache.
dupreqs
Number of duplicate RPC calls found.
When requiring a more detailed output, the netpmon command, a trace facility, is
useful.
2.6.3 The netpmon command
The netpmon command monitors a trace of system events, and reports on
network activity and performance during the monitored interval. By default, the
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
netpmon command runs in the background while one or more application
programs or system commands are being executed and monitored. The netpmon
command automatically starts and monitors a trace of network-related system
events in real time. More information on the netpmon command can be found in
Chapter 5, “Network performance tools” on page 171.
2.7 The performance diagnostic tool (PDT)
The performance diagnostic tool attempts to identify performance problems
automatically by collecting and integrating a wide range of performance,
configuration, and availability data. The data is regularly evaluated to identify and
anticipate common performance problems.
PDT assesses the current state of a system and tracks changes in workload and
performance. It attempts to identify incipient problems and suggests solutions
before the problems become critical.
For the most part, PDT functions with no required user input. PDT data collection
and reporting are easily enabled, and then no further administrator activity is
required. Periodically, data is collected and recorded for historical analysis, and a
report is produced and mailed to the adm user. Normally, only the most
significant apparent problems are recorded on the report. If there are no
significant problems, that fact is reported. PDT can be customized to direct its
report to a different user or to report apparent problems of a lower severity level.
2.7.1 Installing and enabling PDT
PDT is installed through the installp command as the bos.perf.diag_tool fileset.
PDT must be enabled in order to begin collecting data and writing reports.
Enable PDT by executing the /usr/sbin/perf/diag_tool/pdt_config script. Only the
root user is permitted to run this script.
The following example shows the message displayed when the
/usr/sbin/perf/diag_tool/pdt_config script is run:
# /usr/sbin/perf/diag_tool/pdt_config
________________PDT customization menu__________________
1)
2)
3)
4)
5)
6)
7)
show current PDT
modify/enable PDT
disable
PDT
modify/enable PDT
disable
PDT
de-install
PDT
exit pdt_config
report recipient and severity level
reporting
reporting
collection
collection
Chapter 2. Performance tuning: Getting started
33
Please enter a number:
When you respond with 4, default PDT collection and reporting is enabled. The
crontab entry for user adm is updated to add the PDT entries. The entries
execute a shell script called Driver_ in the /usr/sbin/perf/diag_tool directory. This
script is passed to three different parameters, each representing a collection
profile, at three different collection times. To terminate the pdt_config program,
respond with 7. To disable collection, respond with 5.
Table 2-4 lists the performance diagnostic tool’s configurable attributes.
Table 2-4 The performance diagnostic tool
PDT configurable
attribute
PDT configuration method
PDT report recipient
Execute the /usr/sbin/perf/diag_tool/pdt_config script.
PDT security level
Execute the /usr/sbin/perf/diag_tool/pdt_config script.
PDT report on demand
Execute the /usr/sbin/perf/diag_tool/pdt_report script.
List of files monitored by
PDT
Edit the /var/perf/cfg/diag_tool/.files file.
Modifying the list of hosts
monitored by PDT
Edit the /var/perf/cfg/diag_tool/.nodes file.
Historical-record retention
period for PDT reports
Edit the /var/perf/cfg/diag_tool/.retention.list.
PDT collection, retention,
and reporting times
Use the /var/perf/cfg/diag_tool/.collection.control file.
Use the /var/perf/cfg/diag_tool/.retention.control file.
Use the /var/perf/cfg/diag_tool/.reporting.control file.
The default time can be changed by altering the crontab
for user adm.
PDT thresholds
Uses the /var/perf/cfg/diag_tool/.thresholds file.
PDT error reporting
View the /var/perf/tmp/.stderr file.
Uninstalling PDT
Execute the /usr/sbin/perf/diag_tool/pdt_config script
Use installp to remove the bos.perf.diag_tool fileset.
2.8 Service level agreement
To allow the service provider and the client to manage the environment, a
service level agreement should be created.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
A service level agreement (SLA) is a contract between a service provider and a
client that specifies, usually in measurable terms, what service the service
provider will furnish. The service level agreement should include the following
metrics in order to safeguard the service provider and the customer, for example:
 Reporting policies
 Roles and responsibilities
 What percentage of the time service will be available
 The number of users that can be served simultaneously
 Specific performance benchmarks to which actual performance will be
periodically compared
 Goals and objectives
 The schedule for notification in advance of changes that may affect users
 Help desk response time for various classes of problems
 Penalties
 Dial-in access availability
 Usage statistics that will be provided
 Incentives
2.9 Summary
Figure 2-1 on page 10 (shown in the beginning of this chapter) is used in the
summary (Figure 2-9 on page 36). It is modified to include performance
suggestions.
Chapter 2. Performance tuning: Getting started
35
Figure 2-9 Performance tuning flowchart
2.10 Quiz
The following assessment question helps verify your understanding of the topics
discussed in this chapter.
1. When paging, cache, and Translation Lookaside Buffer (TLB) metrics or
statistics are analyzed for performance, which of the following resources is
being analyzed?
36
A.
CPU
B.
Memory
C.
Disk I/O
D.
Network I/O
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
2.10.1 Answers
The following is the preferred answer to the question provided in this section.
1. B
Chapter 2. Performance tuning: Getting started
37
38
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
3
Chapter 3.
CPU and memory
performance monitoring
tools
This chapter takes a detailed look at several CPU and memory performance
monitoring tools. The provided examples will assist you in culling the valuable
information from the verbose output generated by these tools.
© Copyright IBM Corp. 2002. All rights reserved.
39
3.1 The sar command
The sar command (System Activity Report) can be used in two ways to collect
data: One is to view system data in real time, and the other is to view data
previously captured.
The sar command is one of the first performance monitors to be used by an
administrator. Although the sar command does give useful information on most
system functions, it should be noted that there are other tools that will give more
accurate system utilization reports on specific sections within the environment.
3.1.1 Accounting software
The sar command requires the bos.perf.perfstat default installation fileset and
the bos.acct additional fileset to be installed. To view the files in bos.acct, type
the following command:
# lslpp -f bos.acct
3.1.2 Examples of using the sar command
The sar command, without any flags, will give an output of every line in the file
for the current day as collected by the sa1 command. The time slice can be set
up in the crontab file and. In the following example, it uses the default in the
/var/spool/cron/crontabs/adm file:
# sar
08:00:00
08:20:00
08:40:00
09:00:00
Average
%usr
0
0
0
%sys
0
0
0
%wio
0
0
0
%idle
100
100
100
0
0
0
100
The sar command, using only interval and number flags, will have the output
shown in the following example. This is the same as running the sar -u 1 10
command. The 1 specifies the interval in seconds and the 10 specifies the
number of times the data is captured.
# sar 1 10
AIX server2 3 4 000FA17D4C00
09:14:57
09:14:58
09:14:59
09:15:00
40
%usr
54
40
44
%sys
18
20
19
06/30/00
%wio
28
40
38
%idle
0
0
0
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
09:15:01
09:15:02
09:15:03
09:15:04
09:15:05
09:15:06
09:15:07
82
66
45
60
47
65
48
14
16
12
17
16
12
8
4
18
43
23
37
23
44
0
0
0
0
0
0
0
Average
55
15
30
0
The sar -a command reports the use of file access system routines specifying
how many times per second several of the system file access routines have been
called.
# sar -a 1 10
AIX server2 3 4 000FA17D4C00
09:28:44
09:28:45
09:28:46
09:28:47
09:28:48
09:28:49
09:28:50
09:28:51
09:28:52
09:28:53
09:28:54
06/30/00
iget/s lookuppn/s dirblk/s
0
1169
277
0
15
0
0
50
0
0
559
19
0
390
20
0
1467
137
0
1775
153
0
2303
74
0
2832
50
0
883
44
Average
0
1144
77
The sar -c command reports system calls.
# sar -c 1 10
AIX server2 3 4 000FA17D4C00
09:33:04 scall/s sread/s swrit/s
09:33:05
1050
279
118
09:33:06
186
19
74
09:33:07
221
19
79
09:33:08
2996
132
400
09:33:09
3304
237
294
09:33:10
4186
282
391
09:33:11
1938
109
182
09:33:12
3263
179
303
09:33:13
2751
172
258
09:33:14
2827
187
285
06/30/00
fork/s
0.00
0.00
0.00
0.00
0.00
0.00
1.00
0.00
0.00
0.00
exec/s rchar/s wchar/s
0.00 911220 5376749
0.00
3272 3226417
0.00
3272 3277806
0.00 314800 2284933
0.00 167733 848174
0.00 228196 509414
1.00 153703 1297872
0.00 242048 1003364
0.00 155082 693801
0.00 174059 1155239
Chapter 3. CPU and memory performance monitoring tools
41
Average
2273
162
238
0.10
0.10
235271 1966259
The sar -d command reads disk activity with read and write and block size
averages. This flag is not documented in the AIX documentation, but is used by
some AIX gurus. Use the iostat command instead of the sar -d command.
# sar -d 5 3
AIX server2 3 4 000FA17D4C00
06/30/00
10:08:19
device
%busy
avque
10:08:24
hdisk0
hdisk1
cd0
0
0
0
10:08:29
hdisk0
hdisk1
cd0
10:08:34
Average
r+w/s
blks/s
avwait
avserv
0.0
0.0
0.0
0
0
0
4
3
0
0.0
0.0
0.0
0.0
0.0
0.0
44
36
0
1.0
0.0
0.0
366
47
0
3569
2368
0
0.0
0.0
0.0
0.0
0.0
0.0
hdisk0
hdisk1
cd0
84
16
0
2.0
1.0
0.0
250
19
0
1752
950
0
0.0
0.0
0.0
0.0
0.0
0.0
hdisk0
hdisk1
cd0
42
17
0
1.0
0.3
0.0
205
22
0
1775
1107
0
0.0
0.0
0.0
0.0
0.0
0.0
The sar -q command reports queue statistics.
# sar -q 1 10
AIX server2 3 4 000FA17D4C00
06/30/00
11:08:33 runq-sz %runocc swpq-sz %swpocc
11:08:34
1.0
100
11:08:35
1.0
100
11:08:36
1.0
100
11:08:37
1.0
100
11:08:38
1.0
100
1.0
100
11:08:39
1.0
100
1.0
100
11:08:40
1.0
100
1.0
100
11:08:41
1.0
100
11:08:42
1.0
100
11:08:43
1.0
100
Average
42
1.0
50
1.0
80
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The sar -r command reports paging statistics.
# sar -r 1 10
AIX server2 3 4 000FA17D4C00
06/30/00
11:16:11
11:16:12
11:16:13
11:16:14
11:16:15
11:16:16
11:16:17
11:16:18
11:16:19
11:16:20
11:16:21
slots cycle/s fault/s odio/s
130767
0.00 472.82
66.02
130767
0.00 989.00 800.00
130767
0.00
44.00 1052.00
130767
0.00
43.00 1040.00
130767
0.00
47.00 1080.00
130767
0.00
43.00 808.00
130767
0.00
40.00 860.00
130767
0.00
46.00 836.00
130767
0.00
47.00 852.00
130767
0.00
48.00 836.00
Average
130767
0
183
821
The sar -v command reports the status of the process, kernel-thread, inode, and
file tables.
# sar -v 1 5
AIX server2 3 4 000FA17D4C00
11:12:39
11:12:40
11:12:41
11:12:42
11:12:43
11:12:44
proc-sz
49/262144
46/262144
45/262144
45/262144
45/262144
inod-sz
229/42942
221/42942
220/42942
220/42942
220/42942
06/30/00
file-sz
315/511
303/511
301/511
301/511
301/511
thrd-sz
59/524288
56/524288
55/524288
55/524288
55/524288
The sar -y command reports TTY device activity per second.
# sar -y 1 10
AIX server2 3 4 000FA17D4C00
06/30/00
11:48:36 rawch/s canch/s outch/s rcvin/s xmtin/s mdmin/s
11:48:37
0
0
104
63
60
0
11:48:38
0
0
58
9
60
0
11:48:39
0
0
58
69
61
0
11:48:40
0
0
58
68
60
0
11:48:41
0
0
58
69
3
0
11:48:42
0
0
58
68
52
0
11:48:43
0
0
58
69
60
0
11:48:44
0
0
58
25
60
0
11:48:45
0
0
58
42
23
0
Chapter 3. CPU and memory performance monitoring tools
43
11:48:46
0
0
58
68
9
0
Average
0
0
63
55
45
0
Although this is not an exhaustive list of the sar command and command output,
it is an indication of what the main flags can do. When running the sar command,
a combination of the flags can be used to obtain the output required for analyses,
as in the following example:
# sar -y -r 1 5
AIX server2 3 4 000FA17D4C00
06/30/00
11:48:56 rawch/s canch/s outch/s rcvin/s xmtin/s mdmin/s
slots cycle/s fault/s odio/s
11:48:57
0
130767
0
0.00
147
3.96
67
0.00
3
0
11:48:58
0
130767
0
0.00
102
0.00
69
0.00
58
0
11:48:59
0
130767
0
0.00
102
0.00
68
0.00
60
0
11:49:00
0
130767
0
0.00
102
0.00
69
0.00
17
0
11:49:01
0
130767
0
0.00
102
1.00
68
4.00
3
0
Average
Average
0
130767
0
0
111
1
68
1
28
0
3.1.3 The sar command summary
The sar command writes the contents of selected cumulative activity counters in
the operating system to standard output.
The sar command syntax is as follows:
sar [ { -A | [ -a ] [ -b ] [ -c ] [ -k ] [ -m ] [ -q ] [ -r ] [ -u ] [ -v ]
[ -w ] [ -y ] } ] [ -P ProcessorIdentifier, ... | ALL ]
[ -ehh [ :mm [ :ss ] ] ] [ -fFile ] [ -iSeconds ] [ -oFile ]
[ -shh [ :mm [ :ss ] ] ] [ interval [ number ] ]
The accounting system, based on the values in the interval and number
parameters, writes information at the specified intervals in seconds the specified
number of times. The default sampling interval for the number parameter is 1
44
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
second. The collected data can also be saved in the file specified by the -o file
flag.
If CPU utilization is near 100 percent (user + system), the workload sampled is
CPU-bound. If a considerable percentage of time is spent in I/O wait, it implies
that CPU execution is blocked while waiting for disk I/O. The I/O may be from file
accesses or it may be I/O associated with paging due to a lack of sufficient
memory.
Note: The time the system spends waiting for remote file access is not
accumulated in the I/O wait time. If CPU utilization and I/O wait time for a task
are relatively low, and the response time is not satisfactory, consider
investigating how much time is being spent waiting for remote I/O. Since no
high-level command provides statistics on remote I/O wait, trace data may be
useful in observing this.
The sar command calls a command named sadc to access system data. Two
shell scripts, /usr/lib/sa/sa1 and /usr/lib/sa/sa2, are structured to be run by the
cron command and provide daily statistics and reports. Sample stanzas are
included (but commented out) in the /var/spool/cron/crontabs/adm crontab file to
specify when the cron daemon should run the shell scripts. Collection of data in
this manner is useful to characterize system usage over a period of time and
determine peak usage hours.
The commonly used flags of the sar command are provided in Table 3-1.
Table 3-1 Commonly used flags of the sar command
Flag
Description
-A
Without the -P flag, this is equivalent to specifying
-abckmqruvwy. With the -P flag, this is equivalent to specifying
-acmuw.
Chapter 3. CPU and memory performance monitoring tools
45
Flag
Description
-a
Reports use of file access system routines, specifying how
many times per second several of the system file access
routines have been called. When used with the -P flag, the
information is provided for each specified processor;
otherwise, it is provided only system-wide. The following
values are displayed:

dirblk/s
Number of 512-byte blocks read by the directory search
routine to locate a directory entry for a specific file.

iget/s
Number of calls to any of several inode lookup routines
that support multiple file system types. The iget routines
return a pointer to the inode structure of a file or device.

lookuppn/s
Calls to the directory search routine that finds the address
of a v-node, given a path name.
46
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-b
Reports buffer activity for transfers, accesses, and cache
(kernel block buffer cache) hit ratios per second. Access to
most files in AIX Version 3 bypasses kernel block buffering,
and therefore does not generate these statistics. However, if a
program opens a block device or a raw character device for
I/O, traditional access mechanisms are used, making the
generated statistics meaningful. The following values are
displayed:

bread/s, bwrit/s
Reports the number of block I/O operations. These I/Os
are generally performed by the kernel to manage the
block buffer cache area, as discussed in the description
of the lread/s value.

lread/s, lwrit/s
Reports the number of logical I/O requests. When a
logical read or write to a block device is performed, a
logical transfer size of less than a full block size may be
requested. The system accesses the physical device
units of complete blocks and buffers these blocks in the
kernel buffers that have been set aside for this purpose
(the block I/O cache area). This cache area is managed
by the kernel, so that multiple logical reads and writes to
the block device can access previously buffered data from
the cache and require no real I/O to the device.
Application read and write requests to the block device
are reported statistically as logical reads and writes. The
block I/O performed by the kernel to the block device in
management of the cache area is reported as block reads
and block writes.

pread/s, pwrit/s
Reports the number of I/O operations on raw devices.
Requested I/O to raw character devices is not buffered as
it is for block devices. The I/O is performed to the device
directly.

%rcache, %wcache
Reports caching effectiveness (cache hit percentage).
This percentage is calculated as: [(100) x (lreads breads) / (lreads)].
Chapter 3. CPU and memory performance monitoring tools
47
Flag
Description
-c
Reports system calls. When used with the -P flag, the
information is provided for each specified processor;
otherwise, it is provided only system-wide. The following
values are displayed:

exec/s, fork/s
Reports the total number of fork and exec system calls.

sread/s, swrit/s
Reports the total number of read/write system calls.

rchar/s, wchar/s
Reports the total number of characters transferred by
read/write system calls

scall/s
Reports the total number of system calls.
-e hh[:mm[:ss]]
Sets the ending time of the report. The default ending time is
18:00.
-f file
Extracts records from file (created by -o file flag). The default
value of the file parameter is the current daily data file (the
/var/adm/sa/sadd file).
-i seconds
Selects data records at seconds as close as possible to the
number specified by the seconds parameter. Otherwise, the
sar command reports all seconds found in the data file.
-k
Reports kernel process activity. The following values are
displayed:

kexit/s
Reports the number of kernel processes terminating per
second

kproc-ov/s
Reports the number of times kernel processes could not
be created because of enforcement of process threshold
limit

ksched/s
Reports the number of kernel processes assigned to
tasks per second.
48
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-m
Reports message (sending and receiving) and semaphore
(creating, using, or destroying) activities per second. When
used with the -P flag, the information is provided for each
specified processor; otherwise, it is provided only
system-wide. The following values are displayed:

msg/s
Reports the number of IPC message primitives

sema/s
Reports the number of IPC semaphore primitives
-o File
Saves the readings in the file in binary form. Each reading is
in a separate record and each record contains a tag identifying
the time of the reading.
-P
ProcessorIdentifier,
... | ALL
Reports per-processor statistics for the specified processor or
processors. Specifying the ALL keyword reports statistics for
each individual processor, and globally for all processors. Of
the flags that specify the statistics to be reported, only the -a,
-c, -m, -u, and -w flags are meaningful with the -P flag.
-q
Reports queue statistics. The following values are displayed:

runq-sz
Reports the average number of kernel threads in the run
queue

%runocc
Reports the percentage of the time the run queue is
occupied

swpq-sz
Reports the average number of kernel threads waiting to
be paged in

%swpocc
Reports the percentage of the time the swap queue is
occupied
Chapter 3. CPU and memory performance monitoring tools
49
Flag
Description
-r
Reports paging statistics. The following values are displayed:

cycle/s
Reports the number of page replacement cycles per
second.

fault/s
Reports the number of page faults per second. This is not
a count of page faults that generate I/O, because some
page faults can be resolved without I/O.

slots
Reports the number of free pages on the paging spaces.

odio/s
Reports the number of nonpaging disk I/Os per second.
-s hh[:mm[:ss]]
Sets the starting time of the data, causing the sar command to
extract records time-tagged at, or following, the time specified.
The default starting time is 08:00.
-u
Reports per processor or system-wide statistics. When used
with the -P flag, the information is provided for each specified
processor; otherwise, it is provided only system-wide.
Because the -u flag information is expressed as percentages,
the system-wide information is simply the average of each
individual processor's statistics. Also, the I/O wait state is
defined system-wide and not per processor. The following
values are displayed:

%idle
Reports the percentage of time the CPU or CPUs were
idle with no outstanding disk I/O requests.

%sys
Reports the percentage of time the CPU or CPUs spent in
execution at the system (or kernel) level.

%usr
Reports the percentage of time the CPU or CPUs spent in
execution at the user (or application) level.

%wio
Reports the percentage of time the CPU or CPUs were
idle waiting for disk I/O to complete. For system-wide
statistics, this value may be slightly inflated if several
processors are idling at the same time (an unusual
occurrence).
50
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-v
Reports status of the process, kernel-thread, inode, and file
tables. The following values are displayed file-sz, inod-sz,
proc-sz, thrd-sz.
Reports the number of entries in use for each table.
-w
Reports system switching activity. When used with the -P flag,
the information is provided for each specified processor;
otherwise, it is provided only system-wide. The following value
is displayed pswch/s.
Reports the number of context switches per second.
-y
Reports tty device activity per second.

canch/s
Reports tty canonical input queue characters. This field is
always 0 (zero) for AIX Version 4 and higher.

mdmin/s
Reports tty modem interrupts.

outch/s
Reports tty output queue characters.

rawch/s
Reports tty input queue characters.

revin/s
Reports tty receive interrupts.

xmtin/s
Reports tty transmit interrupts.
Note: The sar command:
 The sar command itself can generate a considerable number of reads and
writes, depending on the interval at which it is run. Run the sar statistics
without the workload to understand the sar command's contribution to your
total statistics.
 The sar command reports system unit activity if no other specific content
options are requested.
3.1.4 The sadc command
The sadc command provides a system data collector report.
Chapter 3. CPU and memory performance monitoring tools
51
The syntax for the sadc command is as follows:
sadc [ interval number ] [ outfile ]
It samples system data at a specified interval measured in seconds (interval) a
specified number of times (number). It writes in binary format to the specified file
(outfile) or to the standard output. When both interval and number are not
specified, a dummy record, which is used at system startup to mark the time
when the counter restarts from 0, will be written. The sadc command is intended
to be used as a backend to the sar command.
AIX contains a number of counters that are increased as various system actions
occur. The various system actions include:
 System unit utilization counters
 Buffer usage counters
 Disk and tape I/O activity counters
 TTY device activity counters
 Switching and subroutine counters
 File access counters
 Queue activity counters
 Interprocess communication counters
3.1.5 The sa1 and sa2 commands
The sa1 command is a shell procedure variant of the sadc command and handles
all of the flags and parameters of that command. The sa1 command collects and
stores binary data in the /var/adm/sa/sadd file, where dd is the day of the month.
The syntax for the sa1 command is as follows:
sa1 [ interval number ]
The interval and number parameters specify that the record should be written a
number times at an interval of seconds. If you do not specify these parameters, a
single record is written.
The sa1 command is designed to be started automatically by the cron command.
If the sa1 command is not run daily from the cron command, the sar command
displays a message about the nonexistence of the /usr/lib/sa/sa1 data file.
The sa2 command is a variant shell procedure of the sar command, which writes
a daily report in the /var/adm/sa/sardd file, where dd is the day of the month. The
sa2 command handles all of the flags and parameters of the sar command.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The sa2 command is designed to be run automatically by the cron command and
run concurrently with the sa1 command.
The syntax for the sa2 command is as follows:
sa2
3.2 The vmstat command
The vmstat command reports statistics about kernel threads, virtual memory,
disks, traps, and CPU activity. Reports generated by the vmstat command can
be used to balance system load activity. These system-wide statistics (among all
processors) are calculated as averages for values expressed as percentages,
and as sums otherwise.
The vmstat command syntax is as follows:
vmstat [ -f ] [ -i ] [ -s ] [ PhysicalVolume ] [ interval [ count ] ]
If the vmstat command is invoked without flags, the report contains a summary of
the virtual memory activity since system startup. If the -f flag is specified, the
vmstat command reports the number of forks since system startup. The
PhysicalVolume parameter specifies the name of the physical volume.
An example of the vmstat command without any flags follows:
# vmstat
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 15982 1388
0
0
0
8
22
0 113 281 36 1 0 98 1
Below is an example of the vmstat command with the -f flag:
# vmstat -f
51881 forks
The interval parameter specifies the amount of time in seconds between each
report. The first report contains statistics for the time since system startup.
Subsequent reports contain statistics collected during the interval since the
previous report. If the interval parameter is not specified, the vmstat command
generates a single report and then exits. The count parameter can only be
specified with the interval parameter. If the count parameter is specified, its value
determines the number of reports generated and the frequency data is collected
in seconds. If the interval parameter is specified without the count parameter,
reports are continuously generated. A count parameter of 0 is not allowed.
Chapter 3. CPU and memory performance monitoring tools
53
The following is an example of the vmstat command with the interval and count
parameters:
# vmstat 1 5
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 15982 1388
0
0
0
8
22
0 113 281 36 1 0 98 1
0 0 15982 1387
0
0
0
0
0
0 108 4194 31 2 3 95 0
0 0 15982 1387
0
0
0
0
0
0 109 286 30 0 0 99 0
0 0 15982 1387
0
0
0
0
0
0 108 285 26 0 0 99 0
0 0 15982 1387
0
0
0
0
0
0 111 286 32 0 0 99 0
The kernel maintains statistics for kernel threads, paging, and interrupt activity.
For disks, the average transfer rate is determined by using the active time and
number of transfers information. The percent active time is computed from the
amount of time the drive is busy during the report.
The vmstat command with additional information regarding a specific disk is as
follows:
# vmstat hdisk1
kthr
memory
page
faults
cpu
disk xfer
----- ----------- ------------------------ ------------ ----------- ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa 1 2 3 4
0 0 16273 8385
0
0
0
9
22
0 115 284 39 1 1 98 1 0
In the previous example of a report generated by the vmstat command, the
column headings and their descriptions have the following meaning.
kthr
Kernel thread state changes per second over the
sampling interval.
r
Number of kernel threads placed in run queue
b
Number of kernel threads placed in wait queue
(awaiting resource, awaiting input or output)
Memory
avm
54
Information about the usage of virtual and real memory.
Virtual pages are considered active if they are allocated.
A page is 4096 bytes.
Active virtual pages. When a process executes, space
for working storage is allocated on the paging devices
(backing store). This can be used to calculate the
amount of paging space assigned to executing
processes. The number in the avm field divided by 256
will yield the number of megabytes (MB), system wide,
allocated to page space. The lsps -a command also
provides information on individual paging space. It is
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
recommended that enough paging space be
configured on the system so that the paging space
used does not approach 100 percent. When fewer
than 128 unallocated pages remain on the paging
devices, the system will begin to kill processes to free
some paging space.
fre
Size of the free list. The system maintains a buffer of
memory frames, called the free list, that will be readily
accessible when the VMM needs space. The nominal
size of the free list varies depending on the amount of
real memory installed. On systems with 64 MB of
memory or more, the minimum value (MINFREE) is
120 frames. For systems with less than 64 MB, the
value is two times the number of MB of real memory,
minus 8. For example, a system with 32 MB would
have a MINFREE value of 56 free frames. The
MINFREE and MAXFREE limits can be shown using
the vmtune command.
Note: A large portion of real memory is utilized as a cache for file system data.
It is not unusual for the size of the free list to remain small.
Page
Information about page faults and paging activity. These
are averaged over the interval and given in units per
second. The AIX VMM implements a technique called
Early Allocation of Paging Space. When a page is
allocated in RAM, and it is not a Client (NFS) or a
Persistent (disk file) Storage Page, then it is considered a
Working Storage Page. Working Storage Pages are
commonly an application's stack, data, and any shared
memory segments. So, when a program's stack or data
area is increased, and RAM is accessed, the VMM will
allocate space in RAM and space on the paging device.
This means that even before RAM is exhausted, paging
space is used.
re
Pager input/output list. The number of reclaims per
second. During a page fault, when the page is on the
free list and has not been reassigned, this is
considered a reclaim because no new I/O request has
been initiated. It also includes the pages last
requested by the VMM for which I/O has not been
completed or those prefetched by VMM’s read-ahead
mechanism but hidden from the faulting segment.
Chapter 3. CPU and memory performance monitoring tools
55
pi
Pages paged in from paging space.
po
Pages paged out to paging space.
Note: pi and po values only include Working Storage Pages, not Persistent
Storage Pages.
fr
Pages freed (page replacement).
sr
Pages scanned by page-replacement algorithm.
cy
Clock cycles by page-replacement algorithm.
Faults
Trap and interrupt rate averages per second over the
sampling interval.
in
Device interrupts.
sy
System calls.
cs
Kernel thread context switches.
CPU
Breakdown of percentage usage of CPU time.
us
User time.
sy
System time.
id
CPU idle time.
wa
CPU cycles to determine that the current process is
waiting and there is pending disk input/output.
Disk xfer
Provides the number of transfers per second to the
specified physical volumes that occurred in the sample
interval. The PhysicalVolume parameter can be used to
specify one to four names. Transfer statistics are given for
each specified drive in the order specified. This count
represents requests to the physical device. It does not
imply an amount of data that was read or written. Several
logical requests can be combined into one physical
request.
The vmstat command, used with the -s flag, writes to the standard output the
contents of the sum structure, which contain an absolute count of paging events
since system initialization. The -s option is exclusive of the other vmstat
command options.
The following is an example of the vmstat command using the -s flag:
# vmstat -s
8765020 total address trans. faults
4832918 page ins
56
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
2989263
19
7
0
5417148
12633
15031850
118
6086090
105808
0
0
0
2025516
3031667
3031667
24786000
77240518
0
0
191650677
page outs
paging space page ins
paging space page outs
total reclaims
zero filled pages faults
executable filled pages faults
pages examined by clock
revolutions of the clock hand
pages freed by the clock
backtracks
lock misses
free frame waits
extend XPT waits
pending I/O waits
start I/Os
iodones
cpu context switches
device interrupts
software interrupts
traps
syscalls
A list of all the possible events is provided in the following.
address trans. faults
Incremented for each occurrence of an
address translation page fault. I/O may or may
not be required to resolve the page fault.
Storage protection page faults (lock misses)
are not included in this count.
page ins
Incremented for each page read in by the
virtual memory manager. The count is
incremented for page ins from page space and
file space. Along with the page-out statistic,
this represents the total amount of real I/O
initiated by the virtual memory manager.
page outs
Incremented for each page written out by the
virtual memory manager. The count is
incremented for page-outs to page space and
for page-outs to file space. Along with the
page-in statistic, this represents the total
amount of real I/O initiated by the virtual
memory manager.
paging space page ins
Incremented for VMM-initiated page-ins from
paging space only.
paging space page outs
Incremented for VMM-initiated page-outs to
paging space only.
Chapter 3. CPU and memory performance monitoring tools
57
58
total reclaims
Incremented when an address translation fault
can be satisfied without initiating a new I/O
request. This can occur if the page has been
previously requested by VMM, but the I/O has
not yet completed; or if the page was
pre-fetched by VMM's read-ahead algorithm,
but was hidden from the faulting segment; or if
the page has been put on the free list and has
not yet been reused.
zero filled pages faults
Incremented if the page fault is to working
storage and can be satisfied by assigning a
frame and zero-filling it.
executable filled pages faults
Incremented for each instruction page fault.
pages examined by clock
VMM uses a clock-algorithm to implement a
pseudo least recently used (LRU) page
replacement scheme. Pages are aged by
being examined by the clock. This count is
incremented for each page examined by the
clock.
revolutions of the clock hand
Incremented for each VMM clock revolution
(that is, after each complete scan of memory).
pages freed by the clock
Incremented for each page the clock algorithm
selects to free from real memory.
backtracks
Incremented for each page fault that occurs
while resolving a previous page fault. (The
new page fault must be resolved first and then
initial page faults can be backtracked.)
lock misses
VMM enforces locks for concurrency by
removing address ability to a page. A page
fault can occur due to a lock miss, and this
count is incremented for each such
occurrence.
free frame waits
Incremented each time a process is waited by
VMM while free frames are gathered.
extend XPT waits
Incremented each time a process is waited by
VMM due to a commit in progress for the
segment being accessed.
pending I/O waits
Incremented each time a process is waited by
VMM for a page-in I/O to complete.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
start I/Os
Incremented for each read or write I/O request
initiated by VMM.
iodones
Incremented at the completion of each VMM
I/O request.
CPU context switches
Incremented for each CPU context switch
(dispatch of a new process).
device interrupts
Incremented for each hardware interrupt.
software interrupts
Incremented for each software interrupt. A
software interrupt is a machine instruction
similar to a hardware interrupt that saves
some state and branches to a service routine.
System calls are implemented with software
interrupt instructions that branch to the system
call handler routine.
traps
Unused by the AIX operating system.
syscalls
Incremented for each system call.
In the following examples, an idle system will be shown, and then load will be put
on to the system; the resultant output will be analyzed to investigate potential
problems.
The following is the output of the vmstat command without any load:
# vmstat 1 5
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 16057 1291
0
0
0
8
22
0 113 281 36 1 0 98 1
0 0 16057 1290
0
0
0
0
0
0 108 472 25 0 0 99 0
0 0 16057 1290
0
0
0
0
0
0 109 282 32 0 0 99 0
0 0 16057 1290
0
0
0
0
0
0 109 285 26 0 0 99 0
0 0 16057 1290
0
0
0
0
0
0 108 282 29 0 0 99 0
The first output line gives the average since system boot and can be left out
when calculating system load. This is the same as running the vmstat command
without any flags.
For the purpose of this exercise, the output of the vmtune command is as follows:
# /usr/samples/kernel/vmtune
vmtune: current values:
-p
-P
-r
-R
minperm maxperm minpgahead maxpgahead
26007
104028
2
8
-f
minfree
120
-F
maxfree
128
-N
-W
pd_npages maxrandwrt
524288
0
Chapter 3. CPU and memory performance monitoring tools
59
-M
-w
-k
-c
-b
-B
-u
-l
maxpin npswarn npskill numclust numfsbufs hd_pbuf_cnt lvm_bufcnt lrubucket
defps
104851
4096
1024
1
93
80
9
131072
-s
sync_release_ilock
0
-n
nokillroot
0
-S
v_pinshm
0
number of valid memory pages = 131063
maximum pinable=80.0% of real memory
number of file memory pages = 101629
-d
1
-h
strict_maxperm
0
maxperm=79.4% of real memory
minperm=19.8% of real memory
numperm=77.5% of real memory
The vmstat command, with only an interval parameter and count parameter, is
as follows:
# vmstat 1 15
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 16299 1749
0
0
0
8
21
0 113 281 36 1 0 98 1
1 1 16299 1529
0
0
0
0
0
0 301 8707 382 52 13 0 35
1 1 16299 1398
0
0
0
0
0
0 185 6557 238 91 8 0 1
1 1 16299 1227
0
0
0
0
0
0 225 6705 257 85 15 0 0
1 0 16299 1049
0
0
0
0
0
0 246 6587 334 71 10 0 19
1 1 16299
861
0
0
0
0
0
0 250 9051 317 72 19 0 9
0 1 16265
653
0
0
0
0
0
0 342 10304 516 37 21 0 43
4 0 16284
121
0
0
0 16
35
0 253 2432 375 36 6 43 15
0 0 16284
120
0
0
0 432 1066
0 265 302 246 31 4 54 11
1 0 16284
121
0
0
0 160 389
0 221 1184 239 8 5 77 10
0 1 16284
120
0
0
0 576 1447
0 394 2377 525 28 9 39 24
0 0 16284
122
0
0
0 232 480
0 277 1185 346 21 5 63 11
0 0 16284
122
0
0
0 384 1630
0 326 1081 400 16 12 51 21
0 0 16284
126
0
0
0 336 784
0 284 742 326 20 3 59 18
0 1 16284
126
0
0
0 761 1615
0 336 1032 420 36 4 48 12
As listed, kthr (kernel thread), r (runnable threads), and b (waiting threads)
outputs stayed relatively constant and low. The r thread should be less than 5
under a stable workload. This b value should usually be near 0.
In the memory column, the avm (average paging space memory) stayed
relatively stable but the fre (free memory frames) value dropped from 1749 to its
lowest of 120. If the fre value had dropped below 120 for an extended period of
time, this system would be continuously paging in and out, which would lead to
system performance problems.
For the page heading, the re, pi, po, and cy values remained relatively constant.
The fr and sr rates, however, increased substantially. The pi rate should not go
above five; however if a page-in occurs, then there must have been a previous
60
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
page-out for that page. It is also likely in a memory-constrained environment that
each page-in will force a different page to be stolen and, therefore, paged out. If
the system is reading in a significant number of persistent pages, you may see
an increase in po without corresponding increases in pi. This situation does not
necessarily indicate thrashing, but may warrant investigation into data access
patterns of the applications. The fr column represents the number of pages freed
and the sr column represents the number of pages scanned by the page
placement algorithm. With stable, unfragmented memory, the scan rate and free
rate may be nearly equal. On systems with multiple processes using many
different pages, the pages are more volatile and disjointed. In this scenario, the
scan rate may greatly exceed the free rate.
For the faults heading, the in, sy, and cs values fluctuated at various intervals.
There is no steadfast limit to these, as the overhead is minimal, and it is difficult
to say what is excessive. The only thing to remember is that the in value will
always be higher than 100.
For the cpu heading, the us, sy, id, and wa values also fluctuated dramatically.
The output is in percent of CPU utilization. The us output is the amount of time
spent by a process executing functions without having to use the system (kernel)
mode. The sy time details the amount of time a process spends utilizing system
(kernel) resources. Optimum use would have the CPU working 100 percent of
the time. This holds true in the case of a single-user system with no need to
share the CPU. Generally, if us + sy time is below 90 percent, a single-user
system is not considered CPU constrained. However, if us + sy time on a
multi-user system exceeds 80 percent, the processes may spend time waiting in
the run queue. Response time and throughput might suffer. The id output is the
CPU idle time. The wa output is idle time with pending local disk I/O. A wa value
over 40 percent could indicate that the disk subsystem may not be balanced
properly, or it may be the result of a disk-intensive workload. The four values
added together will give a CPU utilization of 100 percent.
3.3 The ps command
In this section, the following topics are covered:
 Use of the ps command in CPU usage study
 Use of the ps command in memory usage study
The ps command determines which processes are running and the resources
they use.
Chapter 3. CPU and memory performance monitoring tools
61
3.3.1 Use of the ps command in a CPU usage study
Three of the possible ps command output columns report CPU usage, each in a
different way, as shown in Table 3-2. These columns will be the topic of
discussion in the sections that follow.
Table 3-2 CPU-related ps output
Column
Value
C
Recent used CPU time for process.
TIME
Total CPU time used by the process since it started.
%CPU
Total CPU time used by the process since it started, divided by the
elapsed time since the process started. This is a measure of the
dependence of the program on CPU.
The C column
The C column can be generated by the -l flag and the -f flag. In this column, the
CPU utilization of processes or threads is reported. The value is incremented
each time the system clock ticks and the process or thread is found to be
running. Therefore, it also can be said to be a process penalty for recent CPU
usage. The value is decayed by the scheduler by dividing it by 2 once per second
when the process is not using CPU. Large values indicate a CPU-intensive
process and result in lower process priority, while small values indicate an I/O
intensive process and result in a more favorable priority. In the following example,
the tctestprog program is a CPU-intensive program.
Another aspect of the ps command is the formatted output. The following
formatting sorts the output according to the third column with the largest value at
the top, and shows only five lines of the total output:
# ps -ef
UID
root
root
root
root
| sort +3 -r |head -n 5
PID PPID
C
STIME
TTY TIME CMD
22656 27028 101 15:18:31 pts/11 7:43 ./tctestprog
14718 24618
5 15:26:15 pts/17 0:00 ps -ef
4170
1
3
Jun 15
- 12:00 /usr/sbin/syncd 60
21442 24618
2 15:26:15 pts/17 0:00 sort +3 -r
From the previous example, you can determine that tctestprog is the process
using the most CPU, due to the C value of 101.
The following vmstat output shows that the CPU is used about 25 percent by usr
processes:
# vmstat 2 3
kthr
memory
62
page
faults
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
cpu
----- ----------- ------------------------ ------------ ----------r b avm
fre
re pi po fr sr cy in sy
cs us sy id
0 0 26468 51691 0 0 0 0 0 0 100 91
6
47 0 53
1 1 26468 51691 0 0 0 0 0 0 415 35918 237 26 2 71
1 1 26468 51691 0 0 0 0 0 0 405 70
26 25 0 75
wa
0
0
0
The TIME column
The ps command output column TIME is generated with all flags, and it shows
the total execution time for the process. This calculation does not take into
account when the process was started, as seen in the following output. The
same test program is used again, and even though the C column shows that the
process gets a lot of CPU time, it is not the process with the largest value in the
TIME column:
# ps -ef
UID
root
root
root
root
| sort +3 -r |head -n 5
PID PPID
C
STIME
18802 27028 120 15:40:28
9298 24618
3 15:41:38
15782 24618
2 15:41:38
24618 26172
2
Jun 21
TTY
pts/11
pts/17
pts/17
pts/17
TIME CMD
1:10 ./tctestprog
0:00 ps -ef
0:00 head -n 5
0:03 ksh
# ps -e |head -n 1 ; ps -e|egrep -v "TIME|0:"|sort +2b -3 -n -r|head -n 10
PID
TTY TIME CMD
4170
- 12:01 syncd
4460
- 2:07 X
3398
- 1:48 dtsession
18802 pts/11 1:14 tctestprog
The syncd, X, and dtsession are all processes that have been active since IPL;
that is why they have accumulated more total TIME than the test program.
The %CPU column
The %CPU column of the ps command output, generated by the -u or the -v
flags, shows the percentage of time the process has used the CPU since the
process started. The value is computed by dividing the time the process uses the
CPU by the elapsed time of the process. In a multi-processor environment, the
value is further divided by the number of available CPUs, because several
threads in the same process can run on different CPUs at the same time.
Because the time base over which this data is computed varies, the sum of all
%CPU fields can exceed 100 percent. In the example below, there are two ways
to sort the extracted output from a system. The first example includes kprocs, for
example, PID 516, which is a wait process. The other, more complex command
syntax, excludes such kprocs:
# ps auxwww |head -n 5
USER
PID %CPU %MEM
SZ RSS
root
18802 25.0 1.0 4140 4160
TTY STAT
STIME
pts/11 A
15:40:28
TIME COMMAND
5:44 ./tctestprog
Chapter 3. CPU and memory performance monitoring tools
63
root
root
root
516 25.0
774 20.6
1290 5.9
5.0
5.0
5.0
8 15136
8 15136
8 15136
# ps gu|head -n1; ps gu|egrep
USER
PID %CPU %MEM
SZ
root
18802 25.0 1.0 4140
imnadm
12900 0.0 0.0 264
root
0 0.0 5.0
12
root
1 0.0 0.0 692
root
3398 0.0 1.0 1692
- A
- A
- A
Jun 15 17246:34 kproc
Jun 15 14210:30 kproc
Jun 15 4077:38 kproc
-v "CPU|kproc"|sort +2b -3 -n -r |head -n 5
RSS
TTY STAT
STIME TIME COMMAND
4160 pts/11 A
15:40:28 7:11 ./tctestprog
332
- A
Jun 15 0:00 /usr/IMNSearch/ht
15140
- A
Jun 15 4:11 swapper
764
- A
Jun 15 0:28 /etc/init
2032
- A Jun 15 1:48 /usr/dt/bin/dtses
From the output, you can determine that the test program, tctestprog, has used
about 25 percent of the available CPU resources since the process started.
The commonly used flags of the ps command are provided in Table 3-3.
Table 3-3 Commonly used flags of the ps command
64
Flag
Description
-A
Writes to standard output information about all processes.
-a
Writes to standard output information about all processes, except the
session leaders and processes not associated with a terminal.
-c Clist
Displays only information about processes assigned to the workload
management classes listed in the Clist variable. The Clist variable is
either a comma-separated list of class names or a list of class names
enclosed in double quotation marks (" "), which is separated from one
another by a comma or by one or more spaces, or both.
-d
Writes information to standard output about all processes except the
session leaders.
-e
Writes information to standard output about all processes except
kernel processes.
-F format
Same as -o format.
-f
Generates a full listing.
-k
Lists kernel processes.
-l
Generates a long listing. See also the -l flag.
-m
Lists kernel threads as well as processes. Output lines for processes
are followed by an additional output line for each kernel thread.
-o format
Displays information in the format specified by the format variable.
a
Displays information about all processes with terminals.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
e
Displays the environment as well as the parameters to the command
up to a limit of 80 characters.
g
Displays all processes.
3.3.2 Use of the ps command in a memory usage study
The ps command can also provide useful information on memory usage. The
most useful output is presented in Table 3-4 and discussed in the following
sections.
Table 3-4 Memory-related ps output
Column
Value
SIZE
The virtual size of the data section of the process in 1 KB units
RSS
The real-memory size of the process in 1 KB units
%MEM
The percentage of real memory used by this process
The SIZE column
The v flag generates the SIZE column. This is the virtual size (in the paging
space), in kilobytes, of the data section of the process (displayed as SZ by other
flags). This value is equal to the number of working segment pages of the
process that have been touched times four. If several working segment pages
are currently paged out, this number is larger than the amount of real memory
being used. SIZE includes pages in the private segment and the shared-library
data segment of the process, as in the following example:
# ps av |sort
PID
TTY
25298 pts/10
13160
lft0
27028 pts/11
24618 pts/17
+5 -r
STAT
A
A
A
A
|head -n 5
TIME PGIN SIZE
0:00
0 2924
0:00
17
368
0:00
90
292
0:04 318
292
RSS
12
72
416
408
LIM
32768
32768
32768
32768
TSIZ
TRS %CPU %MEM COMMAND
159
0 0.0 0.0 smitty
40 60 0.0 0.0/usr/sbin
198
232 0.0 1.0 ksh
198
232 0.0 1.0 ksh
The RSS column
The v flag also produces the RSS column, as shown in the previous example.
This is the real-memory (resident set) size in kilobytes of the process. This
number is equal to the sum of the number of working segment and code segment
pages in memory times four. Remember that code segment pages are shared
among all of the currently running instances of the program. If 26 ksh processes
are running, only one copy of any given page of the ksh executable program
would be in memory, but the ps command would report that code segment size
as part of the RSS of each instance of the ksh program.
Chapter 3. CPU and memory performance monitoring tools
65
If you want to sort on the sixth column, you receive the output sorted by the RSS
column, as shown in the following example:
# ps av |sort +6 -r |head -n 5
PID
TTY STAT TIME PGIN SIZE
RSS
21720 pts/1 A
0:00
1
288
568
27028 pts/11 A
0:00
90
292
416
24618 pts/17 A
0:04 318
292
408
15698 pts/1 A
0:00
0
196
292
LIM TSIZ
TRS %CPU %MEM COMMAND
32768
198
232 0.0 1.0 ksh
32768
198
232 0.0 1.0 ksh
32768
198
232 0.0 1.0 ksh
32768
52
60 0.0 0.0 ps av
The %MEM column
The %MEM column is generated by the u and the v flags. This is calculated as
the sum of the number of working segment and code segment pages in memory
times four (that is, the RSS value), divided by the size of the real memory of the
machine in KB, times 100, rounded to the nearest full percentage point. This
value attempts to convey the percentage of real memory being used by the
process. Unfortunately, it tends to exaggerate the cost of a process that is
sharing program text with other processes, such as with RSS. The rounding to
the nearest percentage point causes all of the processes in the system that have
RSS values under .005 times real memory size to have a %MEM of 0.0.
The following is an example of the ps %MEM column:
# ps au |head -n 1; ps au |egrep -v "RSS"|sort +3 -r |head -n 5
USER
PID %CPU %MEM
SZ RSS
TTY STAT
STIME TIME COMMAND
root
22750 0.0 21.0 20752 20812 pts/11 A 17:55:51 0:00./tctestprog2 root
21720 0.0 1.0 484 568 pts/1 A
17:16:14 0:00 ksh
root
25298 0.0 0.0 3080
12 pts/10 A
Jun 16 0:00 smitty
root
27028 0.0 0.0 488 416 pts/11 A
14:53:27 0:00 ksh
root
24618 0.0 0.0 488 408 pts/17 A
Jun 21 0:04 ksh
You can combine all of these columns into one output by using the gv flags. For
example:
# ps gv|head -n 1; ps gv|egrep -v "RSS" |
PID
TTY STAT TIME PGIN SIZE RSS
LIM
15674 pts/11 A
0:01
0
36108 36172
22742 pts/11 A
0:00
0
20748 20812
10256 pts/1 A
0:00
0
15628 15692
2064
- A
2:13
5
64 6448
1806
- A
0:20
0
16 6408
sort +6b -7 -n -r |head -n 5
TSIZ TRS %CPU %MEM COMMAND
32768
5
24 0.6 24.0 ./tctestp
32768 5
24 0.0 14.0 ./backups
32768 5
24 0.0 11.0 ./tctestp
xx
0 6392 0.0 4.0 kproc
xx
0 6392 0.0 4.0 kproc
In the following list, additional columns in the previous examples are explained:
PGIN
66
The number of page-ins caused by page faults. Since all
I/O operations are classified as page faults by the ps
command, this is a measure of I/O volume.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
TSIZ
The size of the text (shared-program) image. This is the
size of the text section of the executable file. Pages of the
text section of the executable program are only brought
into memory when they are touched, that is, branched to
or loaded from. This number represents only an upper
bound on the amount of text that could be loaded. The
TSIZ value does not reflect actual memory usage. This
TSIZ value can also be seen by executing the dump -ov
command against an executable program (for example,
dump -ov /usr/bin/ls).
TRS
The size of the resident set (real memory) of text. This is
the number of code segment pages multiplied by four.
This number exaggerates the memory used for programs
where multiple instances are running. The TRS value can
be higher than the TSIZ value because other pages may
be included in the code segment, such as the XCOFF
header and the loader section.
3.4 The tprof command
In this section the following topics are discussed:
 The use of tprof to study general CPU performance
 The use of tprof on a user program
3.4.1 Using the tprof general report
In the AIX operating system, an interrupt occurs periodically to allow a
housekeeping kernel routine to run. This occurs 100 times per second. When the
tprof command is invoked, it counts every such kernel interrupt as a tick. This
kernel routine records the process ID and the address of the instruction
executing when the interrupt occurs, for use by the tprof command. The tprof
command also records whether the process counter is in the kernel address
space, user address space, or shared library address space.
A summary ASCII report with the suffix .all is always produced. If no program is
specified, the report is named __prof.all. If a program is specified, the report is
named __program.all. This report contains an estimate of the amount of CPU
time spent in each process that was executing while the tprof program was
monitoring the system. It also contains an estimate of the amount of CPU time
spent in each of the three address spaces and the amount of time the CPU was
idle.
Chapter 3. CPU and memory performance monitoring tools
67
The tprof command uses the AIX Kernel trace facility. Only one user can use
the AIX trace facility at a time. Thus, only one tprof command can be active in
the system at a time.
The files containing the reports are left in the working directory. All files created
by the tprof command are prefixed by ___ (two underscores).
In the following example, a generic report is generated:
# tprof -x sleep 30
Starting Trace now
Starting sleep 30
Wed Jun 28 14:58:58 2000
System: AIX server3 Node: 4 Machine: 000BC6DD4C00
Trace is done now
30.907 secs in measured interval
* Samples from __trc_rpt2
* Reached second section of __trc_rpt2
In this case, the sleep 30 parameter directs the tprof command to run for 30
seconds.
The Total column in the __prof.all is useful. The first section indicates the use of
ticks on a per process basis.
Process
=======
wait
tctestprg
tctestprg
wait
wait
swapper
tprof
trace
syncd
tprof
gil
gil
trace
sh
sleep
=======
Total
PID
===
516
14746
13730
1032
1290
0
14156
16000
3158
5236
2064
2064
15536
14002
14002
===
TID
Total
===
=====
517
3237
13783
3207
17293
3195
1033
3105
1291
138
3
10
5443
6
14269
3
4735
2
16061
2
2839
1
3097
1
14847
1
16905
1
16905
1
===
=====
12910
Kernel User
Shared
Other
====== ====
======
=====
3237 0
0
0
1
3206
0
0
0
3195
0
0
3105 0
0
138
0
0
0
7
3
0
0
3
3
0
0
3
0
0
0
2
0
0
0
2
0
0
0
1
0
0
0
1
0
0
1
0
0
0
1
0
0
0
1
0
0
0
======
====
======
=====
6503
6407
0
0
Since each tick is 1/100 second, 30 seconds requires a total of 3000 ticks.
However, when looking at the output, there are over 12000 total ticks. The result
68
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
is dependent on the hardware, in this case a four-way F50, so the available ticks
are calculated in the following way:
Time (in seconds) x number of available CPUs x 100
In the previous output, you can determine that both tctestprg processes use
about 3200 ticks, approximately 25 percent of the total available ticks. This is
confirmed with the following ps auxwww output:
# ps auxwww
USER
PID %CPU %MEM
root
14020 25.0 0.0
root
12280 25.0 0.0
SZ
300
300
RSS
320
320
TTY STAT
STIME TIME COMMAND
pts/1 A
15:23:55 16:45 ./tctestprg
pts/1 A
15:23:57 16:43 ./tctestprg
In the second section of the general report of the tproc command, the total
amount of ticks used by a specified type of process is noted. In this section, the
total ticks used by a process type are in the Total column, and the number of
processes representing that type can be seen in the FREQ column.
Process
=======
wait
tctestprg
swapper
tprof
trace
gil
syncd
sh
sleep
=======
Total
FREQ
===
3
2
1
2
2
2
1
1
1
===
15
Total
=====
6480
6402
10
8
4
2
2
1
1
=====
12910
Kernel
======
6480
1
7
5
4
2
2
1
1
======
6503
User
====
0
6401
3
3
0
0
0
0
0
====
6407
Shared
======
0
0
0
0
0
0
0
0
0
======
0
Other
=====
0
0
0
0
0
0
0
0
0
=====
0
3.4.2 Using tprof on a program
The tprof command is also a useful tool for C, C++, or FORTRAN programs that
might be CPU bound. It identifies sections of a program that are most heavily
using the CPU. The tprof command executes a program and then produces a
set of files containing reports. The reports are divided down to subroutine level.
The following example is a basic one; there are many more possibilities outside
the scope of this document:
# tprof ./tctestprg
Starting Trace now
Starting ./tctestprg
Wed Jun 28 15:57:35 2000
System: AIX server3 Node: 4 Machine: 000BC6DD4C00
Trace is done now
Chapter 3. CPU and memory performance monitoring tools
69
23.258 secs in measured interval
* Samples from __trc_rpt2
* Reached second section of __trc_rpt2
(The tctestprg process was manually killed)
The output file is named __tctestprg.all, and the output is restricted to the
process provided as an argument to the command. The first section is the same
as shown in a general report. However, it only reflects a single process.
# more __tctestprg.all
Process
PID
TID
=======
===
===
./tctestprg 16276
16081
=======
===
===
Total
Total
Kernel
=====
======
2156
0
=====
======
2156
0
User
Shared
Other
====
======
=====
2156
0
0
====
======
=====
2156
0
0
The second section is a trivial report on the single process.
Process
FREQ
=======
===
./tctestprg 1
=======
===
Total
1
Total
=====
2156
=====
2156
Kernel
======
0
======
0
User
====
2156
====
2156
Shared
======
0
======
0
Other
=====
0
=====
0
The third section provides information about the subroutines used in the
specified process providing information about areas that require tuning.
Total Ticks For ./tctestprg (USER) =
Subroutine
Ticks %
=============
===== ====
.main
1368 14.5
.casework
788 8.4
2156
Source
========
case.c
case.c
Address Bytes
======== ======
10000318 4c
10000364 54
3.5 The svmon command
The svmon command is used to display information regarding the current memory
state. Although it is a complicated command, you should understand what it can
do to assist you in performance monitoring.
The svmon command generates seven types of reports:
 Global
 User
 Process
 Segment
 Detailed segment
70
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 Command
 Workload management class
To run each of these reports, a report indicator flag needs to be used.
With the exception of the svmon -G and svmon -D reports, the other report options
use the same flags with a similar use. In the following sections, an example of
the command and the output generated is provided. This is not an exhaustive list
of functions; rather, it is a short demonstration of the versatility of the svmon
command. For an explanation of the flags, see 3.5.8, “The svmon command
flags” on page 90.
3.5.1 The svmon global report
The global report is generated when the -G flag is specified.
The svmon -G command has the following syntax:
svmon -G [ -i interval [ NumIntervals]] [ -z ]
Running the svmon -G global report command generates the following output:
# svmon -G
memory
pg space
pin
in use
size
131063
131072
inuse
119922
305
free
11141
work
6816
21791
pers
0
98131
clnt
0
0
pin
6807
virtual
15924
The svmon -G command with an interval and the number of intervals, and
providing the -z flag to obtain the maximum memory allocated, provides the
following output:
# svmon -G -i1 5 -z
size
131063
131072
inuse
125037
305
free
6026
pin
in use
work
6820
21950
pers
0
103087
clnt
0
0
memory
size
131063
inuse
125847
free
5216
memory
pg space
pin
6811
virtual
15948
pin
6811
virtual
15949
Chapter 3. CPU and memory performance monitoring tools
71
pg space
pin
in use
memory
pg space
pin
in use
memory
pg space
pin
in use
memory
pg space
pin
in use
131072
305
work
6820
21954
pers
0
103893
clnt
0
0
size
131063
131072
inuse
126769
305
free
4294
work
6820
21954
pers
0
104815
clnt
0
0
size
131063
131072
inuse
127890
305
free
3173
work
6820
21954
pers
0
105936
clnt
0
0
size
131063
131072
inuse
129092
305
free
1971
work
6820
21954
pers
0
107138
clnt
0
0
pin
6811
virtual
15949
pin
6811
virtual
15949
pin
6811
virtual
15949
Maximum memory allocated = 432
In the previous example, the headings have the following meanings:
memory
72
Specifies statistics describing the use of real memory,
including:
size
Number of real memory frames (size of real memory)
inuse
Number of frames containing pages
free
Number of frames free
pin
Number of frames containing pinned pages
virtual
Number of pages allocated in the system virtual space
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
stolen
pg space
Number of frames stolen by rmss (Reduced-Memory
System Simulator; see 3.6, “The rmss command” on
page 92, for more information) and made unusable by
the VMM
Specifies statistics describing the use of paging space.
This data is reported only if the -r flag is not used.
size
Size of paging space
inuse
Number of paging space pages in use
pin
Specifies statistics on the subset of real memory
containing pinned pages, including:
work
Number of frames containing pinned pages from
working segments
pers
Number of frames containing pinned pages from
persistent segments
clnt
Number of frames containing pinned pages from client
segments
in use
Specifies statistics on the subset of real memory in use,
including:
work
Number of frames containing pages from working
segments
pers
Number of frames containing pages from persistent
segments
clnt
Number of frames containing pages from client
segments
3.5.2 The svmon user report
The user report is printed when the -U flag is specified.
The svmon -U command has the following syntax:
svmon -U [ lognm1...lognmN] [ -n | -s ] [ -w | -f | -c ] [ -t count ]
[ -u | -p | -g | -v ] [ -i interval [ NumIntervals]] [ -l ] [ -d ] [ -z ]
[ -m ]
The svmon -U without any options produces output similar to the following:
# svmon -U
===============================================================================
User root
Inuse
Pin
Pgsp Virtual
18447
1327
175
7899
Chapter 3. CPU and memory performance monitoring tools
73
...............................................................................
SYSTEM segments
Inuse
Pin
Pgsp Virtual
3816
1269
175
3535
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
9352
220
7a0f
502a
-
work
work
work
work
Inuse
3792
12
6
4
2
Pin Pgsp Virtual Addr Range
1265 175 3511
0..32767 :
1
1
1
1
0
0
0
0
12
6
4
2
0..49746
0..49746
0..49746
0..49746
...............................................................................
EXCLUSIVE segments
Inuse
Pin
Pgsp Virtual
12551
58
0
3891
Vsid
Esid Type Description
Inuse
Pin Pgsp Virtual Addr Range
7162
- pers /dev/lv00:17
6625
0
0..100987
...
2b65
- pers /dev/hd4:4294
0
0
1369
- pers /dev/hd3:32
0
0
1b63
1 pers code,/dev/hd2:4536
0
0
0..21
5b4b
1 pers code,/dev/hd2:10545
0
0
0..1
1b43
- pers /dev/hd2:32545
0
0
0..0
e6ff
- pers /dev/hd4:732
0
0
3326
1 pers code,/dev/hd2:10553
0
0
0..4
2ee6
- pers /dev/hd2:14469
0
0
ea9d
- pers /dev/hd2:39225
0
0
0..4
d67b
- pers /dev/hd2:32715
0
0
0..0
5668
- pers /dev/hd2:98694
0
0
0..0
466a
1 pers code,/dev/hd2:98696
0
0
0..4
d21a
1 pers code,/dev/hd2:10679
0
0
0..1
a41
- pers /dev/hd2:32224
0
0
0..1
aa15
1 pers code,/dev/hd2:10673
0
0
0..0
f1fe
- pers /dev/hd2:10310
0
0
0..2
e9fd
- pers /dev/hd2:10309
0
0
0..14
c9f9
- pers /dev/hd2:32705
0
0
0..3
b9f7
1 pers code,/dev/hd2:10734
0
0
0..15
a1f4
1 pers code,/dev/hd2:10765
0
0
0..10
3a07
1 pers code,/dev/hd2:10684
0
0
0..7
2a05
1 pers code,/dev/hd2:10718
0
0
0..170
59eb
- pers /dev/hd2:32701
0
0
0..9
e9bd
1 pers code,/dev/hd2:4123
0
0
0..128
...
===============================================================================
User guest
Inuse
Pin
Pgsp Virtual
0
0
0
0
74
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
===============================================================================
User nobody
Inuse
Pin
Pgsp Virtual
0
0
0
0
===============================================================================
User lpd
Inuse
Pin
Pgsp Virtual
0
0
0
0
===============================================================================
User nuucp
Inuse
Pin
Pgsp Virtual
0
0
0
0
===============================================================================
User ipsec
Inuse
Pin
Pgsp Virtual
0
0
0
0
===============================================================================
User netinst
Inuse
Pin
Pgsp Virtual
0
0
0
0
To check a particular users’ utilization, as well as the total memory allocated, use
the following command:
# svmon -U root -z
===============================================================================
User root
Inuse
Pin
Pgsp Virtual
10980
1322
175
7913
...............................................................................
SYSTEM segments
Inuse
Pin
Pgsp Virtual
3816
1269
175
3535
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
9352
220
7a0f
502a
-
work
work
work
work
Inuse
3792
12
6
4
2
Pin Pgsp Virtual Addr Range
1265 175 3511
0..32767 :
1
1
1
1
0
0
0
0
12
6
4
2
0..49746
0..49746
0..49746
0..49746
...............................................................................
EXCLUSIVE segments
Inuse
Pin
Pgsp Virtual
5024
53
0
3905
Vsid
1be3
...
Esid Type Description
2 work process private
Inuse
580
Pin Pgsp Virtual Addr Range
8
0
579
0..675 :
Chapter 3. CPU and memory performance monitoring tools
75
d9fb
c9f9
a1f4
3a07
2a05
d9bb
c955
4168
2965
694d
514a
30a6
4088
dbfb
- pers /dev/hd9var:86
- pers /dev/hd2:32705
1 pers code,/dev/hd2:10765
1 pers code,/dev/hd2:10684
1 pers code,/dev/hd2:10718
1 pers code,/dev/hd2:4379
- pers /dev/hd3:33
- pers /dev/hd2:20485
- pers /dev/hd2:20486
- pers /dev/hd9var:2079
- pers /dev/hd9var:2078
- pers /dev/hd9var:2048
- pers /dev/hd2:4098
- pers /dev/hd3:21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-
-
0..0
0..3
0..10
0..7
0..170
0..20
0..5
0..0
0..7
0..0
0..0
0..0
0..1
...............................................................................
SHARED segments
Inuse
Pin
Pgsp Virtual
2140
0
0
473
Vsid
Esid Type Description
8811
d work shared library text
e03c
1 pers code,/dev/hd2:4204
2865
- pers /dev/hd2:32343
Maximum memory allocated = 21473
Inuse
2080
58
2
Pin Pgsp Virtual Addr Range
0
0
473
0..65535
0
0..58
0
0..1
The headings have the following meaning:
User
Indicates the user name
Inuse
Indicates the total number of pages in real memory in
segments that are used by the user
Pin
Indicates the total number of pages pinned in segments
that are used by the user
Pgsp
Indicates the total number of pages reserved or used on
paging space by segments that are used by the user
Virtual
Indicates the total number of pages allocated in the
process virtual space
Once the column heading is displayed, svmon displays (if the -d flag is specified)
information about all the processes run by the specified login user name. It only
contains the column heading of the processes, as described in the process
report.
Then svmon displays information about the segments used by those processes.
76
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
This set of segments is separated into three categories:
1. The segments that are flagged as system segments that are shared by all
processes
2. The segments that are only used by the set of processes
3. The segments that are shared between several users
If the -l flag is specified, then for each segment in the last category, the list of
process identifiers that use the segment is displayed. The login user name that
executes the process identifier is also displayed.
3.5.3 The svmon process report
The process report is generated when the -P flag is specified.
The svmon -P command has the following syntax:
svmon [-P [pid1...pidn] [ -u | -p | -g | -v ] [ -n | -s ] [ -w | -f | -c]
[ -t count ] [ -i interval [ NumIntervals ] ] [ -l ] [ -z ] [ -m ] ]
The svmon -P command process report has output similar to the following:
# svmon -P | pg
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
11126 backbyname
32698
1266
175
4114
N
N
Vsid
7162
0
Esid Type Description
- pers /dev/lv00:17
0 work kernel seg
65475..65535
8811
c373
4823
d work shared library text
- pers /dev/hd3:2061
2 work process private
65310..65535
2969
cdb7
6d28
5920
f
3
1
-
work
pers
pers
pers
shared library data
shmat/mmap,/dev/hd2:
code,/dev/hd2:10334
/dev/hd2:32166
Inuse
26650
3790
Pin Pgsp Virtual Addr Range
0
0..100362
1265 175 3509
0..32767 :
2030
134
48
0
0
1
0
0
540
48
22
16
7
1
0
0
0
0
0
-
17
-
0..65535
0..133
0..47 :
0..749
0..16
0..6
0..0
-----------------------------------------------------------------------------...
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
3452 telnetd
6001
1266
175
4214
N
N
Chapter 3. CPU and memory performance monitoring tools
77
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
8811
3f24
d work shared library text
2 work process private
65306..65535
fa3f
d67b
3406
9c13
f
3
1
work
pers
work
pers
shared library data
/dev/hd2:32715
shmat/mmap
code,/dev/hd2:10763
Inuse
3790
Pin Pgsp Virtual Addr Range
1265 175 3509
0..32767 :
2030
106
0
1
0
0
540
106
73
1
1
0
0
0
0
0
0
0
-
58
1
-
0..65535
0..96 :
0..640
0..0
0..0
0..101
------------------------------------------------------------------------------...
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
6968 rtcmd
3794
1266
175
3513
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
3790
Pin Pgsp Virtual Addr Range
1265 175 3509
0..32767 :
65475..65535
6a0d
2 work process private
4
1
0
4
65314..65535
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
516 wait
3792
1266
175
3511
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
3790
Pin Pgsp Virtual Addr Range
1265 175 3509
0..32767 :
65475..65535
8010
2 work process private
2
1
0
2
65339..65535
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
0
3
1
0
3
N
N
Vsid
Esid Type Description
780f
2 work process private
65338..65535
Inuse
3
Pin Pgsp Virtual Addr Range
1
0
3
The svmon -P command can be used to determine the top 10 processes using
memory, sorted in decreasing order, by the total pages reserved or being used
with the following command:
# svmon -Pv -t 10 | pg
78
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
10294 X
6579
1275
175
4642
N
N
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
1be3
65309..65535
8811
f3fe
4c09
2be5
472b
2647
e15c
4168
2965
694d
514a
9092
dbfb
...
Vsid
Esid
0
2 work process private
d
f
3
1
-
work
work
work
work
work
work
pers
pers
pers
pers
pers
pers
pers
shared library text
shared library data
shmat/mmap
code,/dev/hd2:18475
/dev/hd2:20485
/dev/hd2:20486
/dev/hd9var:2079
/dev/hd9var:2078
/dev/hd4:2
/dev/hd3:21
Type Description
0 work kernel seg
Inuse
3792
Pin Pgsp Virtual Addr Range
1265 175 3511
0..32767 :
580
8
0
579
0..675 :
2080
54
32
4
2
2
32
0
0
0
0
1
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-
473
39
32
4
2
2
-
0..65535
0..310
0..32783
0..32767
0..32768
0..32768
0..706
0..0
0..7
0..0
0..0
0..0
Inuse
Pin Pgsp Virtual Addr Range
3792 1265 175 3511
0..32767 :
65475..65535
8811
500a
d work shared library text
2 work process private
2080
122
0
1
0
0
473
122
65306..65535
20
b156
d81b
f work shared library data
- pers /dev/hd4:4286
1 pers code,/dev/hd2:10393
57
1
9
0
0
0
0
-
43
-
0..65535
0..122 :
0..425
0..0
0..8
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
5682 sendmail: a
6081
1266
175
4136
N
N
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
8811
51ea
d work shared library text
2 work process private
Inuse
3792
2080
107
Pin Pgsp Virtual Addr Range
1265 175 3511
0..32767 :
0
1
0
0
473
106
0..65535
0..103 :
Chapter 3. CPU and memory performance monitoring tools
79
65308..65535
29e5
71ee
59eb
f work shared library data
1 pers code,/dev/hd2:10755
- pers /dev/hd2:32701
60
38
4
0
0
0
0
-
46
-
0..417
0..106
0..9
Each column heading has the following meaning.
Pid
Indicates the process ID.
Command
Indicates the command the process is running.
Inuse
Indicates the total number of pages in real memory from
segments that are used by the process.
Pin
Indicates the total number of pages pinned from
segments that are used by the process.
Pgsp
Indicates the total number of pages used on paging space
by segments that are used by the process. This number is
reported only if the -r flag is not used.
Virtual
Indicates the total number of pages allocated in the
process virtual space.
64-bit
Indicates if the process is a 64-bit process (Y) or a 32-bit
process (N).
Mthrd
Indicates if the process is multi-threaded (Y) or not (N).
3.5.4 The svmon segment report
The segment report is printed when the -S flag is specified.
The svmon -S command has the following syntax:
svmon [-S [sid1...sidn] [ -u | -p | -g | -v ] [ -n | -s ] [ -w | -f | -c ]
[ -t count ] [ -i interval [N umIntervals ] ] [ -l ] [ -z ] [ -m ] ]
The svmon -S command produces the following output:
# svmon -S
Vsid
Esid Type Description
7162
- pers /dev/lv00:17
680d
- work misc kernel tables
80
Inuse
Pin Pgsp Virtual Addr Range
7638
0
0..100362
3819
0
0 3819
0..17054 :
63488..65535
0
- work kernel seg
3792
1265
175
3511
65475..65535
82b0
8811
- pers /dev/hd2:26992
- work
2390
2080
0
0
0
473
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
0..32767 :
0..2389
0..65535
...
6be5
67e6
8fdc
7be1
87de
- pers /dev/hd2:153907
- pers /dev/hd2:47135
- pers /dev/hd2:22746
- pers /dev/hd2:53296
- pers /dev/hd2:69859
0
0
0
0
0
0
0
0
0
0
-
-
0..2
0..1
0..0
0..12
0..0
To check the memory usage of the top five working segments according to the
number of virtual pages, use the following command:
# svmon -S -t 5 -w -v
Vsid
680d
Esid Type Description
- work misc kernel tables
Inuse
4197
Pin Pgsp Virtual Addr Range
0
0 4197
0..17064 :
63488..65535
0
- work kernel seg
3797
1270
175
3516
0..32767 :
65475..65535
700e
37ad
- work kernel pinned heap
- work
1919
770
624
1
0
0
1920
770
0..65535
0..764 :
65313..65535
a8a
- work
770
1
0
770
0..927 :
65250..65535
To print out the memory usage statistics of segments sorted by the number of
reserved paging space blocks, use the following command:
# svmon -S 680d 700e -g
Vsid
700e
680d
Esid Type Description
- work kernel pinned heap
- work misc kernel tables
Inuse
1919
4197
Pin Pgsp Virtual Addr Range
624
0 1920
0..65535
0
0 4197
0..17064 :
63488..65535
Each column heading has the following meaning.
Vsid
Indicates the virtual segment ID. Identifies a unique
segment in the VMM.
Esid
Indicates the effective segment ID. When provided, it
indicates how the segment is used by the process. If the
VSID segment is mapped by several processes, but with
different ESID values, then this field contains a -. In that
case, the exact ESID values can be obtained through the
Chapter 3. CPU and memory performance monitoring tools
81
-P option applied on each process identifier using the
segment.
Type
Identifies the type of the segment: pers indicates a
persistent segment, work indicates a working segment,
clnt indicates a client segment, map indicates a mapped
segment, and rmap indicates a real memory mapping
segment.
Description
Specifies a textual description of the segment. The value
of this column depends on the segment type. If the
segment is a persistent segment and is not associated
with a log, then the device name and inode number of the
associated file are displayed, separated by a colon. (The
device name and inode can be translated into a file name
with the ncheck command.) If the segment is the primary
segment of a large file, then the words large file are
prepended to the description. If the segment is a
persistent segment and is associated with a log, then the
string log is displayed.
If the segment is a working segment, then the svmon
command attempts to determine the role of the segment.
For instance, special working segments, such as the
kernel and shared library, are recognized by the svmon
command. If the segment is the private data segment for
a process, then private is printed out. If the segment is
the code segment for a process, and the segment report
is printed out in response to the -P flag, then the word
code is prepended to the description.
If the segment is mapped by several processes and used
in a different way (for example, a process private segment
mapped as shared memory by another process), then the
description is empty. The exact description can be
obtained through -P flag applied on each process
identifier using the segment.
If a segment description is too large to fit in the description
space then the description is truncated. The truncated
part can be obtained through the -S flag (without -l) on the
given segment.
82
Inuse
Indicates the number of pages in real memory in this
segment.
Pin
Indicates the number of pages pinned in this segment.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Pgsp
Indicates the number of pages used on paging space by
this segment. This field is relevant only for working
segments.
Virtual
Indicates the number of pages allocated for the virtual
space of the segment. (Only for working segments.)
VMM manages this value for statistical purposes. It may
not be updated. Then the value may be less than the
inuse counters.
Address Range
Specifies the range(s) the segment pages has been
allocated. The working segment may have two ranges,
because pages are allocated by starting from both ends
and moving towards the middle.
If the -l flag is present, the list of process identifiers that
use that segment is displayed. See the -l flag description
for special segments processing.
3.5.5 The svmon detailed segment report
The -D flag is used to get a more detailed listing of a segment.
The syntax of the svmon -D command is as follows:
svmon [-D sid1...sidn [-b] [ -i interval [ NumIntervals] ] [ -z ] ]
To print out the frames belonging to a segment, the command is as follows:
# svmon -D 700e
Segid: 700e
Type: working
Address Range: 0..65535
Size of page space allocation: 0 pages (
Virtual: 1920 frames ( 7.5 Mb)
Inuse: 1919 frames ( 7.5 Mb)
Page
65471
65535
0
1
2
3
4
5
6
7
Frame
313
311
314
309
308
305
296
299
294
297
0.0 Mb)
Pin
Y
N
Y
Y
Y
Y
Y
Y
Y
Y
Chapter 3. CPU and memory performance monitoring tools
83
...
381
8
9
10
292
295
290
Y
Y
Y
81019
380
379
3335
3336
3337
3338
3339
3341
3342
N
115074
80725
57367
59860
107421
114966
107433
95069
70192
N
N
Y
Y
N
N
N
Y
Y
To print out the frames belonging to a segment with the status bit of each frame,
use the following command:
# svmon -D 700e -b
Segid: 700e
Type: working
Address Range: 0..65535
Size of page space allocation: 0 pages (
Virtual: 1920 frames ( 7.5 Mb)
Inuse: 1919 frames ( 7.5 Mb)
...
381
84
Page
65471
65535
0
1
2
3
4
5
6
7
8
9
10
Frame
313
311
314
309
308
305
296
299
294
297
292
295
290
81019
380
379
3335
3336
3337
3338
N
115074
80725
57367
59860
107421
114966
0.0 Mb)
Pin
Y
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Ref
Y
N
N
N
Y
Y
N
N
N
N
N
N
N
N
N
N
Y
Y
N
N
Y
N
N
N
N
N
N
Mod
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
3339
3341
3342
107433
95069
70192
N
Y
Y
N
N
Y
Y
Y
Y
The output headings have the following meanings. The segid, type, address
range, size of page space allocation, and virtual and inuse headings are
explained at the end of 3.5.4, “The svmon segment report” on page 80.
Page
Relative page number to the virtual space. This page
number can be higher than the number of frames in a
segment (65532) if the virtual space is larger than a single
segment (large file).
Frame
Frame number in real memory.
Pin
Indicates if the frame is pinned or not.
Ref
Indicates if the frame has been referenced by a process
(-b option only).
Mod
Indicates if the frame has been modified by a process (-b
option only).
3.5.6 The svmon command report
The command report provides a usage summary of specific commands being
run. The command report is printed when the -C flag is specified.
The svmon -C command has the following syntax:
svmon [-C cmd1...cmdn [ -u | -p | -g | -v ] [ -n | -s [ -w | -f | -c ]
[ -t count] [ -i interval [ NumIntervals ] ] [ -d ] [ -l ] [ -z ] [ -m ] ]
To check the memory usage of specific commands, use the following command:
# svmon -C savevg ftp
# pg /tmp/file
===============================================================================
Command ftp
Inuse
Pin
Pgsp Virtual
42104
1271
175
3966
...............................................................................
SYSTEM segments
Inuse
Pin
Pgsp Virtual
3798
1270
175
3517
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
3798
Pin Pgsp Virtual Addr Range
1270 175 3517
0..32767 :
65475..65535
...............................................................................
Chapter 3. CPU and memory performance monitoring tools
85
EXCLUSIVE segments
Vsid
985e
322a
Inuse
36189
Pin
1
Esid Type Description
- pers /dev/lv00:17
2 work process private
65257..65535
22c
f work shared library data
64e
1 pers code,/dev/hd2:4550
1c88
- pers /dev/hd2:32628
Pgsp
0
Inuse
35977
112
Virtual
148
Pin Pgsp Virtual Addr Range
0
0..40307
1
0
109
0..83 :
53
44
3
0
0
0
0
-
39
0..849
0..57
0..2
...............................................................................
SHARED segments
Inuse
Pin
Pgsp Virtual
2117
0
0
301
Vsid
8811
Esid Type Description
d work shared library text
Inuse
2117
Pin Pgsp Virtual Addr Range
0
0
301
0..65535
===============================================================================
Command savevg
Inuse
Pin
Pgsp Virtual
savevg
*** command does not exist ***
If a command does not own a memory segment, the error, as shown above, will
be provided.
To check a command and display the memory statistics for the command, enter
the following:
# svmon -C ftp -d
===============================================================================
Command ftp
Inuse
Pin
Pgsp Virtual
46435
1266
175
3966
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
2728 ftp
46435
1266
175
3966
N
N
...............................................................................
SYSTEM segments
Inuse
Pin
Pgsp Virtual
3798
1265
175
3517
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
3798
Pin Pgsp Virtual Addr Range
1265 175 3517
0..32767 :
65475..65535
...............................................................................
EXCLUSIVE segments
Inuse
Pin
Pgsp Virtual
86
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
40520
Vsid
985e
322a
1
Esid Type Description
- pers /dev/lv00:17
2 work process private
65257..65535
22c
64e
1c88
f work shared library data
1 pers code,/dev/hd2:4550
- pers /dev/hd2:32628
0
Inuse
40308
112
148
Pin Pgsp Virtual Addr Range
0
0..40307
1
0
109
0..83 :
53
44
3
0
0
0
0
-
39
-
0..849
0..57
0..2
...............................................................................
SHARED segments
Inuse
Pin
Pgsp Virtual
2117
0
0
301
Vsid
8811
Esid Type Description
d work shared library text
Inuse
2117
Pin Pgsp Virtual Addr Range
0
0
301
0..65535
The column headings have the following meanings:
Command
Indicates the command name.
Inuse
Indicates the total number of pages in real memory in
segments that are used by the command (all process
running the command).
Pin
Indicates the total number of pages pinned in segments
that are used by the command (all process running the
command).
Pgsp
Indicates the total number of pages reserved or used on
paging space by segments that are used by the
command.
Virtual
Indicates the total number of pages allocated in the virtual
space of the command. Once this column heading is
displayed, svmon displays (if the -d flag is specified)
information about all the processes running the specified
command. It only contains the column headings of the
processes, as described in a process report. Then svmon
displays information about the segments used by those
processes.
This set of segments is separated into three categories:
The segments that are flagged as systems that are
shared by all processes the segments that are only used
by the set of processes, and the segments that are
shared between several command names.
Chapter 3. CPU and memory performance monitoring tools
87
If the -l flag is specified, then for each segment in the last
category, the list of process identifiers that use the
segment is displayed. The command name that the
process identifier runs is also displayed. See the -l flag
description for special segment processing.
3.5.7 The svmon Workload Manager (WLM) class report
The WLM (see 6.6, “Workload Manager (WLM)” on page 227, for information on
WLM) class report is printed when the -W flag is specified. The svmon -W
command has the following syntax:
svmon [ -W [class1...classn] [ -u | -p | - g | -v ] [ -n | -s ]
[ -w | -f | -c ] [ -t count ] [ -i interval [ NumIntervals ] ] [ -l ] [ -z ]
[ -m ] ]
Note: The svmon -W command should be run when Workload Manager is
started in order to create the printed workload class report.
To check the Workload Manager class statistics, enter the following command:
# svmon -W backup
==========================================================================
Superclass
Inuse
Pin Pgsp
Virtual
backup
52833
10 0
50329
Vsid
6784
1aa18
14356
173f5
5347
c34e
1891a
14636
5327
1d83f
1e33c
10772
6a84
15457
38a1
126f0
88
Esid Type
- work
- work
- pers
- pers
- work
- work
- work
- work
- work
- work
- work
- work
- work
- work
- work
- work
Description
/dev/lv_wlm1:17
/dev/lv_wlm2:17
Inuse
27989
21887
1250
1250
103
77
77
46
28
16
16
15
15
14
8
8
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Pin
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
Pgsp
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Virtual
28017
21887
101
77
77
37
20
18
13
13
13
14
8
8
==========================================================================
Superclass
Inuse
Pin Pgsp
Virtual
11313
- pers
/dev/hd1:26
6
0
e50c
b549
12e3
13351
14a16
12970
6904
a9c8
2320
-
work
work
work
work
work
work
work
work
pers
1d39f
834a
- pers
- pers
/dev/hd1:32
5
5
3
3
3
3
2
1
1
2
2
2
0
0
0
2
0
0
0
0
0
0
0
0
0
0
-
5
5
3
3
0
5
2
3
-
/dev/hd2:16870
/dev/hd1:23
1
1
0
0
-
-
The column headings in a Workload Manager class report have the following
meaning:
Class
Indicates the workload class name.
Inuse
Indicates the total number of pages in real memory in
segments belonging to the workload class.
Pin
Indicates the total number of pages pinned in segments
belonging to the workload class.
Pgsp
Indicates the total number of pages reserved or used on
paging space by segments belonging to the workload
class.
Virtual
Indicates the total number of pages allocated in the virtual
space of the workload class.
Once this column’s heading is displayed, svmon displays
information about the segments belonging to the workload
class.
If the -l option is specified, then for each segment, the list
of process identifiers that use the segment is displayed.
The workload class the process belongs to is also
displayed. See the -l flag description for special segments
processing.
Chapter 3. CPU and memory performance monitoring tools
89
Note: A process belongs to the workload class if its initial thread belongs to it.
3.5.8 The svmon command flags
The same flags for svmon are used by the different report types, with the
exception of the global and detailed segment reports.
Table 3-5 Commonly used flags of the svmon command
90
Flag
Description
-G
Displays a global report.
-P [ pid1... pidN ]
Displays memory usage statistics for process pid1...pidN.
pid is a decimal value. If no list of process IDs (PIDs) is
supplied, memory usage statistics are displayed for all
active processes.
-S [ sid1...sidN ]
Displays memory-usage statistics for segments sid1...sidN .
sid is a hexadecimal value. If no list of segment IDs (SIDs)
is supplied, memory usage statistics are displayed for all
defined segments.
-U [ lognm1...lognmN ]
Displays memory usage statistics for the login name
lognm1...lognmN. lognm is a string. It is an exact login
name. If no list of login identifiers is supplied, memory usage
statistics are displayed for all defined login identifiers.
-C cmd1...cmdN
Displays memory usage statistics for the processes running
the command name cmdnm1...cmdnmN. cmdnm is a string.
It is the exact base name of an executable file.
-W [ clnm1...clnmN ]
Displays memory usage statistics for the workload
management class clnm1...clnmN. clnm is a string. It is the
exact name of a class. If no list of class names is supplied,
memory usage statistics are displayed for all defined class
names.
-D sid1...sidN
Displays memory-usage statistics for segments sid1...sidN ,
and a detailed status of all the frames of each segment.
-n
Indicates that only non-system segments are to be included
in the statistics. By default, all segments are analyzed.
-s
Indicates that only system segments are to be included in
the statistics. By default, all segments are analyzed.
-w
Indicates that only working segments are to be included in
the statistics. By default, all segments are analyzed.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-f
Indicates that only persistent segments (files) are to be
included in the statistics. By default, all segments are
analyzed.
-c
Indicates that only client segments are to be included in the
statistics. By default, all segments are analyzed.
-u
Indicates that the objects to be printed are sorted in
decreasing order by the total number of pages in real
memory. It is the default sorting criteria if none of the
following flags are present: -p, -g, and -v.
-p
Indicates that the object to be printed is sorted in decreasing
order by the total number of pages pinned.
-g
Indicates that the object to be printed is sorted in decreasing
order by the total number of pages reserved or used on
paging space. This flag, in conjunction with the segment
report, shifts the non-working segment at the end of the
sorted list.
-v
Indicates that the object to be printed is sorted in decreasing
order by the total number of pages in virtual space. This flag,
in conjunction with the segment report, shifts the
non-working segment to the end of the sorted list.
-b
Shows the status of the reference and modified bits of all the
displayed frames (detailed report -D). Once shown, the
reference bit of the frame is reset. When used with the -i flag,
it detects which frames are accessed between each interval.
This flag should be used with caution because of its
performance impact.
-l
Shows, for each displayed segment, the list of process
identifiers that use the segment and, according to the type of
report, the entity name (login, command, or class) the
process belongs to. For special segments, a label is
displayed instead of the list of process identifiers.
System segment
This label is displayed for segments that are flagged
systems.
Unused segment
This label is displayed for segments that are not used by any
existing processes.
Shared library text
This label is displayed for segments that contain text of
shared library, and that may be used by most of the
processes (libc.a). This is to prevent the display of a long list
of processes.
Chapter 3. CPU and memory performance monitoring tools
91
Flag
Description
-z
Displays the maximum memory size dynamically allocated
(malloc) by svmon during its execution.
-m
Displays information about the source segment rather than
the mapping segment when a segment is mapping a source
segment.
-d
Displays the memory statistics of the processes belonging to
a given entity.
-t count
Displays memory usage statistics for the top count object to
be printed.
-i interval
[NumIntervals]
Instructs the svmon command to print statistics out
repetitively. Statistics are collected and printed every
interval seconds. NumIntervals is the number of repetitions;
if not specified, svmon runs until user interruption (Ctrl+C).
Note: If no command line flag is given, then the -G flag is implicit.
Because it may take a few seconds to collect statistics for some options, the
observed interval may be larger than the specified interval.
If none of the -u, -p, -g, and -v flags are specified, -u is implicit.
3.6 The rmss command
The rmss command provides you with a means to simulate different sizes of real
memory that are smaller than your actual machine, without having to extract and
replace memory boards or reconfigure memory using logical partitions.
Moreover, the rmss command provides a facility to run an application over a
range of memory sizes, displaying, for each memory size, performance statistics
such as the response time of the application and the amount of paging.
The main use for the rmss command is as a capacity planning tool, to determine
how much memory a workload needs. It can also be used as a problem
determination tool, particularly for those cases where having more memory
degrades performance.
To determine whether the rmss command is installed and available, run the
following command:
# lslpp -lI perfagent.tools
Fileset
Level State
Description
----------------------------------------------------------------------------
92
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Path: /usr/lib/objrepos
perfagent.tools
5.1.0.25
COMMITTED
Local Performance Analysis &
Control Commands
Path: /etc/objrepos
perfagent.tools
5.1.0.25
COMMITTED
Local Performance Analysis &
Control Commands
Note: The memory size simulated by the rmss command is the total size of the
machine's real memory, including the memory used by the operating system
and any other programs that may be running. It is not the amount of memory
used specifically by the application itself.
The rmss command can be invoked two ways:
1. To change the memory size and exit.
2. As a driver program that executes a specified application multiple times over
a range of memory sizes and displays important statistics that describe the
application's performance at each memory size.
The first invocation technique is useful when you want to get the look and feel of
how your application performs at a given system memory size, when your
application is too complex to be expressed as a single command, or when you
want to run multiple instances of the application. The second invocation
technique is appropriate when you have an application that can be invoked as an
executable program or shell script file.
The rmss command has the following syntax:
rmss
rmss
rmss
rmss
[ -s
-c MemSize
-r
-p
[ -d MemSize ] [ -f MemSize ] [ -n NumIterations ] [ -o OutputFile ]
MemSize ] Command
The commonly used flags are listed in Table 3-6.
Table 3-6 Commonly used flags of the rmss command
Flag
Description
-c MemSize
Changes the simulated memory size to the MemSize value, which is
an integer or decimal fraction in units of megabytes.
-d MemSize
Specifies the increment between memory sizes to be simulated.
-f MemSize
Specifies the final memory size.
Chapter 3. CPU and memory performance monitoring tools
93
Flag
Description
-r
Resets the simulated memory size to the real memory size of the
machine.
-s MemSize
Specifies the starting memory size.
-o OutputFile
Specifies the file into which to write the rmss report.
For example, to change the memory size to 500 MB, enter:
# rmss -c 500
Simulated memory size changed to 500 Mb.
To reset the memory size to the real memory size of the machine, enter:
# rmss -r
When any combination of the -s, -f, -d, -n, and -o flags is used, the rmss
command runs as a driver program, which executes a command multiple times
over a range of memory sizes, and displays statistics describing the command's
performance at each memory size.
An example of the report produced by the rmss command follows:
# rmss -s 1000 -f 900 -d 10 -n 1 -o /tmp/rmss.out cp /smit.log /dev/null
Hostname: server4.itsc.austin.ibm.com
Real memory size: 1024 Mb
Time of day: Wed Sep 18 15:24:13 2002
Command: cp/smit.log/dev/null
Simulated memory size initialized to 1000 Mb.
Number of iterations per memory size = 1 warmup + 1 measured = 2.
Memory size
Avg. Pageins
Avg. Response Time
Avg. Pagein Rate
(megabytes)
(sec.)
(pageins / sec.)
-----------------------------------------------------------------------1000
2.0
0.0
70.2
990
1.0
0.0
35.4
980
3.0
0.0
106.6
970
5.0
0.0
176.7
960
1.0
0.0
35.0
950
4.0
0.0
141.0
940
3.0
0.0
105.9
930
7.0
0.0
248.6
920
3.0
0.0
109.7
910
3.0
0.0
105.0
900
5.0
0.0
108.9
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Simulated final memory size.
The report consists of four columns.
 The left-most Memory Size column gives the memory size.
 The Avg. Pageins column gives the average number of page-ins that
occurred when the application was run at that memory size. It is important to
note that the Avg. Pageins column refers to all page-in operations, including
code, data, and file reads, from all programs that completed while the
application ran.
 The Avg. Response Time column gives the average amount of time it took the
application to complete.
 The Avg. Pagein Rate column gives the average rate of page-ins.
3.7 The topas command
The topas command reports vital statistics about activity on the local system
using a text-based output. It requires the AIX Version 5L (or later) perfagent.tools
fileset to be installed on the system. The topas command has received updates
since the time of writing, so check the AIX product documentation for additional
features. This command is a type of compilation of diagnostic commands, such
as sar, vmstat, iostat, and netstat. It allows you to see all of the statistics on
one screen so it is easy to observe interactions between them. The topas
command has the following syntax:
topas [ -d number_of_monitored_hot_disks ] [ -h ]
[ -i monitoring_interval_in_seconds ]
[ -n number_of_monitored_hot_network_interfaces ]
[ -p number_of_monitored_hot_processes ]
[ -w number_of_monitored_hot_WLM classes ] [ -c number_of_monitored_hot_CPUs ]
[ -P | -W ]
The commonly used flags are listed in Table 3-7.
Table 3-7 Commonly used flags of the topas command
Flag
Description
-i
Sets the monitoring interval in seconds. The default is 2 seconds.
-p
Specifies the number of hot processes to be monitored.
-w
Specifies the number of hot WorkLoad Manager (WLM) classes to be
monitored.
-c
Specifies the number of hot CPUs to be monitored.
Chapter 3. CPU and memory performance monitoring tools
95
3.7.1 Common uses of the topas command
Figure 3-1 on page 100 shows the standard topas command and its output. The
system host name is displayed on the top line of the screen. The line below
shows the time and date as well as the sample interval used for measurement.
CPU utilization statistics
CPU utilization is graphically and numerically displayed below the date and time
and is split up into a percentage of idle, wait, user, and kernel time.
Idle time
The percentage of time when the processor is not
performing any tasks
Wait time
The percentage of time when the CPU is waiting for the
response of an input output device such as a disk or
network adapter
User time
The percentage of time when the CPU is executing a
program in user mode
Kernel time
The percentage of time when the CPU is running in kernel
mode
Network interface statistics
The following network statistics are available over the monitoring period.
Network
The name of the interface adapter
KBPS
Reports the total throughput of the interface in kilobytes
per second
I-Pack
Reports the number of packets received per second
O-Pack
Reports the number of packets sent per second
KB-In
Reports the number of kilobytes received per second
KB-Out
Reports the number of kilobytes sent per second
Disk drive statistics
The following disk drive statistics are available.
96
Disk
The name of the disk drive.
Busy%
Reports the percentage of time that the disk drive was
active.
KBPS
Reports the total throughput of the disk in kilobytes per
second. This value is the sum of KB-Read and KB-Writ.
TPS
Reports the number of transfers per second or I/O
requests to a disk drive.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
KB-Read
Reports the number of kilobytes read per second.
KB-Writ
Reports the number of kilobytes written per second.
Process statistics
The top hot processes are displayed with the following headings.
Name
The name of the process. Where the number of
characters in the process name exceeds nine, the name
will be truncated. No path name details for the process
are displayed.
PID
Shows the process identification number for the process.
This is useful when a process needs to be stopped.
CPU%
Reports on the CPU time utilized by this process.
PgSp
Reports on the paging space that has been allocated to
this process.
Owner
Displays the owner of the process.
Event and queue statistics
This part of the report is on the right-hand side of the topas display screen and
reports on select system global events and queues over the sampling interval.
Cswitch
Reports the number of context switches per second
Syscall
Reports the total number of system calls per second
Reads
Reports the number of read system calls per second
Writes
Reports the number of write system calls per second
Forks
Reports the number of fork system calls per second
Execs
Reports the number of exec system calls per second
Runqueue
Reports the average number of threads that were ready to
run, but were waiting for a processor to become available
Waitqueue
Reports the average number of threads waiting for paging
to complete
File and tty statistics
The file and tty part of the topas display is located on the extreme right-hand side
at the top. The reported items are listed below.
Readch
Reports the number of bytes read through the read
system call per second
Writech
Reports the number of bytes written through the write
system call per second
Chapter 3. CPU and memory performance monitoring tools
97
Rawin
Reports the number of bytes read in from a tty device per
second
Ttyout
Reports the number of bytes written to a tty device per
second
Igets
Reports on the number of calls per second to the inode
lookup routines
Namei
Reports the number of calls per second to the path lookup
routine
Dirblk
Reports on the number of directory blocks scanned per
second by the directory search routine
Paging statistics
There are two parts of the paging statistics reported by topas. The first part is
total paging statistics. This simply reports the total amount of paging available on
the system and the percentages free and used. The second part provides a
breakdown of the paging activity. The reported items and their meanings are
listed below.
Faults
Reports the number of faults
Steals
Reports the number of 4-KB pages of memory stolen by
the Virtual Memory Manager per second
PgspIn
Reports the number of 4-KB pages read in from the
paging space per second
PgspOut
Reports the number of 4-KB pages written to the paging
space per second
PageIn
Reports the number of 4-KB pages read per second
PageOut
Reports the number of 4-KB pages written per second
Sios
Reports the number of input/output requests per second
issued by the Virtual Memory Manager
Memory statistics
The memory statistics are listed below.
98
Real
Shows the actual physical memory of the system in
megabytes
%Comp
Reports real memory allocated to computational pages
%Noncomp
Reports real memory allocated to non-computational
pages
%Client
Reports on the amount of memory that is currently used
to cache remotely mounted files
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
NFS statistics
Statistics for client and server calls per second are displayed.
WLM classes
This subsection displays a list of hot WorkLoad Manager (WLM) Classes. The
maximum number of WLM classes displayed is the number of hot WLM classes
being monitored as specified with the -w flag. A smaller number of classes will be
displayed if other subsections are also being displayed. Pressing the w key turns
off this subsection. The following fields are displayed for each class:
%CPU Utilization
The average CPU utilization of the WLM class over the
monitoring interval.
%Mem Utilization
The average memory utilization of the WLM class over the
monitoring interval.
%Blk I/O
The average percent of block I/O of the WLM class over
the monitoring interval. When this subsection first displays
the list of hot WLM classes, the list will be sorted by the
CPU% field. However, the list can be sorted by the other
fields by moving the cursor to the top of the desired
column.
Processes
This subsection displays a list of hot processes. The maximum number of
Processes displayed is the number of hot processes being monitored as
specified with the -p flag. A smaller number of processes will be displayed if other
subsections are also being displayed. Pressing the p key turns off this
subsection. The processes are sorted by their CPU usage over the monitoring
interval. The following fields are displayed for each process:
 Name
The name of the executable program executing in the process. The name is
stripped of any path name and argument information and truncated to nine
characters in length.
 Process ID
The process ID of the process.
 %CPU Utilization
The average CPU utilization of the process over the monitoring interval. The
first time a process is shown, this value is the average CPU utilization over
the lifetime of the process.
Chapter 3. CPU and memory performance monitoring tools
99
 Paging Space Used
The size of the paging space allocated to this process. This can be
considered an expression of the footprint of the process but does not include
the memory used to keep the executable program and any shared libraries it
may depend on.
 Process Owner (if the WLM section is off)
The user name of the user who owns the process.
 WorkLoad Management (WLM) Class (if the WLM section is on)
The WLM class to which the process belongs.
Note: In order to obtain a meaningful output from the topas command, the
screen or graphics window must support a minimum of 80 characters by 24
lines. If the display is smaller than this, then parts of the output become
illegible.
The output of the topas command is shown in Figure 3-1.
Figure 3-1 The topas command output
In AIX 5L Version 5.1, the topas program has been enhanced to add two
alternate screens, the CPU utilization report has become an optional subsection,
and the fixed section includes an additional subsection with NFS statistics, while
100
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
the variable section includes a new WLM subsection. The first alternate screen
(reachable with the P command or the -P flag), presents the list of busiest
processes, similar to the processes subsection of the main screen, but with more
columns. This screen is sortable by any of its columns. The second alternate
screen (reachable with the W command, or the -W flag), is divided into two
sections. The top section is the same list of busiest WLM classes as presented in
the WLM subsection of the main screen, also sortable by any of its columns.
When the user selects one the WLM classes shown using the arrow keys and the
f key, the second section of the screen will show the list of hot processes within
the selected WLM class.
While topas is running, it accepts one-character subcommands. Each time the
monitoring interval elapses, the program checks for one of the following
subcommands and responds to the action requested:
a
The a key shows all of the variable subsections being monitored (CPU,
network, disk, WLM, and process). Pressing the a key always returns the
topas command to the initial main display.
c
The c key toggles the CPU subsection between the cumulative report,
off, and a list of the busiest CPUs. The number of busiest CPUs
displayed will depend upon the space available on the screen.
d
The d key toggles the disk subsection between a list of busiest disks, off,
and the report on the total disk activity of the system. The number of
busiest disks displayed will depend upon the space available on the
screen.
h
The h key shows the help screen.
n
The n key toggles the network interfaces subsection between a list of
busiest interfaces, off, and the report on the total network activity of the
system. The number of busiest interfaces displayed will depend upon the
space available on the screen.
w
The w key toggles the WorkLoad Management (WLM) classes
subsection on and off. The number of busiest WLM classes displayed will
depend upon the space available on the screen.
p
The p key toggles the hot processes subsection on and off. The number
of busiest processes displayed will depend upon the space available on
the screen.
P
The uppercase P key replaces the default display with the full-screen
process display. This display provides more detailed information about
processes running on the system than the process section of the main
display. When the P key is pressed again, it toggles back to the default
main display.
Chapter 3. CPU and memory performance monitoring tools
101
W
The uppercase W key replaces the default display with the full-screen
WLM class display. This display provides more detailed information about
WLM classes and processes assigned to classes. When the W key is
pressed again, it toggles back to the default main display.
f
Moving the cursor over a WLM class and pressing the f key displays the
list of top processes in the class at the bottom of the WLM screen. This
key is valid only when topas is in the full-screen WLM display (by using
the W key or the -W flag).
q
Quits the program.
r
Refreshes the display.
Check the latest documentation for a full set of subcommands and command line
options.
3.8 The emstat command
The PowerPC architecture no longer supports, in hardware, 35 POWER
instructions. To maintain compatibility with older binaries (which may contain
these deleted instructions), the AIX Version 4 kernel includes emulation routines
that provide support for the deleted instructions. Attempting to execute a deleted
instruction results in an illegal instruction exception. The kernel decodes the
illegal instruction, and, if it is a deleted instruction, the kernel runs an emulation
routine that functionally emulates the instruction.
The emstat command reports statistics regarding how many instructions the
system must emulate. The emulated instruction count should be used to
determine if an application needs to be recompiled to eliminate instructions that
must be emulated on 601 PowerPC, 604 PowerPC, RS64, or other non-POWER
processors. If an instruction must be emulated, more CPU cycles are required to
execute this instruction than an instruction that does not have to be emulated.
Most emulation problems are seen on older PowerPC 604 systems. A typical
example is a PowerPC 601 system that is upgraded to a 604 system. If
performance slows down instead of improving, it is most likely due to emulation.
The solution to emulation is to recompile the application in common mode. The
default architecture platform for compilations on AIX Version 4 is common
architecture. However, the default architecture on AIX Version 3 was for
POWER, POWER2, and PowerPC 601. If these binaries ran on a PowerPC 604,
some instructions may be emulated.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
To determine whether the emstat command is installed and available, run the
following command:
# lslpp -l bos.adt.samples
Note: In AIX 5L, the emstat command is located in the perfagent.tools fileset.
The emstat command works similarly to the vmstat command in that you specify
an interval time in seconds, and, optionally, the number of intervals. The value in
the first column is the cumulative count since system boot, while the value in the
second column is the number of instructions emulated during the specified
interval. Emulations on the order of many thousands per second can have an
impact on performance:
# /usr/samples/kernel/emstat 2
emstat total count
emstat interval count
965
965
965
0
965
0
965
0
965
0
967
2
967
0
967
0
974
7
974
0
974
0
974
0
974
0
974
0
1284
310
2171
887
3325
1154
Once emulation has been detected, the next step is to determine which
application is emulating instructions. This is much harder to determine. One way
is to run only one application at a time and monitor it with the emstat program.
3.9 The /proc file system
AIX 5L provides support of the /proc file system. This pseudo file system maps
processes and kernel data structures to corresponding files.
Chapter 3. CPU and memory performance monitoring tools
103
The output of the mount and df commands showing /proc is provided in the
following examples:
# mount
node
mounted
-------- --------------/dev/hd4
/dev/hd2
/dev/hd9var
/dev/hd3
/dev/hd1
/proc
# df
Filesystem
/dev/hd4
/dev/hd2
/dev/hd9var
/dev/hd3
/dev/hd1
/proc
mounted over
--------------/
/usr
/var
/tmp
/home
/proc
512-blocks
65536
1507328
32768
557056
32768
-
Free %Used
27760
58%
242872
84%
16432
50%
538008
4%
31608
4%
-
vfs
-----jfs
jfs
jfs
jfs
jfs
procfs
date
-----------Sep 11 16:52
Sep 11 16:52
Sep 11 16:52
Sep 11 16:52
Sep 11 16:53
Sep 11 16:53
options
--------------rw,log=/dev/hd8
rw,log=/dev/hd8
rw,log=/dev/hd8
rw,log=/dev/hd8
rw,log=/dev/hd8
rw
Iused %Iused Mounted on
2239
14% /
22437
12% /usr
448
11% /var
103
1% /tmp
47
2% /home
- /proc
The entry in the /etc/vfs file appears as follows:
# lsvfs procfs
procfs 6
none
none
Each process is assigned a directory entry in the /proc file system with a name
identical to its process ID. In this directory, several files and subdirectories are
created corresponding to internal process control data structures. Most of these
files are read-only, but some of them can also be written to and be used for
process control purposes. The interfaces to these files are the standard C
language subroutines open(), read(), write(), and close(). It is possible to have
several concurrent readers, but for reliability reasons, the first write access
should use the exclusive flag, so that subsequent opens for write access fail. The
description of the data structures used can be found in /usr/include/sys/procfs.h.
The ownership of the files in the /proc file system is the same as for the
processes they represent. Therefore, regular users can only access /proc files
that belong to their own processes.
A simple example illustrates this further. Suppose a process is waiting for
standard input (the information in the process data structures is basically static).
If you look at an active process, a lot of the information would constantly change:
# ls -l /proc/19082/
total 0
dr-xr-xr-x
1 root
dr-xr-xr-x
1 root
-rw------1 root
104
system
system
system
0 Sep 15 15:12 .
0 Sep 15 15:12 ..
0 Sep 15 15:12 as
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
-r---------w------dr-xr-xr-x
-r-------dr-x------r--r--r--r--------r--------r--r--r--
1
1
1
1
1
1
1
1
1
root
root
root
root
root
root
root
root
root
system
system
system
system
system
system
system
system
system
128
0
0
0
0
448
1024
1520
0
Sep
Sep
Sep
Sep
Sep
Sep
Sep
Sep
Sep
15
15
15
15
15
15
15
15
15
15:12
15:12
15:12
15:12
15:12
15:12
15:12
15:12
15:12
cred
ctl
lwp
map
object
psinfo
sigact
status
sysent
Table 3-8 provides the function of the pseudo files listed in the previous output.
Table 3-8 Function of pseudo files in /proc/<pid> directory
Pseudo file name
Function
as
Read/write access to address space
cred
Credentials
ctl
Write access to control process, for example, stop or resume
lwp directory
Kernel thread information
map
Virtual address map
object directory
Map file names
psinfo
Information for the ps command; readable by everyone
sigact
Signal status
status
Process state information, such as address, size of heap, or
stack
sysent
Information about system calls
The pseudo file named as allows you to access the address space of the
process, and as it can be seen by the rw (read/write) access flags, you can read
and write to the memory belonging to the process.
It should be understood that only the user regions of the process' address can be
written to under /proc. Also, a copy of the address space of the process is made
while tracing under /proc. This is the address space that can be modified. This is
done so when the as file is closed; the original address space is unmodified.
The cred file provides information about the credentials associated with this
process. Writing to the ctl file allows you to control the process; for example, to
stop or to resume it. The map file allows access to the virtual address map of the
process. Information usually shown by the ps command can be found in the
psinfo file, which is readable for all system users. The current status of all signals
Chapter 3. CPU and memory performance monitoring tools
105
associated with this process is recorded in the sigact file. State information for
this process, such as the address and size of the process heap and stack
(among others), can be found in the status file. Finally, the sysent file allows you
to check for the system calls available to this process.
The object directory contains files with names as they appear in the map file.
These files correspond to files mapped in the address space of the process. For
example, the content of this directory appears as follows:
# ls -l /proc/19082/object
total 13192
dr-x-----1 root
system
dr-xr-xr-x
1 root
system
-r-xr-xr-x
1 bin
bin
-rwxr-xr-x
1 bin
bin
-r-xr-xr-x
2 bin
bin
-r--r--r-1 bin
bin
-r-xr-xr-x
1 bin
bin
-r--r--r-1 bin
bin
-r-xr-xr-x
1 bin
bin
0
0
6264
14342
6209308
118267
11009
377400
6264
Sep
Sep
Aug
Aug
Aug
Aug
Aug
Aug
Aug
15
15
24
22
24
24
24
24
24
15:09
15:09
21:16
22:37
13:03
15:06
14:59
15:05
21:16
.
..
a.out
jfs.10.5.10592
jfs.10.5.2066
jfs.10.5.2076
jfs.10.5.4129
jfs.10.5.4161
jfs.10.5.6371
The a.out file always represents the executable binary file for the program
running in the process itself. Because the example program is written in C and
must use the C runtime library, it can be concluded from the size of the entry
named jfs.10.5.2066 that this corresponds to the /usr/ccs/lib/libc.a file. Checking
this file reveals that the numbers in the file name are the major and minor device
numbers, and the inode number, respectively. This can be seen in the following
output, where /usr corresponds to /dev/hd2 and the ncheck command is used to
find a file belonging to an inode in a specific file system:
# ls -l /dev/hd2
brw-rw---1 root
system
# ncheck -i 2066 /dev/hd2
/dev/hd2:
2066
/ccs/lib/libc.a
10,
5 Sep 20 16:09 /dev/hd2
The lwp directory has subdirectory entries for each kernel thread running in the
process. The term lwp stands for lightweight process and is the same as the
term thread used in the AIX documentation. It is used in the context of the /proc
file system to keep a common terminology with the /proc implementation of other
operating systems. The names of the subdirectories are the thread IDs. The test
program has only one thread with the ID 54891, as shown in the output of the ps
command. Therefore, only the content of this one thread directory is shown:
# ps -mo THREAD -p 19082
USER
PID PPID
TID ST
root 19082 20678
- A
- 54891 S
# ls -l /proc/19082/lwp/54891
106
CP PRI SC
WCHAN
0 83 1 700e6244
0 83 1 700e6244
F
200001
10400
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
TT BND COMMAND
pts/3
- wc
- -
total 0
dr-xr-xr-x
dr-xr-xr-x
--w-------r--r--r--r--------
1
1
1
1
1
root
root
root
root
root
system
system
system
system
system
0
0
0
120
1200
Sep
Sep
Sep
Sep
Sep
15
15
15
15
15
15:03
15:03
15:03
15:03
15:03
.
..
lwpctl
lwpsinfo
lwpstatus
The lwpctl, lwpsinfo, and lwpstatus files contain thread-specific information to
control this thread, for the ps command, and about the state, similar to the
corresponding files in the /proc/pid directory.
As an example of what can be obtained from reading these files, the following
lines show the content of the cred file (after the use of the od command):
# ls -l /proc/19082/cred
-r-------1 root
system
# od -x /proc/19082/cred
0000000 0000 0000 0000 0000 0000
*
0000160 0000 0000 0000 0007 0000
0000200 0000 0000 0000 0002 0000
0000220 0000 0000 0000 0007 0000
0000240 0000 0000 0000 000a 0000
0000260
128 Sep 15 15:07 /proc/19082/cred
0000 0000 0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0003
0008
000b
The output shows, in the leftmost column, the byte offset of the file in octal
representation. The remainder of the lines are the actual content of the file in
hexadecimal notation. Even if the directory listing shows the size of the file to be
128 bytes or 0200 bytes in octal, the actual output is 0260 or 176 bytes in size.
This is due to the dynamic behavior of the last field in the corresponding
structure. The digit 7 in the line with the number 0160 specifies the number of
groups the user ID running this process belongs to. Because every user ID is at
least part of its primary group, but belongs possibly to a number of other groups
that cannot be known in advance, only space for the primary group is reserved in
the cred data structure. In this case, the primary group ID is zero because the
user ID running this process is root. Reading the complete content of the file,
nevertheless, reveals all the other group IDs the user currently belongs to. The
group IDs in this case (2, 3, 7, 8, 0xa (10), and 0xb (11)) map to the groups bin,
sys, security, cron, audit, and lp. This is exactly the set of groups the user ID root
belongs to by default.
3.10 General performance guidelines
Table 3-9 on page 108 lists some general rule-of-thumb formula for investigating
system performance.
Chapter 3. CPU and memory performance monitoring tools
107
Table 3-9 General performance guidlines
Formula
Command
Description
%usr + %sys <
80%
sar
vmstat
If %usr and %sys are greater than 80 percent, then
the system may be CPU bound.
po / fr > 1/h
vmstat
If the ratio of po:fr is greater than 1–6, then the
system may be thrashing.
fr / sr = high
vmstat
If the ratio of fr:sr is high, then the system may be
over committing memory.
%user + %sys
> 70%
iostat
If utilization is greater than 70 percent processes
are waiting longer than necessary for I/O to
complete, as most processes sleep while waiting
for their I/O request to complete.
3.11 Quiz
The following assessment questions help verify your understanding of the topics
discussed in this chapter.
1. When monitoring a system with vmstat, which of the following values under
the cpu heading would indicate that the system is probably CPU bound?
A.
The value of wa is greater than 70.
B.
The value of id is greater than 70.
C. The sum of us and sy is consistently between 99 and 100.
D.
The sum of id and wa is consistently between 99 and 100.
2. Which of the following commands should be used to show the number of
system calls per second that are being executed?
A.
pstat
B.
vmstat
C. filemon
D.
lockstat
3. When using vmstat with intervals, which of the following describes the values
of the first line of statistics?
A.
Averages since the system boot
B.
Averages since the top of the hour
C. Averages since the beginning of the day
D.
108
Averages since the beginning of the month
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
4. Using the report from vmstat -s, as shown in the exhibit, which of the
following indicates how the paging statistics can be improved?
vmstat -s
11228009
1791982
419439
221142
231045
0
3461761
10630
3298154
52
1199652
76372
0
0
0
254265
823719
823719
43493481
140637006
0
0
85003313
total address trans. faults
page ins
page outs
paging space page ins
paging space page outs
total reclaims
zero filled pages faults
executable filled pages faults
pages examined by clock
revolutions of the clock hand
pages freed by the clock
backtracks
lock misses
free frame waits
extend XPT waits
pending I/O waits
start I/Os
iodones
cpu context switches
device interrupts
software interrupts
traps
syscalls
A.
Add paging space.
B.
Increase CPU power.
C. Add physical memory.
D.
Reduce the number of system calls.
5. When monitoring a system using vmstat with an interval, which of the
following conclusions should be drawn about the metrics under page pi and
page po?
A.
Occasional small numbers are normal.
B.
Any non-zero value of pi or po indicates a RAM shortage.
C. Any non-zero value of pi or po indicates a paging space shortage.
D.
Large values are normal only on multi-processor systems.
Chapter 3. CPU and memory performance monitoring tools
109
6. When monitoring a system using /usr/bin/vmstat with an interval, how does
the size of the interval affect the page pi and page po metrics?
A.
It should not; the metric is in pages per second.
B.
The larger the interval, the larger the values.
C. The interval only affects the first data line of output.
D.
The interval only affects the pi column, not the po column.
7. Which of the following commands will display the total number of pages
paged out to paging space since the system was booted?
A.
lsps
B.
iostat
C. uptime
D.
/usr/bin/vmstat -s
8. Which of the following tools should be used to analyze memory usage for the
whole system at a point in time?
A.
iostat
B.
svmon
C. netstat
D.
filemon
9. In order to obtain a list of the top memory users on an AIX Version 4 system,
which of the following commands should be used?
A.
pstat
B.
tprof
C. svmon
D.
filemon
10.Using the ps -el output, as shown in the exhibit, which of the following
conclusions is most appropriate to draw?
F
S UID PID PPID
202803 S 0
1
0
260801 S 0
140 1
6
240801 S 0
169 1
4
260801 S 0
244 1
8
240801 S 0
283 1
6
110
C
0
0
PRI NI ADDR SZ WCAN
60 20 1004 528
60 20 4550 208
0
60
0
0
-
TIME
CMD
131:33 init
0:00
srcmstr
-
0:01
cron
60
20 37cd 176 5a6a02
4
20 5d57 144
-
3:18
portmap
60
20 34cd
-
42:42
syncd
72 5e3439
8
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
TTY
F
S UID PID PPID
42801 S 0
360 1
6
260801 S 0
525 1
5
240801 S 0
554 1
1
240801 S 200 575 7998
0
9
260801 S 0
604 1
0
60801 S 0
629 1
9
240801 S 0
650 1406
2
40001 S 0
665 1
9
C
0
PRI NI ADDR SZ WCAN
60 20 50d4 284 cc98
0
60
0
TTY
-
TIME
0:01
20 5535 148
-
1:00
CMD
errdemo
n
syslogd
59
20 7d9f
-
0:00
llbd
0
60
20 a83
-ksh
0
60
20 1565 468
pts/1 0:00
0
- 7:53
0
60
20 2d6b 224
0
60
0
23
20 14e7 184 12d044
- 0:05
0
3aae 312 1fca54 hft/0 0:32
--
60 3f2f8
180
-
0:00
snmpd
x_st_mg
r
qdaemon
userpro
g
A.
The snmpd process is running at a fixed priority of 60.
B.
If both the syncd process and the portmap process become runable at
the same time, then the syncd process would get scheduled first.
C. If both the userprog process and the qdaemon process become runable
at the same time, then the qdaemon process would get scheduled first.
D.
If both the syslogd process and the llbd process become runable at the
same time, then the llbd process would get scheduled first.
11.Which of the following general operation techniques will best provide a
measurable performance improvement of a system?
A.
Attach SCSI devices in ID order.
B.
Perform backups at regular intervals.
C. Perform regular preventative maintenance of devices with moving parts.
D.
Reschedule the processing to balance the workload.
Chapter 3. CPU and memory performance monitoring tools
111
12.A developer tried to run a sar report and received the following error:
sar:0551-201 cannot open /usr/adm/sa/sa12
Which of the following procedures should be performed so that the developer
can obtain sar reports?
A.
Run bosboot -a -L.
B.
Edit inittab to collect data.
C. Edit crontab to start collecting data.
D.
Run bosboot -ad /dev/ipldevice and then reboot.
13.After a migration from an older POWER server to a PowerPC-based server,
users complain about decreased performance. Which of the following tools
should be used to investigate the performance problem?
A.
netstat
B.
iostat
C. perfpmr
D.
emstat
14.To examine the Exhibit, press the Exhibit button. Which of the following
conclusions is most appropriate to be drawn from looking at the topas output?
A.
The system is an AIX 5.x and WLM has been installed.
B.
The system is an AIX 4.x and WLM has been installed.
C. From the command line, topas -d2 -i4 -n2 -p20 -w2 -c2 was run on an
AIX 5.x system.
D.
From the command line, topas -d2 -i2 -n2 -p20 -w2 -c2 was run on an
AIX 4.x system.
15.A system administrator wishes to display the five most active processes and
the two most active WLM classes but no disk information every 5 seconds.
Which of the following commands would accomplish this?
A.
topas -i5 -w0 -p0
B.
topas -i5 -p5 -n0 -d0 -w0
C. topas -i5 -p5 -d0
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
16.Which of the following is true about the page-in and page-out metrics
produced by vmstat -s output?
A.
Only file space for page-ins and page-outs is included.
B.
Only client paging for page-ins and page-outs is included.
C. Only paging space for page-ins and page-outs is included.
D.
Paging to both the file space and paging space is included.
17.Which of the following is true of vmstat on AIX 5L?
A.
The re column always shows 0.
B.
The b column is always 0 for SMP machines.
C. The sum of us, sys, id, and wa is always 100.
D.
The sum of r and b is equal to the number of CPUs times two.
18.When monitoring a system using vmstat with an interval, which of the
following conclusions should be drawn about the metrics under page pi and
page po?
A.
If pi is twice the value of po then more RAM is needed.
B.
If po is zero and pi is high it does not indicate a memory shortage.
C. If po is zero and pi is high there is not enough paging on the system.
D.
The pi/po ratio should never be greater than 1 unless both values are 0.
19.Which of the following options from vmstat indicates that a system is
thrashing?
A.
po/fr > 1/h
B.
(fr/sr) > re
C. (maxperm/minperm) > po
D.
re > 0
20.What information does the line jfs.10.5.2002 provide in the following
example?
/proc/9808/object>#ls -l
total 0
dr-xr-xr-x
1 root
printq
dr-xr-xr-x
1 root
system
-r-xr-xr-x
1 bin
bin
-rwxr-xr-x
1 bin
bin
Oct
Oct
Oct
Oct
5
5
5
5
10:34 .
10:34 ..
10:34 a.out
10:34 jfs.10.5.2002
A.
The first two numbers are the major/minor numbers and the 2002 is the
inode number for the process.
B.
The first two numbers are date related and the 2002 is the process ID.
Chapter 3. CPU and memory performance monitoring tools
113
C. The ncheck -s command is run against the jfs.10.5.2002 file to determine
what the inode is for the process.
D.
An od -x /proc/9808/object/jfs.10.5.2002 will give me the primary group,
user ID, and current size of the running process.
21.Which of the following commands would a system administrator run to view
memory usage by segment?
A.
svmon
B.
tprof
C. dbx
D.
bootinfo
22.To get a general idea of memory utilization of a system at the current
moment, which of the following commands should be used?
A.
ps aux
B.
lsps -s
C. bootinfo -r
D.
iostat 5 5
23.Which of the following performance tools will provide source statement
profiling and a summary of all CPU usage?
A.
prof
B.
gprof
C. tprof
D.
114
kprof
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
3.11.1 Answers
The following are the preferred answers to the questions provided in this section.
1. C
2. B
3. A
4. C
5. A
6. A
7. D
8. B
9. C
10.D
11.D
12.C
13.D
14.A
15.C
16.D
17.A
18.B
19.A
20.A
21.A
22.A
23.C
3.12 Exercises
The following exercises provide sample topics for self study. They will help
ensure comprehension of this chapter.
1. Describe how the sar command is set up to collect historical data.
2. Describe the differences between the sa1 and sa2 commands.
Chapter 3. CPU and memory performance monitoring tools
115
3. Describe how the crontab is modified to allow sar to collect data.
4. When running the vmstat command, there are either five or six measurement
columns; describe all five or six and show the flag required for the sixth
column.
5. Describe how a system could be described as CPU bound using the vmstat
command. Also, what are the percentages for single- and multi-processor
systems?
6. Name the seven types of reports the svmon command creates and give a brief
description of each.
7. Which svmon command flags are used to display a programs resource
utilization?
8. Which svmon command flags are used to display a user resource utilization on
the system?
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
4
Chapter 4.
Disk I/O performance
monitoring tools
The following topics are discussed in this chapter:
 Logical Volume Manager (LVM) performance analysis, using the lslv
command
 Journaled file system (JFS) performance analysis tools, using the filemon
and fileplace commands
All topics and tools discussed in this chapter will provide you with a set of
methods for determining logical volume manager, file system, and disk I/O
related performance issues.
© Copyright IBM Corp. 2002. All rights reserved.
117
4.1 Overview
With the AIX operating system, the handling of disk-related I/O is based upon
different functional levels, as shown in Figure 4-1.
Figure 4-1 Disk, LVM, and file system levels
The lowest level is the physical level and consists of device drivers accessing the
physical disks and using the corresponding adapters. The next level is the logical
level, managed by the Logical Volume Manager (LVM), which controls the
physical disk resources. The LVM provides a logical mapping of disk resources
to the application level. The application level can consist of either the journaled
file system (JFS) or raw access, for example, used by relational database
systems.
The performance analysis tools discussed in the following section focus on the
logical level (LVM) and on the application level (JFS). The monitoring of the
physical level is primarily done by using the iostat command, which is described
in 4.2, “The iostat command” on page 118.
Covering the entire subject of the AIX Logical Volume Manager is beyond the
scope of this publication. For more background information on the AIX Logical
Volume Manager, refer to AIX Logical Volume Manager From A to Z: Introduction
and Concepts, SG24-5432, as well as the AIX Version System Management
Guide: Operating System and Devices, SC23-2525.
4.2 The iostat command
The iostat command is a useful tool that provides a first indication of I/O-related
performance problems. The iostat command is capable of reporting CPU
statistics, terminal I/O statistics, and disk I/O statistics, which help identify the I/O
load on individual components, such as hard disks.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The information from iostat reports can be used to modify system
configurations to improve I/O load distribution between physical disks. The
iostat command extracts data from AIX kernel I/O counters in the kernel
address space, which are updated at every clock tick (1/100 second) for TTY as
well as CPU and I/O subsystem activity.
The syntax of the iostat command is as follows:
iostat [-d | -t] [physicalVolume ...] [interval [count]]
The commonly used flags are provided in Table 4-1.
Table 4-1 Commonly used flags of the iostat command
Flag
Description
-d
This flag displays only the disk utilization report. The -d flag is
exclusive of the -t flag.
-t
This flag displays only the TTY and CPU usage. The -t flag is
exclusive of the -d flag.
By using the physicalVolume parameter (by specifying the physical volume (PV)
name of the individual disk or CD-ROM), iostat generates an I/O report only for
the specified PVs. If no PVs are specified, the iostat command generates a
report for all drives.
The interval parameter specifies the amount of time in seconds between each
report. The count parameter specifies the number of I/O reports generated. If the
interval parameter is specified without the count parameter, the iostat command
generates reports continuously.
An example of the iostat command is as follows:
# iostat 1 2
tty:
Disks:
hdisk3
hdisk2
hdisk0
hdisk1
cd0
hdisk4
tin
0.0
tout
41.4
% tm_act
0.0
0.1
0.0
0.1
0.0
0.0
avg-cpu:
Kbps
0.3
1.1
0.9
1.5
0.0
0.2
% user
61.1
tps
0.0
0.0
0.1
0.0
0.0
0.0
% sys
0.1
Kb_read
258032
258088
746152
974788
0
323080
% idle
38.9
% iowait
0.0
Kb_wrtn
224266
1658678
725871
1660027
0
40480
Chapter 4. Disk I/O performance monitoring tools
119
tty:
tin
0.0
Disks:
hdisk3
hdisk2
hdisk0
hdisk1
cd0
hdisk4
tout
603.5
% tm_act
16.0
16.0
91.8
21.9
0.0
0.0
avg-cpu:
Kbps
2809.0
2868.8
8419.0
2820.9
0.0
0.0
% user
91.5
tps
117.7
122.7
263.3
117.7
0.0
0.0
% sys
8.5
Kb_read
2816
2876
0
2828
0
0
% idle
0.0
% iowait
0.0
Kb_wrtn
0
0
8440
0
0
0
This example shows the output of an iostat command run that is updated every
second (interval=1) and generated only two reports (count = 2).
Each report is a combination of a TTY and CPU utilization report and a disk
utilization report. This example shows a system with five hard disks
(hdisk0–hdisk4) and one CD-ROM drive. The first report shows the summary
statistics since system startup, providing the collective summary of I/O
operations on each drive. From the previous example, you can determine that
hdisk1 has been the most actively used drive.
The second report provided is the actual drive usage during a one second
interval.
During the report, there was a copy command started to provide disk I/O activity.
4.2.1 Historical disk I/O
In AIX 5L Version 5.1 and later, the system does not collect a history of disk
activity by default, as some system resources are consumed for this operation.
The system administrator has to decide whether to activate the disk I/O history or
not.
If the disk I/O history is disabled, the iostat command displays a message
similar to the following:
# iostat 1 1
tty:
tin
0.0
tout
avg-cpu: % user
% sys
% idle
41.5
61.2
0.1
38.8
" Disk history since boot not available. "
% iowait
0.0
Collecting disk I/O history is an AIX operating system setting that can be enabled
or disabled in SMIT using smit chgsys. Figure 4-2 on page 121 shows the
corresponding SMIT screen.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure 4-2 SMIT screen for changing characteristics of operating system
When the historical disk I/O is activated, ignore the first report if you are looking
for real-time behavior of your system.
4.2.2 Using disk I/O pacing
Disk-I/O pacing is intended to prevent programs that generate very large
amounts of output from saturating the system's I/O facilities and causing the
response times of less-demanding programs to deteriorate. Disk-I/O pacing
enforces per-segment (which effectively means per-file) high and low water
marks on the sum of all pending I/Os. When a process tries to write to a file that
already has high water mark pending writes, the process is put to sleep until
enough I/Os have completed to make the number of pending writes less than or
equal to the low water mark. The logic of I/O-request handling does not change.
The output from high-volume processes is slowed down somewhat.
The high and low water marks are set with the SMIT command by selecting
System Environments -> Change/Show Characteristics of Operating
System, as in Figure 4-3 on page 120, and then entering the number of pages
for the high and low water marks. The default value for the high and low water
marks is 0, which disables pacing. Changes to the maxpout and minpout values
take effect immediately and remain in place until they are explicitly changed.
Chapter 4. Disk I/O performance monitoring tools
121
Figure 4-3 The smitty chgsys fastpath to set high and low water marks
The effect of pacing on performance can be demonstrated with an experiment
that consists of starting a vi editor session on a new file while another process is
copying a 64 MB file with the cp command. The file is copied from hdisk1 to
hdisk0 and the vi executable program is located on hdisk0. For the vi session to
start, it must page itself in as well as perform a few other I/Os, which it does
randomly one page at a time. This takes about 50 physical I/Os, which can be
completed in 0.71 seconds on a slow machine when there is no contention for
the disk. With the high water mark set to the default of 0, the logical writes from
the cp command run ahead of the physical writes, and a large queue builds up.
Each I/O started by the vi session must wait its turn in the queue before the next
I/O can be issued, and thus the vi command is not able to complete its needed
I/O until after the cp command finishes. Table 4-2 shows the elapsed seconds for
cp execution and vi initialization with different pacing parameters.
Table 4-2 I/O pacing parameters effect on the cp and vi commands
122
High water mark
Low water mark
cp (sec)
vi (sec)
0
0
50
vi not done
0
0
50
vi finished after cp
9
6
77
2.7
17
8
64
3.4
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
High water mark
Low water mark
cp (sec)
vi (sec)
17
12
58
3.6
33
16
55
4.9
33
24
52
9.0
It is important to notice that the cp duration is always longer when pacing is set.
Pacing sacrifices some throughput on I/O-intensive programs to improve the
response time of other programs. The challenge for a system administrator is to
choose settings that result in a throughput/response-time trade-off that is
consistent with the organization's priorities.
The high and low water marks were chosen by trial and error, based on our
knowledge of the I/O path. Choosing them is not straightforward because of the
combination of write-behind and asynchronous writes. High water marks of (4 *
n) + 1, where n is a positive integer, work particularly well because of the
following interaction:
 The write-behind feature sends the previous four pages to disk when a logical
write occurs to the first byte of the fifth page.
 If the pacing high water mark were a multiple of 4 (for example, 8), a process
would hit the high water mark when it requested a write that extended into the
ninth page. It would then be put to sleep before the write-behind algorithm
had an opportunity to detect that the fourth dirty page is complete and the four
pages were ready to be written.
 The process would then sleep with four full pages of output until its
outstanding writes fell below the pacing low water mark.
 If, on the other hand, the high water mark had been set to 9, write-behind
would get to schedule the four pages for output before the process was
suspended.
One limitation of pacing is that it does not offer as much control when a process
writes buffers larger than 4 KB. When a write is sent to the VMM and the high
water mark has not been met, the VMM performs start I/Os on all pages in the
buffer, even if that results in exceeding the high water mark. Pacing works well
on the cp command because the cp command writes 4 KB at a time; but if the cp
command wrote larger buffers, the times shown in Table 4-2 on page 122 for
starting the vi session would increase.
Disk-I/O pacing is a tuning parameter that can improve interactive response time
in some situations where foreground or background programs that write large
volumes of data are interfering with foreground requests. If not used properly,
however, it can reduce throughput excessively. The settings in the previous table
Chapter 4. Disk I/O performance monitoring tools
123
are a good place to start, but some experimenting will be needed to find the best
settings for your workload. For the newer systems, view these numbers as the
minimum starting point.
Programs whose presence in a workload may make imposition of disk-I/O pacing
necessary include:
 Programs that generate large amounts of output algorithmically, and thus are
not constrained by the time required to read input. Some such programs may
need pacing on comparatively fast processors and not need it on
comparatively slow processors.
 Programs that write large, possibly somewhat modified, files that have been
read in their entirety shortly before writing begins (by a previous command,
for example).
 Filters, such as the tar command, that read a file and write it out again with
little processing. The need for pacing can be exacerbated if the input is being
read from a faster disk drive than the output is being written to.
Setting automatic reboot
Set the server to automatically reboot after a system crash with the SMIT
command by selecting System Environments -> Change/Show
Characteristics of Operating System, as in Figure 4-4 on page 123.
Figure 4-4 The smitty chgsys fastpath to set automatic reboot
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
4.2.3 TTY and CPU utilization report
The first report section displayed by the iostat command contains the TTY and
CPU utilization report.
The following columns are displayed and their meanings provided:
tin
Shows the total characters per second read by all TTY devices
tout
Indicates the total characters per second written to all TTY devices
% user
Shows the percentage of CPU utilization that occurred while
executing at the user level (application)
% sys
Shows the percentage of CPU utilization that occurred while
executing at the system level (kernel)
% idle
Shows the percentage of time that the CPU or CPUs were idle while
the system did not have an outstanding disk I/O request
% iowait
Shows the percentage of time that the CPU or CPUs was idle during
which the system had an outstanding disk I/O request
The TTY information columns, tin and tout, show the number of characters read
and written by all TTY devices. This includes both real and pseudo TTY devices.
Real TTY devices are those connected to an asynchronous port, such as serial
terminals, modems, FAXes, and so on. Pseudo TTY devices are telnet
sessions and xterm (or other X-based terminal emulators, such as dtterm and
aixterm).
Since the processing of character I/O consumes CPU resources, it is important
to monitor the relation between increased TTY activity and CPU utilization. If
such a relationship exists, the TTY devices, along with the applications using
these TTY devices, should be analyzed. For example, a FAX application could
be improved by enhancing the speed of the TTY port parameters so that a file
transfer would become faster and more efficient.
The CPU statistics columns % user, % sys, % idle, and % iowait provide
information about the CPU usage. The same information is also reported in the
vmstat command output in the columns us, sy, id, and wa.
In general, a high % iowait indicates that the system has a memory shortage due
to paging or an inefficient I/O subsystem configuration. Understanding the I/O
bottleneck and improving the efficiency of the I/O subsystem requires more data
than iostat can provide.
On a system that shows 0% iowait when running the iostat command, there still
might be an I/O bottleneck if the I/O to the disks is running at full capacity, as this
will not show up in the % iowait column.
Chapter 4. Disk I/O performance monitoring tools
125
When the iostat command report shows that a CPU-bound situation does not
exist with a high % idle and a % iowait time greater than 25 percent, this might
point to an I/O or disk-bound situation.
The following is an example extracted from an iostat command report:
...
tty:
Disks:
hdisk3
hdisk2
hdisk0
hdisk1
cd0
hdisk4
tin
0.0
tout
223.5
% tm_act
2.7
2.8
0.0
2.1
0.0
99.1
avg-cpu:
Kbps
163.2
170.8
0.0
175.6
0.0
715.6
% user
0.2
tps
20.4
21.9
0.0
17.3
0.0
125.0
% sys
4.2
Kb_read
1632
1708
0
1756
0
0
% idle
70.0
% iowait
25.5
Kb_wrtn
0
0
0
0
0
7156
The preceding example shows a high % iowait due to an I/O bottleneck on
hdisk4.
Depending on the actual system, a high % iowait time could also be caused by
excessive paging, due to a lack of real memory. It could also be due to
unbalanced disk load, fragmented data, or usage patterns.
For an unbalanced disk load, the same iostat report provides the necessary
information. But for information about file systems or logical volumes (which are
logical resources) you have to use an AIX-specific tool, such as filemon or
fileplace.
Alternatively, the iostat command can be used for determining that a
performance problem is related to the CPU. Although vmstat should be the
preferred tool for this analysis, in the absence of vmstat reports, iostat could be
used. A good indication of a CPU bound problem is when % iowait time is 0 and
the system is not idle (% idle = 0).
To investigate if a system does not have a memory problem, verify that the
physical volume that is used for swapping does not have an excessive load. Use
the lsps -a command to determine the physical volume of the swap area.
4.2.4 The iostat command on SMP systems
The calculation of I/O wait time on symmetrical multiprocessor (SMP) systems
has been modified to provide a more accurate accounting of CPU utilization in
commands such as vmstat and iostat.
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Prior to AIX Version 4.3.3, the calculation of I/O wait time on SMP systems could
result in inflated values (compared to uniprocessor (UP) systems). This was due
to a statistical anomaly of the way AIX counted CPU time. The vmstat and
iostat commands simply reported the CPU breakdown into the four categories
of usr/sys/wio/idle as tabulated within the kernel. At each clock interrupt on each
processor (100 times a second in AIX), a determination is made as to which of
the four categories to place the last 10 ms of time in. If the CPU is busy in user
mode at the time of the clock interrupt, usr gets the clock tick added into its
category. If the CPU is busy in kernel mode at the time of the clock interrupt, the
sys category gets the tick. If the CPU is not busy, a check is made to see if any
disk I/O is in progress. If any disk I/O is in progress, the wio category is
incremented. If no disk I/O is in progress and the CPU is not busy, then the idle
category gets the tick. Notice in the prior discussion that it does not matter which
processor starts the I/O. This fact leads to higher wio times on SMP systems
compared to UP systems in some situations.
Since AIX Version 4.3.3, the I/O wait time is no longer inflated; all CPUs are no
longer attributed wait time when a disk is busy and the CPU is idle. The decision
is based on whether a thread is awaiting an I/O on the CPU being measured.
This method can report accurate wio times when just a few threads are doing I/O
and the system is otherwise idle.
4.2.5 Disk utilization report
Any potential disk I/O performance problem should be analyzed with the iostat
command first. To only report the disk I/O, use the iostat command -d flag. In
addition, the disk statistics can be limited to the selected disks by listing the
physical volume names.
The iostat disk utilization report displays the following columns:
Disks
Shows the names of the physical volumes. They are either disk
or CD-ROM, followed by a number. By default, all drives are
displayed unless the drives are specified in the command line.
% tm_act
Indicates the percentage of time the physical disk was active. A
drive is active during data transfer and command processing,
such as seeking a new location. An increase in the disk active
time percentage implies a performance decrease and response
time increase. In general, when the utilization exceeds 40
percent, processes are waiting longer than necessary for I/O to
complete, because most UNIX processes sleep while waiting for
their I/O requests to complete.
Kbps
Indicates the amount of data transferred (read or write) to the
drive in KB per second. This is the sum of Kb_read plus Kb_wrtn,
divided by the seconds in the reporting interval.
Chapter 4. Disk I/O performance monitoring tools
127
tps
Indicates the number of transfers per second that were issued to
the physical disk. A transfer is an I/O request at the device driver
level to the physical disk. Multiple logical requests can be
combined into a single I/O request to the disk. A transfer is of
indeterminate size.
Kb_read
Displays the total data (in KB) read from the physical volume
during the measured interval.
Kb_wrtn
Displays the amount of data (in KB) written to the physical
volume during the measured interval.
When analyzing the drive utilization report and using the different data columns
just described, it is important to notice the patterns and relationships between the
data types.
There is normally a relationship between disk utilization %tm_act and data
transfer rate tps. If the disk busy rate %tm_act is high, then the tps rate should
also be high. However, if you get a high disk busy rate and a low disk transfer
rate, you may have either a fragmented logical volume, file system, or individual
file. Generally, you do need to be concerned about high disk busy when a disk is
being used by a single AIX process (for example, a batch job). For example, if an
application reads/writes sequentially, you should expect a high disk transfer rate
(tps) and a high disk busy rate (%tm_act).
Kb_read and Kb_wrtn can confirm an understanding of an application’s
read/write behavior. However, they provide no information on the data access
patterns.
An average physical volume utilization greater than 25 percent across all disks
indicates an I/O bottleneck. The general conclusion of performance problems on
disk, logical volume, and file system is that the more drives you have on your
system, the better the disk I/O performance.
However, there is a limit to the amount of data that can be handled by the SCSI
adapter; hence, the SCSI adapter could become a bottleneck. Especially on
RS/6000 systems with SCSI-1 and SCSI-2 adapters, this could become an
issue. To determine if a SCSI adapter is saturated, summarize all the KB/s
values for disks located on the same adapter and compare the sum with the
SCSI adapter throughput. In general, use 70 percent of the SCSI standard
throughput rate. Examples of different SCSI types and their throughput is
provided in the following:
 SCSI-1 throughput rate of 3.5 MB/s (70 percent of 5 MB/s)
 SCSI-2 throughput rate of 7 MB/s (70 percent of 10 MB/s)
 Ultra SCSI throughput rate of 28 MB/s (70 percent of 40 MB/s)
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 Ultra2 SCSI throughput rate of 56 MB/s (70 percent of 80 MB/s)
If a saturated adapter is discovered, solve the problem by moving disks to other,
less-used adapters already in the system or add an additional SCSI adapter.
For more information about improving disk I/O, see product documentation.
Note: As with the vmstat command, iostat can only give a first indication
about a performance bottleneck. The system administrator will have to use
more in-depth analysis tools such as filemon to identify the source of the
slowdown.
4.3 The lockstat command
The lockstat command displays lock-contention statistics on SMP systems.
The AIX kernel locks generated on the systems can be verified and possible
contentions identified.
Note: Before lockstat can be used, you must create, as root, a new boot
image with the -L option to enable lock instrumentation:
# bosboot -a -d /dev/hdiskx -L
Where x is the number of the bootdisk.
The lockstat command generates a report for each kernel lock that meets all
specified conditions. When no conditions are specified, the default values are
used.
The syntax of the lockstat command is as follows:
lockstat [ -a ] [ -c LockCount ] [ -b BlockRatio ] [ -n CheckCount ]
[ -p LockRate ] [ -t MaxLocks ] [ interval [ count ] ]
The commonly used flags of the lockstat command are provided in Table 4-3.
Table 4-3 Commonly used flags of the lockstat command
Flag
Description
-c LockCount
Specifies how many times a lock must be requested during an
interval in order to be displayed. A lock request is a lock
operation, which in some cases cannot be satisfied
immediately. All lock requests are counted. The default is 200.
Chapter 4. Disk I/O performance monitoring tools
129
Flag
Description
-b BlockRatio
Specifies a block ratio. When a lock request is not satisfied, it is
said to be blocked. A lock must have a block ratio that is higher
than BlockRatio to appear in the list. The default of BlockRatio
is 5 percent.
-n CheckCount
Specifies the number of locks that are to be checked. The
lockstat command sorts locks according to lock activity. This
parameter determines how many of the most active locks will be
subject to further checking. Limiting the number of locks that are
checked maximizes system performance, particularly if
lockstat is executed in intervals. The default value is 40.
-p LockRate
Specifies a percentage of the activity of the most-requested lock
in the kernel. Only locks that are more active than this will be
listed. The default value is 2, which means that the only locks
listed are those requested at least 2 percent as often as the
most active lock.
-t MaxLocks
Specifies the maximum number of locks to be displayed. The
default is 10.
If the lockstat command is executed with no options, an output similar to the
following would be displayed.
# lockstat
Subsys
Name
Ocn
Ref/s
%Ref
%Block
%Sleep
----------------------------------------------------------------PFS
IRDWR_LOCK_CLASS
259
75356
37.49
9.44
0.21
PROC
PROC_INT_CLASS
1
12842
6.39
17.75
0.00
The lockstat command report contains the following data columns:
130
Subsys
The subsystem to which the lock belongs.
Name
The symbolic name of the lock class.
Ocn
The occurrence number of the lock in its class.
Ref/s
The reference rate, or number of lock requests per
second.
%Ref
The reference rate expressed as a percentage of all lock
requests.
%Block
The ratio of blocking lock requests to total lock requests.
A block occurs whenever the lock cannot be taken
immediately.
%Sleep
The percentage of lock requests that causes the calling
thread to sleep.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Some common subsystems are as follows:
PROC
Scheduler, dispatcher, or interrupt handlers
VMM
Pages, segment, and freelist
TCP
Sockets, NFS
PFS
inodes, icache
The name of the lock class defined in AIX can be found in the file
/usr/include/sys/lockname.h. Some common classes are:
TOD_LOCK_CLASS All interrupts that need the Time-of-Day (TOD) timer
PROC_INT_CLASS
Interrupts for processes
U_TIMER_CLASS
Per-process timer lock
The lockstat command can also be run in intervals similar to the iostat
command, as shown in the following example:
# lockstat 10 100
The first number passed in the command line specifies the amount of time in
seconds between each report. Each report contains statistics collected during
the interval since the previous report. If no interval is specified, the system
provides information covering an interval of one second and then exits. The
second number determines the number of reports generated. It can only be
specified if an interval is given.
Note: The lockstat command can be CPU intensive because there is
overhead involved with lock instrumentation. That is the reason why it is not
turned on by default. The overhead of enabling lock instrumentation is
typically three to five percent. Be aware that AIX trace buffers will fill up much
quicker when using this option because there are a lot of locks being used.
4.4 LVM performance analysis using the lslv command
There are various factors that affect logical volume (LV) performance; for
example, the allocation position on the disk or the mirroring options. To obtain
information about the logical volume, you can use the LVM lslv command,
which provides information on:
LV attributes
List of the current logical volume settings
LV allocation
Placement map of the allocation of blocks on the disk
LV fragmentation
Fragmentation of the LV blocks
Chapter 4. Disk I/O performance monitoring tools
131
4.4.1 Logical volume attributes
Use the lslv command with no flags to view logical volume attributes, as shown
in the following output:
# lslv mirrlv
LOGICAL VOLUME:
mirrlv
LV IDENTIFIER:
000bc6fd1202118f.3
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
2
LPs:
120
STALE PPs:
0
INTER-POLICY:
maximum
INTRA-POLICY:
inner middle
MOUNT POINT:
/u/mirrfs
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
stripevg
read/write
closed/syncd
on
16 megabyte(s)
parallel
240
relocatable
yes
32
None
The previous example shows the LV attributes of a logical volume mirrlv, which is
a mirrored logical volume located in the volume group stripevg.
For performance issues, the following attributes have to be taken into account:
 COPIES
Indicates the number of physical copies. If copies equal 1, then the LV is
un-mirrored. Values of 2 and 3 are used for mirrored LVs. The previous
example has a copy value of 2.
 INTER-POLICY
The inter-physical volume allocation policy specifies which policy should be
used for choosing physical devices to allocate the physical partitions of a
logical volume.
 INTRA-POLICY
The intra-physical volume allocation policy specifies which strategy should be
used for choosing physical partitions on a physical volume.
 MIRROR WRITE CONSISTENCY
The mirror write consistency (MWC) ensures data consistency among
mirrored copies of a logical volume during normal I/O processing. For every
write to a logical volume, the LVM generates a write request to every mirrored
copy. Mirror write consistency recovery should be performed for most
mirrored logical volumes.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 WRITE VERIFY
Specifies whether to verify all writes to the logical volume with a follow-up
read. This option enhances availability, but decreases performance.
 SHED-POLICY
Specifies one of the two types of scheduling policies used for logical volumes
with multiple copies, sequential or parallel.
 BB POLICY
Specifies whether to use Bad Block Relocation, which redirects I/O requests
from a bad disk block to a valid one.
 RELOCATABLE
Specifies whether to allow the relocation of the logical volume during volume
group reorganization.
 UPPER BOUND
Specifies the maximum number of physical volumes for allocation.
Mirroring
To enhance the availability of a logical volume, AIX supports data mirroring by
providing multiple copies of the logical volumes on different disks.
When using mirroring, the write scheduling policies are:
 The parallel policy
The parallel policy balances reads between the disks. On each read, the
system checks whether the primary is busy. If it is not busy, the read is
initiated on the primary. If the primary is busy, the system checks the
secondary. If it is not busy, the read is initiated on the secondary. If the
secondary is busy, the read is initiated on the copy with the least number of
outstanding I/Os. Writes are initiated concurrently.
 The parallel/sequential policy
The parallel/sequential policy always initiates reads on the primary copy.
Writes are initiated concurrently.
 The parallel/round-robin policy
The parallel/round robin policy is similar to the parallel policy except that
instead of always checking the primary copy first, it alternates between the
copies. This results in equal utilization for reads even when there is never
more than one I/O outstanding at a time. Writes are initiated concurrently.
Chapter 4. Disk I/O performance monitoring tools
133
 The sequential policy
The sequential policy results in all reads being issued to the primary copy.
Writes happen serially, first to the primary disk; only when that is completed is
the second write initiated to the secondary disk.
The parallel write scheduling policy provides the best performance and is the
preferred option when creating the mirrored LV.
In general, the following recommendations provide the highest LVM availability:
 Use three logical partition copies (mirror twice) and include at least three
physical volumes.
 Write verify should be switched on.
 Inter-disk policy should be set to minimum, which sets the mirroring copies
equal to the number of physical volumes.
 Disk allocation policy should be set to strict, which establishes that no LP
copies are on the same disk.
 The copies on the physical volumes should be attached to separate busses,
adapters, and power supplies.
Providing the highest availability, however, can have a negative impact on LVM
performance; therefore, some of the settings may need to be altered depending
on your requirements.
Intra policy
The five LVM intra-allocation policies are: Inner edge, inner middle, center, outer
middle, outer edge. The corresponding intra-disk positions’ allocation policies are
illustrated in Figure 4-5 on page 135.
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Figure 4-5 LVM intra-disk positions
In general, the performance of the intra-disk policies is as follows:
 The center allocation policy has the fastest average seek times on disks with
< 4 GB of size. On larger disks, the outer edge has the fastest seek times.
 The outer middle and inner middle allocation policies provide reasonable
average seek times. This is the default setting when creating a new logical
volume.
 The outer edge (on disks < 4 GB) and inner edge policies have the slowest
average seek times.
Inter policy
The possible inter-disk allocation policies are the MINIMUM and MAXIMUM. The
MINIMUM inter-disk policy assigns the physical partitions to the logical volume
on the same disk or to as few disks as possible. The MINIMUM policy provides
the best availability.
The MAXIMUM inter-disk allocation policy allocates the physical partitions of the
logical volume on as many disks as possible. The MAXIMUM policy provides the
best performance.
For non-mirrored LVs, the MINIMUM policy indicates that one physical volume
should contain all the physical partitions of this logical volume. If the allocation
program must use two or more physical volumes, it uses the minimum number
possible.
For mirrored LVs, the MINIMUM policy indicates that as many physical volumes
as there are copies should be used. Otherwise, the minimum number of physical
volumes possible is used to hold all the physical partitions.
Chapter 4. Disk I/O performance monitoring tools
135
Striping
Striping is a technique for spreading the data in a logical volume across several
disk drives in such a way that the I/O capacity of the disk drives can be used in
parallel to access data on the logical volume. The primary objective of striping is
very high-performance reading and writing of large sequential files, but there are
also benefits for random access. Figure 4-6 gives a simple example. When a
striped LV is created, as many disks as possible should be used. Since AIX
Version 4.3.3, mirroring of striped LVs is supported; therefore, the old conclusion
that striping does not provide availability due to the lack of mirroring is no longer
valid.
Disk Adapter
First Logical
Partition
Stripe Unit 1
Stripe Unit 2
Stripe Unit 3
Stripe Unit 4
Stripe Unit 5
Stripe Unit 6
First Stripe
Second Stripe
Stripe Unit n
Stripe Unit n+1
Stripe Unit n+2
...
Stripe Unit n+3
Stripe Unit n+4
Stripe Unit n+5
...
First
Physical
Volume
...
...
Third
Physical
Volume
Second
Physical
Volume
Second Logical
Partition
Figure 4-6 Striping a logical volume
When a striped logical volume is defined, then two additional LV attributes are
displayed by the lslv command:
STRIPE WIDTH
The number of stripes.
STRIPE SIZE
The fixed size of each stripe block. Stripe size can be any
power of 2 from 4 KB to 128 KB, but it is often set to 64
KB to get the highest levels of sequential I/O throughput.
Following is an example of a striped logical volume:
# lslv testlv
LOGICAL VOLUME:
LV IDENTIFIER:
read/write
VG STATE:
136
testlv
VOLUME GROUP:
rootvg
00015f8f00004c00000000efd92f4f69.13 PERMISSION:
active/complete
LV STATE:
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
closed/syncd
TYPE:
jfs
WRITE VERIFY:
MAX LPs:
512
PP SIZE:
COPIES:
1
SCHED POLICY:
LPs:
32
PPs:
STALE PPs:
0
BB POLICY:
INTER-POLICY:
maximum
RELOCATABLE:
INTRA-POLICY:
middle
UPPER BOUND:
MOUNT POINT:
N/A
LABEL:
MIRROR WRITE CONSISTENCY: on/ACTIVE
EACH LP COPY ON A SEPARATE PV ?: yes (superstrict)
STRIPE WIDTH:
2
STRIPE SIZE:
8K
off
16 megabyte(s)
striped
32
relocatable
no
2
None
RAID
Disk arrays are groups of disk drives that act like one disk as far as the operating
system is concerned and which provide better availability or performance
characteristics than the individual drives operating alone. Depending on the
particular type of array that is used, it is possible to optimize availability or
performance or to select a compromise between both. A summary of the RAID
levels is provided in Table 4-4.
Table 4-4 RAID levels
RAID
levels
Common name
Description
I/O request rate
0
Disk striping
Data distributed across
the disks in the array.
No redundant
information provided.
Very high for both
read and write
1
Mirroring
All data replicated on N
separate disks. N is
most commonly 2.
Up to N times that of
a single disk for read,
less than a single
disk for write
3
Parallel transfer disks
with parity
Each data sector is
subdivided and
distributed across all
data disks. Redundant
information is normally
stored on a dedicated
parity disk.
Similar to twice that
of a single disk
Chapter 4. Disk I/O performance monitoring tools
137
RAID
levels
Common name
Description
I/O request rate
5
RAID 5
Data sectors are
distributed as with disk
striping; redundant
information is
interspersed with user
data.
Similar to disk
striping for read;
generally lower than
single disk for write
4.4.2 Logical volume fragmentation
To check a logical volume for possible fragmentation, use the lslv -l command,
as shown in the following example:
# lslv -l mirrlv
mirrlv:/u/mirrfs
PV
hdisk2
hdisk1
COPIES
120:000:000
120:000:000
IN BAND
90%
69%
DISTRIBUTION
000:000:000:108:012
000:000:000:083:037
This example uses the same LV mirrlv as in the last section.
The PV column indicates that the physical volume uses two disks (hdisk1 and
hdisk2).
The COPIES column indicates that the total number of logical partitions (LP) is
120, and since it is a mirrored LV, both disks have the same amount of physical
partitions (PPs) allocated (240 in total).
The IN BAND column indicates the level of intra-allocation policy as a
percentage. If the LVM cannot meet the intra-policy requirement, it chooses the
best alternative. In the above example, the intra-policy was inner middle, but
only 69 percent on hdisk1 and 90 percent on hdisk2 could follow this allocation
request.
The DISTRIBUTION column shows how the physical partitions are allocated in
each section of the intra policy, as shown in the following relationship:
(outer edge) : (outer middle) : (center) : (inner middle) : (inner edge)
In this example, hdisk1 has allocated 83 PPs on the requested inner middle and
37 on the outer edge. Disk hdisk2 allocates the intra policy request better, hence
the higher IN BAND level.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
4.4.3 Logical volume allocation
To see the logical volume allocation of placement on the physical volume, use
the following command:
# lslv -p hdisk1 mirrlv
hdisk1:mirrlv:/u/mirrfs
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
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FREE
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
81-90
91-100
101-109
USED
USED
USED
USED
USED
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USED
USED
USED
USED
USED
USED
USED
USED
110-119
120-129
130-139
140-149
150-159
160-169
170-179
180-189
190-199
200-209
210-217
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
USED
USED
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
218-227
228-237
238-247
248-257
258-267
268-277
278-287
288-297
298-307
308-317
318-325
USED
USED
USED
0006
0016
0026
USED
USED
USED
0007
0017
0027
USED
USED
USED
0008
0018
0028
USED
USED
USED
0009
0019
0029
USED
USED
USED
0010
0020
0030
USED
USED
0001
0011
0021
0031
USED
USED
0002
0012
0022
0032
USED
USED
0003
0013
0023
0033
USED
USED
0004
0014
0024
0034
USED
USED
0005
0015
0025
0035
326-335
336-345
346-355
356-365
366-375
376-385
Chapter 4. Disk I/O performance monitoring tools
139
0036
0046
0056
0066
0076
0037
0047
0057
0067
0077
0038
0048
0058
0068
0078
0039
0049
0059
0069
0079
0040
0050
0060
0070
0080
0041
0051
0061
0071
0081
0042
0052
0062
0072
0082
0043
0053
0063
0073
0083
0044
0054
0064
0074
0045
0055
0065
0075
386-395
396-405
406-415
416-425
426-433
0084
0094
0104
0114
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0085
0095
0105
0115
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0086
0096
0106
0116
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0087
0097
0107
0117
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0088
0098
0108
0118
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0089
0099
0109
0119
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0090
0100
0110
0120
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0091
0101
0111
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0092
0102
0112
FREE
FREE
FREE
FREE
FREE
FREE
FREE
FREE
0093
0103
0113
FREE
FREE
FREE
FREE
FREE
FREE
FREE
434-443
444-453
454-463
464-473
474-483
484-493
494-503
504-513
514-523
524-533
534-542
The output displays five sections that represent: Outer edge, outer middle,
center, inner middle, and inner edge.
Each physical partition is marked with either a number or a keyword, which is
described in the following:
Number
A number indicates the logical partition number of the LV.
USED
This keyword indicates that the physical partition at this location is
used by another logical volume.
FREE
This keyword indicates that this physical partition is not used by any
logical volume. Logical volume fragmentation occurs if logical
partitions are not contiguous across the disk.
STALE
Although not present in the previous example, the STALE keyword
indicates a physical partition that cannot be used.
This example shows that the one copy of mirrlv located on hdisk1 is allocated
contiguously. The logical partitions (LPs) from 01–83 are allocated in the inner
middle section, while the LPs 84–120 are allocated in the inner edge section.
When logical volumes are deleted, the physical partitions are freed, and this
enables the space for either new logical volumes or the possibility of reorganizing
the logical volumes, so that the LV fragmentation is limited. The LVM command
reorgvg can reorganize logical volumes so that they comply with the intra-disk
policies. By using reorgvg and providing both the volume group and the name of
the logical volume, the highest priority is given to the listed volume group when
performing the reorganization. During the reorganization, the volume group is
locked and cannot be used.
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4.4.4 Highest LVM performance
The following general recommendations can be used for creating logical volumes
with high performance demands. However, keep in mind that when a logical
volume is tuned for better performance, the availability may be impacted.
 No mirroring, which means the number of copies equals one (1).
 If mirroring is required then:
– Write scheduling policy set to parallel.
– Allocation policy set to strict, which means each copy is on separate
physical volumes.
 Write verification set to no.
 Mirror write consistency (MWC) set to off.
 Intra policies:
– Center: For hot logical volumes
– Middle: For moderate logical volumes
– Edge: For cold logical volumes
 Inter-disk allocation policy set to maximum, which mean that read/write
operations are spread among physical volumes.
Additional performance improvement can be gained by creating a striped logical
volume.
4.5 LVM and file system monitoring
To provide a more complete analysis of file system performance, AIX Version 4.3
provides a monitoring command, filemon. This provides information about a
specific application or system I/O activity, assisting the problem determination
process for performance tuning.
4.5.1 The filemon command
The filemon command monitors and presents trace data on the following four
levels of file system utilization:
Logical file system
The monitored operations include all read, write, open,
and lseek system calls, which may or may not result in
actual physical I/O, depending on whether the files are
already buffered in memory. I/O statistics are kept on a
per-file basis.
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141
Virtual memory system At this level, operations (that is, paging) between
segments and their images on disk are monitored. I/O
statistics are kept on a per-segment basis.
Logical volumes
I/O statistics are kept on a per-logical-volume basis.
Physical volumes
At this level, physical resource utilizations are
obtained. I/O statistics are kept on a
per-physical-volume basis.
Using the filemon command
The filemon command is based on the AIX trace facility to monitor I/O activity
during a certain time interval. Because of this, filemon can be run only by root,
and filemon cannot be executed in parallel with other trace-based commands,
such as tprof and netpmon.
Tracing is started implicitly by the filemon command, but the trace can be
controlled by the normal trace utilities: trcstop, trcoff, and trcon.
When tracing is stopped with trcstop, filemon writes a report either to stdout or
to a specified file.
To specify the levels of data collected on all the layers, or on specific layers, use
the -O layer option. The default is to collect data on the VM, LVM, and physical
layers. Both summary and detailed reports are both generated.
Note: The filemon command will only collect data for those files opened after
filemon was started, unless you specify the -u flag.
The following command sequence provides a simple example of filemon in
action:
# filemon -o /tmp/filemonLF.out -O lf
Enter the "trcstop" command to complete filemon processing
# dd count=2048 if=/dev/zero of=/u/mirrfs/testMirrorFile
2048+0 records in.
2048+0 records out.
# dd count=2048 of=/dev/null if=/u/mirrfs/testMirrorFile
2048+0 records in.
2048+0 records out.
# trcstop
[filemon: Reporting started]
[filemon: Reporting completed]
[filemon: 10.666 secs in measured interval]
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# ls -l filemonLF.out
-rw-r--r-1 root
#
system
2627 Jul 07 12:51 filemonLF.out
The filemon command is started with the flag -O, specifying that only the logical
file system (lf) data is to be monitored. This example uses two dd commands to
write to a file and read from a file. The special devices /dev/zero and /dev/null are
used to get clean read/write figures and make the reports more transparent. The
output report of the filemon command in this example is placed in a dedicated
file using the -o flag. The default is to write the report to the standard output.
4.5.2 Report analysis
The reports generated by filemon are dependent on the output level flag -O. The
possible values for the output levels are:
lf
Logical file level
lv
Logical volume level
pv
Physical volume level
vm
Virtual memory level
The default value of -O is all. However, if -O is specified without a level, then lv,
pv, and vm are the default.
The following section explains the filemon output reports using the examples
from 4.5.1, “The filemon command” on page 141.
Logical file level report
The logical file level report, as shown in the following example, provides two
sections, the Most Active Files Report, for information on the active files during
the trace, and the Detailed File Stats Report, for detailed statistics on the
individual files.
# cat /tmp/filemonLF.out
Fri Jul 7 12:51:38 2000
System: AIX server1 Node: 4 Machine: 000BC6FD4C00
Cpu utilization:
100.0%
Most Active Files
-----------------------------------------------------------------------#MBs #opns
#rds
#wrs file
volume:inode
-----------------------------------------------------------------------2.0
2
2048
2048 testMirrorFile
/dev/mirrlv:17
1.0
1
2048
0 zero
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143
1.0
0.0
0.0
0.0
1
3
2
1
0
6
2
2
2048
0
0
0
null
ksh.cat
dd.cat
cmdtrace.cat
/dev/hd2:23079
/dev/hd2:22970
/dev/hd2:22947
-----------------------------------------------------------------------Detailed File Stats
-----------------------------------------------------------------------FILE: /u/mirrfs/testMirrorFile volume: /dev/mirrlv
opens:
2
total bytes xfrd:
2097152
reads:
2048
(0 errs)
read sizes (bytes):
avg
512.0 min
512 max
read times (msec):
avg
0.003 min
0.000 max
writes:
2048
(0 errs)
write sizes (bytes): avg
512.0 min
512 max
write times (msec):
avg
0.028 min
0.012 max
lseeks:
1
FILE: /dev/zero
opens:
1
total bytes xfrd:
1048576
reads:
2048
(0 errs)
read sizes (bytes):
avg
512.0 min
512 max
read times (msec):
avg
0.007 min
0.006 max
FILE: /dev/null
opens:
total bytes xfrd:
writes:
write sizes (bytes):
write times (msec):
1
1048576
2048
(0 errs)
avg
512.0 min
avg
0.001 min
512 max
0.000 max
inode: 17
512 sdev
0.084 sdev
0.0
0.005
512 sdev
0.443 sdev
0.0
0.044
512 sdev
0.076 sdev
0.0
0.003
512 sdev
0.023 sdev
0.0
0.002
FILE: /usr/lib/nls/msg/en_US/ksh.cat volume: /dev/hd2 (/usr) inode: 23079
opens:
3
total bytes xfrd:
24576
reads:
6
(0 errs)
read sizes (bytes):
avg 4096.0 min
4096 max
4096 sdev
0.0
read times (msec):
avg
0.033 min
0.000 max
0.085 sdev
0.036
lseeks:
15
FILE: /usr/lib/nls/msg/en_US/dd.cat volume: /dev/hd2 (/usr) inode: 22970
opens:
2
total bytes xfrd:
8192
reads:
2
(0 errs)
read sizes (bytes):
avg 4096.0 min
4096 max
4096 sdev
0.0
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
read times (msec):
avg
4.380 min
0.000 max
8.760
lseeks:
10
FILE: /usr/lib/nls/msg/en_US/cmdtrace.cat volume: /dev/hd2
22947
opens:
1
total bytes xfrd:
8192
reads:
2
(0 errs)
read sizes (bytes):
avg 4096.0 min
4096 max
4096
read times (msec):
avg
0.000 min
0.000 max
0.000
lseeks:
8
sdev
4.380
(/usr)
sdev
sdev
inode:
0.0
0.000
The Most Active Files Report contains summary information of the most
frequently used files during the monitoring period, defined in the following list.
#MBS
Total number of megabytes transferred to and from the
file. The rows are sorted by this field, in decreasing order.
#opns
Number of times the file was opened during the
measurement period.
#rds
Number of read system calls made against the file.
#wrs
Number of write system calls made against the file.
file
Name of the file (full path name is in the detailed report).
volume:inode
Name of volume that contains the file, and the file's inode
number. This field can be used to associate a file with its
corresponding persistent segment, shown in the virtual
memory I/O reports. This field may be blank (for example,
for temporary files created and deleted during execution).
The filemon example shows that the file testMirrorFile is the most active, with
the 1 MB read and 1 MB write operations. Notice the read and write operations
are made in 512 bytes units. This shows that the dd command used a 512-byte
block size. The zero and null files do not have inodes because they are not
connected to any file system, but are special device files.
From the filemon file-level report, it is very easy to see which files are generating
the most I/O demand.
The Detailed File Stats Report provides information about every active file with
the following details:
FILE
Name of the file. The full path name is given, if possible.
volume
Name of the logical volume/file system containing the file.
inode
inode number for the file within its file system.
opens
Number of times the file was opened while monitored.
total bytes xfrd
Total number of bytes read/written to/from the file.
Chapter 4. Disk I/O performance monitoring tools
145
reads
Number of read calls against the file.
read sizes (bytes)
The read transfer-size statistics (avg, min, max, and
sdev), in bytes.
read times (msec)
The read response-time statistics (avg, min, max, and
sdev), in milliseconds.
writes
Number of write calls against the file.
write sizes (bytes)
The write transfer-size statistics.
write times (msec)
The write response-time statistics.
seeks
Number of lseek subroutine calls.
The detailed file level report from the previous filemon example is focusing on
the file testMirrorFile. Here the read and write size of 512 bytes is even more
evident. As it is the only read/write size used, the standard deviation (sdev)
becomes 0. The read/write time is an interesting value in the detailed file
statistics report. These can show, among other things, how the file system cache
is performing.
Logical volume level report
The logical volume level report provides two sections: The Most Active Logical
Volumes report and the Detailed Logical Volume Stats report.
The logical volume level report, provided by the following command, was
generated from the same example in“Using the filemon command” on page 142,
except the output level -O lv flags are used:
# filemon -o /tmp/filemonLF.out -O lv
The following is an excerpt from the logical volume level report:
...
Most Active Logical Volumes
-----------------------------------------------------------------------util #rblk #wblk
KB/s volume
description
-----------------------------------------------------------------------0.07
0
2016
64.5 /dev/mirrlv
/u/mirrfs
0.00
0
8
0.3 /dev/loglv00
jfslog
0.00
8
0
0.3 /dev/hd2
/usr
...
The headings are:
146
util
Utilization of the volume (fraction of time busy). The rows
are sorted by this field, in decreasing order.
#rblk
Number of 512-byte blocks read from the volume.
#wblk
Number of 512-byte blocks written to the volume.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
KB/sec
Total transfer throughput in Kilobytes per second.
volume
Name of volume.
description
Contents of volume: Either a file system name or logical
volume type (paging, jfslog, boot, or sysdump). Also
indicates if the file system is fragmented or compressed.
This section of the logical volume level report shows clearly that the mirrlv is the
most utilized LV. The report shows the transfer throughput of 64.5 KB/s for the
mirrlv and its file system mirrfs. Notice also some activity on the loglv00, which is
the jfslog for mirrfs.
Physical volume level report
The physical volume level report provides two sections: The Most Active
Physical Volumes report and the Detailed Physical Volume Stats report.
The physical volume level report, provided by the following command, was
generated with the same example as in “Using the filemon command” on
page 142, except the output level -O pv was used:
# filemon -o /tmp/filemonLF.out -O pv
The following is an extraction of the physical volume level report:
...
Most Active Physical Volumes
-----------------------------------------------------------------------util #rblk #wblk
KB/s volume
description
-----------------------------------------------------------------------0.07
0
2096
66.4 /dev/hdisk1
N/A
0.07
0
2080
65.9 /dev/hdisk2
N/A
0.02
0
305
9.7 /dev/hdisk0
N/A
...
The headings are:
util
Utilization of the volume (fraction of time busy). The rows
are sorted by this field, in decreasing order.
#rblk
Number of 512-byte blocks read from the volume.
#wblk
Number of 512-byte blocks written to the volume.
KB/s
Total volume throughput in Kilobytes per second.
volume
Name of volume.
description
Type of volume, for example, 9.1 GB disk or CD-ROM
SCSI.
Chapter 4. Disk I/O performance monitoring tools
147
The physical volume level report of the filemon example shows almost equal
activity of the two PVs, hdisk1 and hdisk2, because they are the mirrored copies
of mirrlv.
Notice that hdisk1 has a slightly higher write block size than hdisk2 (and due to
that, a slightly higher throughput). This is because the jfslog loglv00 is located on
hdisk1.
Virtual memory level report
The virtual memory level report provides two sections: The Most Active
Segments report and the Detailed VM Segment Stats report.
The virtual memory level report, provided by the following command, was
generated with the same example as in“Using the filemon command” on
page 142, except the output level -O vm was used:
# filemon -o /tmp/filemonLF.out -O vm
The following is an excerpt of a virtual memory level report:
...
Most Active Segments
-----------------------------------------------------------------------#MBs #rpgs #wpgs segid segtype
volume:inode
-----------------------------------------------------------------------1.0
0
252
c473 page table
0.0
0
1
fefe log
...
The headings are:
148
#MBs
Total number of megabytes transferred to and from the
segment. The rows are sorted by this field, in decreasing
order.
#rpgs
Number of 4096-byte pages read into segment from disk
(that is, page-in).
#wpgs
Number of 4096-byte pages written from segment to disk
(page-out).
segid
Internal ID of segment.
segtype
Type of segment: Working segment, persistent segment
(local file), client segment (remote file), page table
segment, system segment, or special persistent
segments containing file system data (log, root directory,
.inode, .inodemap, .inodex, .inodexmap, .indirect,
.diskmap).
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
volume:inode
For persistent segments, the name of the volume that
contains the associated file, and the file's inode number.
This field can be used to associate a persistent segment
with its corresponding file, shown in the file I/O reports.
This field is blank for non-persistent segments.
In this filemon example, the virtual memory level report does not contain any
important information; it is merely mentioned for the completeness of the filemon
reporting capabilities.
4.5.3 Typical AIX system behavior
When using the filemon command for performance analysis, the following issues
should be kept in mind. The items listed are recommendations extracted from the
documentation RS/6000 Performance Tools in Focus, SG24-4989.
Frequently accessed files:
 The /etc/inittab file is always very active. Daemons specified in /etc/inittab are
checked regularly to determine whether they are required to be respawned.
 The /etc/passwd file is also very active, because file and directory access
permissions is checked.
Disk access:
 A long seek time increases I/O response time and decreases performance.
 If the majority of the reads and writes require seeks, you may have
fragmented files or overly active file systems on the same physical disk.
 If the number of reads and writes approaches the number of sequences,
physical disk access is more random than sequential. Sequences are strings
of pages that are read (paged in) or written (paged out) consecutively. The
sequence length is the length, in pages, of the sequences. A random file
access can also involve many seeks. In this case, you cannot distinguish from
the filemon output if the file access is random or if the file is fragmented. If
you have to further investigate with the fileplace command, see 4.9.2, “The
fileplace command” on page 164, for more information.
Solutions to disk-bound problems:
 If large, I/O-intensive background jobs are interfering with interactive
response time, you may want to activate I/O pacing.
 If it appears that a small number of files are being read over and over again,
you should consider whether additional real memory would allow those files
to be buffered more effectively.
Chapter 4. Disk I/O performance monitoring tools
149
 If the iostat command indicates that your workload I/O activity is not evenly
distributed among the system disk drives, and the utilization of one or more
disk drives is often 40-50 percent or more, consider reorganizing your file
systems.
 If the workload’s access pattern is predominantly random, you may want to
consider adding disks and distributing the randomly accessed files across
more drives.
 If the workload’s access pattern is predominantly sequential and involves
multiple disk drives, you may want to consider adding one or more disk
adapters. It may also be appropriate to consider building a striped logical
volume to accommodate large, performance-critical sequential files.
4.6 File system performance
These are some factors that affect file system performance.
 Dynamic allocation of resources may cause:
– Logically contiguous files to be fragmented
– Logically contiguous LVs to be fragmented
– File blocks to be scattered
 Effects when files are accessed from disk:
– Sequential access no longer sequential
– Random access affected
– Access time dominated by longer seek time
Once the file is in memory, these effects diminish.
Before going into analyzing the file system performance, an overview of how the
AIX JFS is organized is in order.
4.6.1 AIX file system organization
In a journaled file system (JFS), files are stored in blocks of contiguous bytes.
The default block size, also referred to as fragmentation size in AIX, is 4096
bytes (4 KB). The JFS inode contains an information structure of the file together
with an array of eight pointers to data blocks. A file that is less than 32 KB is
referenced directly from the inode.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
A larger file uses a 4 KB block, referred to as an indirect block, for the addressing
of up to 1024 data blocks. Using an indirect block, the file size of 4 MB (1024 x 4
KB) is possible.
For files larger than 4 MB, a second block, the double indirect block, is used. The
double indirect block points to 512 indirect blocks, providing the possible
addressing of 2 GB files (512 x 1024 x 4 KB). Figure 4-7 illustrates the
addressing using double indirection.
Figure 4-7 JFS organization
Since the introduction of AIX Version 4.2, support for even larger files has been
added by defining a new type of JFS, the bigfile file system. In the bigfile file
system, the double indirect are using references to 128 KB blocks rather than 4
KB blocks. However, the first indirect block still points to a 4 KB block, so that the
large blocks are only used when the file size is above 4 MB. This provides a new
maximum file size of just under 64 GB.
Chapter 4. Disk I/O performance monitoring tools
151
4.6.2 Enhanced journaled file system (JFS2)
Enhanced journaled file system supports the entire set of file system semantics.
The file system uses database journaling techniques to maintain its structural
consistency. This prevents damage to the file system when the file system is
halted abnormally. Each JFS2 resides on a separate logical volume. The
operating system mounts JFS2 during initialization. This multiple file system
configuration is useful for system management functions such as backup,
restore, and repair. It isolates a part of the file tree to allow system administrators
to work on a particular part of the file tree.
The enhanced journaled file system (JFS2) supports multiple file system block
sizes of 512, 1024, 2048, and 4096. Smaller block sizes minimize wasted disk
space by more efficiently storing the data in a file or directory's partial logical
blocks. Smaller block sizes also result in additional operational overhead.
The block size for a JFS2 is specified during its creation. Different file systems
can have different block sizes, but only one block size can be used within a single
file system.
 Variable number of inodes for enhanced journaled file system:
JFS2 allocates inodes as needed. Therefore, the number of inodes available
is limited by the size of the file system itself.
 Specifying file system block size:
File system block size is specified during the file system's creation with the
crfs and mkfs commands or by using the SMIT. The decision of file system
block size should be based on the projected size of files contained by the file
system.
 Identifying file system block size:
The file system block size value can be identified through the lsfs command
or the System Management Interface Tool (SMIT). For application programs,
the statfs subroutine can be used to identify the file system block size.
 Compatibility and migration:
The enhanced journaled file system (JFS2) is a new file system and is not
compatible with any previous version of this operating system.
 Device driver limitations:
A device driver must provide disk block addressability that is the same or
smaller than the file system block size.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 Performance costs:
Although file systems that use block sizes smaller than 4096 bytes as their
allocation unit might require substantially less disk space than those using the
default allocation unit of 4096 bytes, the use of smaller block sizes can incur
performance degradation.
 Increased allocation activity:
Because disk space is allocated in smaller units for a file system with a block
size other than 4096 bytes, allocation activity can occur more often when files
or directories are repeatedly extended in size. For example, a write operation
that extends the size of a zero-length file by 512 bytes results in the allocation
of one block to the file, assuming a block size of 512 bytes. If the file size is
extended further by another write of 512 bytes, an additional block must be
allocated to the file. Applying this example to a file system with 4096-byte
blocks, disk space allocation occurs only once, as part of the first write
operation. No additional allocation activity is performed as part of the second
write operation since the initial 4096-byte block allocation is large enough to
hold the data added by the second write operation.
 Increased block allocation map size:
More virtual memory and file system disk space might be required to hold
block allocation maps for file systems with a block size smaller than 4096
bytes. Blocks serve as the basic unit of disk space allocation, and the
allocation state of each block within a file system is recorded in the file system
block allocation map.
 Understanding enhanced journaled file system size limitations:
The maximum size for an enhanced journaled file system is architecturally
limited to 4 Petabytes. inodes are dynamically allocated by JFS2, so you do
not need to consider how many inodes you may need when creating a JFS2
file system. You need to consider the size of the file system log.
 Enhanced journaled file system log size issues:
In most instances, multiple journaled file systems use a common log
configured to be 4 MB in size. When file systems exceed 2 GB or when the
total amount of file system space using a single log exceeds 2 GB, the default
log size might not be sufficient. In either case, scale log sizes upward as the
file system size increases. The JFS log is limited to a maximum size of
256 MB.
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 JFS2 file space allocation:
File space allocation is the method by which data is apportioned physical
storage space in the operating system. The kernel allocates disk space to a
file or directory in the form of logical blocks. Logical block refers to the division
of a file or directory contents into 512, 1024, 2048, or 4096 byte units. When a
JFS2 file system is created the logical block size is specified to be one of 512,
1024, 2048, or 4096 bytes. Logical blocks are not tangible entities; however,
the data in a logical block consumes physical storage space on the disk. Each
file or directory consists of 0 or more logical blocks.
 Full and partial logical blocks:
A file or directory may contain full or partial logical blocks. A full logical block
contains 512, 1024, 2048, or 4096 bytes of data, depending on the file system
block size specified when the JFS2 file system was created. Partial logical
blocks occur when the last logical block of a file or directory contains less than
the file system block size of data.
For example, a JFS2 file system with a logical block size of 4096 with a file of
8192 bytes is two logical blocks. The first 4096 bytes reside in the first logical
block and the following 4096 bytes reside in the second logical block.
Likewise, a file of 4608 bytes consists of two logical blocks. However, the last
logical block is a partial logical block containing the last 512 bytes of the file's
data. Only the last logical block of a file can be a partial logical block.
 JFS2 file space allocation:
The default block size is 4096 bytes. You can specify smaller block sizes with
the mkfs command during a file system's creation. Allowable fragment sizes
are 512, 1024, 2048, and 4096 bytes. You can use only one block’s size in a
file system.
The kernel allocates disk space so that only the last file system block of data
receives a partial block allocation. As the partial block grows beyond the limits
of its current allocation, additional blocks are allocated.
Block reallocation also occurs if data is added to logical blocks that represent
file holes. A file hole is an empty logical block located prior to the last logical
block that stores data. (File holes do not occur within directories.) These
empty logical blocks are not allocated blocks. However, as data is added to
file holes, allocation occurs. Each logical block that was not previously
allocated disk space is allocated a file system block of space.
Additional block allocation is not required if existing data in the middle of a file
or directory is overwritten. The logical block containing the existing data has
already been allocated file system blocks.
JFS tries to maintain contiguous allocation of a file or directory's logical blocks
on the disk. Maintaining contiguous allocation lessens seek time because the
data for a file or directory can be accessed sequentially and found on the
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same area of the disk. The disk space required for contiguous allocation may
not be available if it has already been written to by another file or directory.
The file system uses a bitmap called the block allocation map to record the
status of every block in the file system. When the file system needs to allocate
a new block, it refers to the block allocation map to identify which blocks are
available. A block can only be allocated to a single file or directory at a time.
 Extents:
An extent is a sequence of contiguous file system blocks allocated to a JFS2
object as a unit. Large extents may span multiple allocation groups.
Every JFS2 object is represented by an inode. inodes contain the expected
object-specific information such as time stamps and file type (regular verses
directory and others.) They also contain a B+ tree to record the allocation of
extents.
A file is allocated in sequences of extents. An extent is a contiguous
variable-length sequence of file system blocks allocated as a unit. An extent
may span multiple allocation groups. These extents are indexed in a B+ tree.
There are two values needed to define an extent, the length and the address.
The length is measured in units of the file system block size. 24-bit value
represents the length of an extent, so an extent can range in size from 1 to
224 -1 file system blocks. Therefore the size of the maximum extent depends
on the file system block size. The address is the address of the first block of
the extent. The address is also in units of file system blocks. It is the block
offset from the beginning of the file system.
An extent-based file system combined with user-specified file system block
size allows JFS2 to not have separate support for internal fragmentation. The
user can configure the file system with a small file system block size (such as
512 bytes) to minimize internal fragmentation for file systems with large
numbers of small-sized files.
In general, the allocation policy for JFS2 tries to maximize contiguous
allocation by allowing a minimum number of extents, with each extent as
large and contiguous as possible. This allows for larger I/O transfer resulting
in improved performance.
 Data fragmentation:
JFS2 supports fragmented file systems. Fragmentation saves disk space by
allowing a logical block to be stored on the disk in units or fragments smaller
than the full block size of 4096 bytes. In a fragmented file system, only the
last logical block of files no larger than 32 KB is stored in this manner, so that
fragmented support is only beneficial for file systems containing numerous
small files.
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The use of fragments increases the potential for fragmentation of disk free
space. Fragments allocated to a logical block must be contiguous on the disk.
A file system experiencing free space fragmentation might have difficulty
locating enough contiguous fragments for a logical block allocation, even
though the total number of free fragments may exceed the logical block
requirements. The JFS2 alleviates free space fragmentation by providing the
defragfs program, which defragments a file system by increasing the amount
of contiguous free space. The disk space savings gained from fragments can
be substantial, while the problem of free space fragmentation remains
manageable.
4.6.3 Journeled file system (JFS) log management
JFS logs enable rapid and clean recovery of file systems if a system goes down.
If an application is doing synchronous I/O or is creating and removing many files
in a short amount of time, there might be a lot of I/O going to the JFS log logical
volume. If both the JFS log logical volume and the file system logical volume are
on the same disk, this could cause an I/O bottleneck. We recommend migrating
the JFS log device to another physical disk. It is also a good idea to create
multiple JFS logs for a volume and assign them to specific file systems,
preferably on fast-write cache devices, as these can provide for much better
performance for log logical volumes (JFS logs or database logs).
You can have multiple log devices in a volume group. However, a log for a file
system must be in the same volume group as that of the file system. A log logical
volume or file system logical volume can be moved to another disk using the
migratepv command, even while the system is running and in use. Remember to
place the log logical volume on a physical volume different from your most active
file system logical volume, as this will increase parallel resource usage.
Following is an example of how to create a new JFS log.
1. Create a new JFS log logical volume, as in the following example:
# mklv -t jfslog -y JFSlog testvg 1 hdisk2
JFSlog
Or use the smitty mklv fastpath command shown in Figure 4-8 on page 157.
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Figure 4-8 The smitty mklv add a logical volume dialog
2. Format the log, as in the following example:
# /usr/sbin/logform /dev/JFSlog
logform: destroy /dev/JFSlog (y)?y
3. Modify /etc/filesystems and the logical volume control block (LVCB), as in the
following example:
# chfs -a log=/dev/JFSlog /testfilesystem
4. Unmount and then mount the file system. The mount option nointegrity may
enhance local file system performance for certain write-intensive applications.
This optimization eliminates writes to the JFS log. Note that the enhanced
performance is achieved at the expense of metadata integrity. Therefore, use
this option with extreme caution because a system crash can make a file
system mounted with this option unrecoverable. The following is an example
of the mount command:
# mount -o nointegrity /testfilesystem
4.6.4 The fileplace command
The use of files and file systems, depending on the application, can be very
dynamic and can, over time, result in fragmentations that have impact on the file
system performance, which influences the application performance.
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Access to fragmented files may yield a large number of seeks and longer I/O
response time. At some point, the system administrator may decide to
reorganize the placement of files within the logical volume to reduce
fragmentation and gain a more even distribution.
The fileplace command can assist in this task by displaying the placement of
blocks in a file within a logical volume or within one or more physical volumes.
The fileplace command expects an argument containing the name of the file to
examine, as shown in the following example:
# fileplace -iv sixMB
File: sixMB Size: 6291456 bytes Vol: /dev/restlv
Blk Size: 4096 Frag Size: 4096 Nfrags: 1536
Compress: no
Inode: 21 Mode: -rw-r--r-- Owner: root Group: sys
DOUBLE INDIRECT BLOCK: 77000
INDIRECT BLOCKS: 75321 77001
Logical Fragment
---------------0149576-0149583
0075322-0075773
0149584-0150147
0077002-0077513
8
452
564
512
frags
frags
frags
frags
32768
1851392
2310144
2097152
Bytes,
Bytes,
Bytes,
Bytes,
0.5%
29.4%
36.7%
33.3%
1536 frags over space of 74826 frags: space efficiency = 2.1%
4 fragments out of 1536 possible: sequentiality = 99.8%
This example displays the logical fragmentation of a large file (6 MB). The
general information displayed by fileplace is:
File
Name of the file.
Size
File size in bytes.
Vol
Name of the logical volume of the file system.
Blk Size
Physical block size 4 KB.
Frag Size
Fragment size; typically also 4 KB, but can be specified to
values 512, 1 KB, or 2 KB at file system creation time.
Nfrags
The total amount of fragments used by the file.
Compress
Compression of file system. The default is no.
Inode
The inode reference number.
Mode/Owner/Group General UNIX file system level inode information.
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This file has, due to its size, both indirect blocks (75321, 77001) and a double
indirect block (7700). This information is listed using the fileplace -i flag.
The first column under Logical Fragment shows the logical block numbers where
the different parts of the file are. The next column shows the number of
fragments that are contiguous and the amount of bytes in these contiguous
fragments. The last number is the percentage of the block range compared to the
total size.
Finally, the values for space efficiency and space sequentially are calculated
when the fileplace -v flag is used. Higher space efficiency means files are less
fragmented and will probably provide better sequential file access. Higher
sequentially indicates that the files are more contiguously allocated, and this will
probably be better for sequential file access.
Using fileplace -p, the physical block numbers and physical volume or
volumes are shown.
The following is an example using fileplace on a mirrored logical volume:
# fileplace
-p /u/mirrfs/t5
File: /u/mirrfs/t5 Size: 504320 bytes Vol: /dev/mirrlv
Blk Size: 4096 Frag Size: 4096 Nfrags: 124
Compress: no
Physical Addresses (mirror copy 1)
Fragment
------------------------------------------------0320104-0320111 hdisk1
8 frags
0004168-0004175
0319242-0319305 hdisk1
64 frags
0003306-0003369
0319310-0319361 hdisk1
52 frags
0003374-0003425
Physical Addresses (mirror copy 2)
Fragment
------------------------------------------------0320104-0320111 hdisk2
8 frags
0004168-0004175
0319242-0319305 hdisk2
64 frags
0003306-0003369
0319310-0319361 hdisk2
52 frags
0003374-0003425
Logical
32768 Bytes,
6.5%
262144 Bytes,
51.6%
212992 Bytes,
41.9%
Logical
32768 Bytes,
6.5%
262144 Bytes,
51.6%
212992 Bytes,
41.9%
This example shows the physical addresses used for the file t5 on the logical
volume mirrlv. This file is physically located on both hdisk1 and hdisk2.
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The fileplace command will not display NFS remote files. If a remote file is
specified, the fileplace command returns an error message.
The fileplace command reads the file’s list of blocks directly from the logical
volume on disk. If the file is newly created, extended, or truncated, the
information may not be on disk yet. Use the sync command to flush the
information to the logical volume.
4.6.5 File system defragmentation
During the lifetime of a file system, a large number of files are created and
deleted. This leaves, over time, a large number of gaps of free blocks. This
fragmentation has a negative impact on the file system performance, as the
newly created files become highly fragmented.
There is a simple way of organizing the free gaps in the file system. The
defragfs command increases a file system's contiguous free space by
reorganizing allocations to be contiguous rather than scattered across the disk. It
does not increase the actual free space. The defragfs command is intended for
fragmented and compressed file systems. However, you can also use the
defragfs command to increase contiguous free space in non-fragmented file
systems.
Another simple way of reorganizing the file system is to recreate the file system
using a backup of the file system.
4.7 General recommendations for I/O performance
By using lslv, fileplace, filemon, and iostat, you can identify I/O, volume
group, and logical volume problems. The following are general recommendations
for how to achieve good LVM and file system performance and when to use the
tools described in this chapter.
4.7.1 Logical volume organization for highest performance
The following general recommendations pertain to logical volume organization.
 Allocate hot LVs to different PVs to reduce disk contention.
 Spread hot LVs across multiple PVs so that parallel access is possible.
 Place the hottest LVs in the center of PVs, the moderate LVs in the middle of
PVs, and the coldest LVs on edges of PVs so that the hottest logical volumes
have the fastest access time.
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 Mirroring can improve performance for read-intensive applications, but, as
writes need to be performed several times, can impact the performance of
other applications.
If mirroring is needed, set the scheduling policy to parallel and the allocation
policy to strict. Parallel scheduling policy will enable reading from the closest
disk, and strict allocation policy allocates each copy on separate PVs.
 Make the LV contiguous to reduce access time.
 Set inter policy to maximum. This will spread each logical volume across as
many physical volumes as possible, allowing reads and writes to be shared
among several physical volumes.
 Place frequently used logical volumes close together to reduce the seek time.
 Set write verify to no so that there is no follow-up read (similar to a parity
check) performed following a write.
4.7.2 Logical volume striping recommendations
The following are recommendations for logical volume striping.
 Spread the logical volume across as many physical volumes as possible.
 Use as many adapters as possible for the physical volumes.
 Create a separate volume group for striped logical volumes.
 Set a stripe-unit size of 64 KB.
 Set minpgahead to 2 (vmtune command).
 Set maxpgahead to 16 times the number of disk drives (vmtune command).
This causes page-ahead to be done in units of the stripe-unit size (64 KB)
times the number of disk drives, resulting in the reading of one stripe unit from
each disk drive for each read-ahead operation.
 Request I/Os for 64 KB times the number of disk drives. This is equal to the
maxpgahead value.
 Modify maxfree (vmtune command) to accommodate the change in
maxpgahead (maxfree = minfree + maxpgahead).
 Use 64-byte aligned I/O buffers. If the logical volume will occupy physical
drives that are connected to two or more disk adapters, the I/O buffers used
should be allocated on 64-byte boundaries. This avoids having the LVM
serialize the I/Os to the different disks. The following code would yield a
64-byte aligned buffer pointer:
char *buffer;
buffer = malloc(MAXBLKSIZE+64);
buffer = ((int)buffer + 64) & ~0x3f;
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 If the striped logical volumes are on raw logical volumes and writes larger
than 1.125 MB are being done to these striped raw logical volumes,
increasing the lvm_bufcnt parameter with the vmtune command might
increase throughput of the write activity.
 Also, it is not a good idea to mix striped and non-striped logical volumes in the
same physical volume. All physical volumes should be the same size within a
set of striped logical volumes.
 Limitations of striping:
– Mirroring with striping prior to AIX Version 4.3.3 is not possible. On AIX
4.3.3 or later, the mirroring of logical volume striping is possible using the
superstrict physical allocation policy.
– Disk striping is mostly effective for sequential disk I/Os. With randomly
accessed files, it is not as effective.
4.7.3 RAID recommendations
Select RAID 0 for applications that would benefit from the increased performance
capabilities of this RAID level, but, because no data redundancy is provided, do
not use RAID 0 for mission-critical applications that require high availability.
Select RAID 1 for applications where data availability is a key concern, and
which have high levels of write operations, such as transaction files, and where
cost is not a major concern.
Select RAID 3 for applications that process large blocks of data where write
performance is not the key factor, and where the reduced cost of RAID 3
compared to mirroring is important.
Select RAID 5 for applications that manipulate small amounts of data, such as
transaction processing applications. Since all the disk heads move
independently to satisfy multiple requests, this is appropriate for multi-user
applications. Also select RAID 5 as a good compromise between high
performance, high availability, and low cost.
4.7.4 File system related performance issues
The following are file system performance issues.
 Create an additional log logical volume to separate the log of the most active
file system from the default log. This will increase parallel resource usage.
 An lslv usage scenario:
Determine if hot file systems are better located on a physical drive or spread
across multiple physical drives.
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 Some filemon usage scenarios:
– Determine if hot files are local or remote.
– Determine if paging space dominates disk utilization.
– Look for heavy physical volume utilization. Determine if the type of drive
(SCSI-1, SCSI-2, tape, and so on) or SCSI adapter is causing a
bottleneck.
 Some fileplace usage scenarios:
– Determine if the application performs a lot of synchronous (non-cached)
file I/Os.
– Look for file fragmentation. Determine if the hot files are heavily
fragmented.
4.7.5 Paging space related disk performance issues
The following discusses paging space related disk performance issues.
 Never add more than one paging space on the same physical volume.
 Reorganize or add paging space to several physical volumes.
4.8 Overhead of using performance tools
As in any performance measurement on a system, each measurement
consumes some resources. This is referred to as the overhead of the
performance tools.
lslv
This command mainly uses CPU time.
filemon
This command can consume some CPU power. Use this tool with
discretion, and analyze the system performance while taking into
consideration the overhead involved in running the tool. In a
CPU-saturated environment with a high disk-output rate, filemon
slowed the writing program by about five percent.
fileplace Most variations of fileplace use fewer than 0.3 seconds of CPU
time.
iostat
The iostat command adds little overhead to the system. It uses
about 20 milliseconds of CPU time for each report generated.
Note that the previous computing time measurements are from an RS/6000
Model 320.
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4.9 Command summary
The following section provides a list of the key commands discussed in this
chapter.
4.9.1 The filemon command
The filemon command monitors the performance of the file system, and reports
the I/O activity on behalf of logical files, virtual memory segments, logical
volumes, and physical volumes. The command has the following syntax:
filemon [ -d ] [ -i file ] [ -o file] [ -O levels ] [ -P ] [ -T n] [ -u ] [-v ]
The commonly used flags are provided in Table 4-5.
Table 4-5 Commonly used flags of the filemon command
Flag
Description
-O levels
Monitors only the specified file system levels. Valid level
identifiers are: lf (logical file level), vm (virtual memory level), lv
(logical volume level), pv (physical volume level), and all (all is a short
for lf, vm, lv, pv). If no -O flag is specified, the vm, lv, and pv levels
are implied by default.
-o file
Name of the file where the output report is stored. If no flag is
specified, the output is displayed on the standard output.
-u
Reports on files that were opened prior to the start of the trace
daemon. The process ID (PID) and the file descriptor (FD) are
substituted for the file name.
4.9.2 The fileplace command
The fileplace command displays the placement of file blocks within logical or
physical volumes. The command has the following syntax and the flags are
provided in Table 4-6:
fileplace [ { -l | -p } [ -i ] [ -v ] ] File
Table 4-6 Commonly used flags of the fileplace command
164
Flag
Description
-l
Displays file placement in terms of logical volume fragments for the
logical volume containing the file. The -l and -p flags are mutually
exclusive.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-p
Displays file placement in terms of underlying physical volume, for the
physical volumes that contain the file. If the logical volume containing
the file is mirrored, the physical placement is displayed for each mirror
copy. The -l and -p flags are mutually exclusive.
-i
Displays the indirect blocks for the file, if any. The indirect blocks are
displayed in terms of either their logical or physical volume block
addresses, depending on whether the -l or -p flag is specified.
-v
Displays more information about the file and its placement, including
statistics on how widely the file is spread across the volume and the
degree of fragmentation in the volume. The statistics are expressed
in terms of either the logical or physical volume fragment numbers,
depending on whether the -l or -p flag is specified.
4.9.3 The lslv command
The lslv command displays information about a logical volume. The command
has the following syntax and the flags are provided in Table 4-7.
Display logical volume information:
lslv [ -L ] [ -l|-m ] [ -nPhysicalVolume ] LogicalVolume
Display logical volume allocation map:
lslv [ -L ] [ -nPhysicalVolume ] -pPhysicalVolume [ LogicalVolume ]
Table 4-7 Commonly used flags of the lslv command
Flag
Description
-l
Lists the fields for each physical volume in the logical volume.
-p
PhysicalVolum
e
Displays the logical volume allocation map for the PhysicalVolume
variable. If you use the LogicalVolume parameter, any partition
allocated to that logical volume is listed by logical partition number.
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4.10 Quiz
The following assessment questions help verify your understanding of the topics
discussed in this chapter.
1. While a user is compiling a C program, vmstat 120 10 is run to determine the
cause of a performance problem. Given the vmstat output as shown in the
exhibit indicates an I/O bottleneck, which of the following commands should
be run next to get more information about the problem?
/usr/bin/vmstat 120 10
kthr memory
page
faults
cpu
------ ------------- -------------------- -----------------------------------r b avm
fre
re pi po fr sr cy in
sy
cs
us sy id
0 1 59903 542
0 0 0 0 0 0 451
912
478
43 11 15
0 2 59904 550
0 0 0 0 0 0 521
1436 650
23 19 4
0 3 59950 538
0 0 0 0 0 0 344
649
249
7 7
6
0 2 59899 578
0 0 0 0 0 0 467
1829 500
12 14 4
0 2 59882 589
0 0 0 0 0 0 600
1292 705
6 8
3
0 3 59882 420
0 0 0 0 0 0 452
952
372
11 8
1
0 2 59954 420
0 0 0 0 0 0 537
1979 573
13 5
10
0 2 59954 423
0 0 0 0 0 0 618
1413 686
15 9
6
0 3 59954 420
0 0 0 0 0 0 551
938
634
4 2
2
0 2 59954 422
0 0 0 0 0 0 460
1376 496
14 2
4
A.
lsps
B.
tprof
wa
31
50
80
70
61
80
72
70
92
80
C. iostat
D.
vmtune
2. Which of the following commands should be used to show the percentage of
time that the CPU(s) is idle waiting for pending system I/Os to complete?
A.
tprof
B.
pstat
C. iostat
D.
filemon
3. Which of the following commands should be used to monitor disk utilization
during the time a system is experiencing a disk I/O performance problem?
A.
pstat
B.
iostat
C. vmstat
D.
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4. Which of the following utilities should be used to determine which disk or set
of disks is experiencing contention on a SCSI bus?
A.
lspv
B.
iostat
C. lsdev
D.
vmstat
5. Which of the following metrics provided by the iostat report is used to initially
determine if a system is I/O bound?
A.
tin and tout
B.
% user and % sys
C. % iowait and % tm_act
D.
Kb_read and Kb_wrtn
6. If the filemon command is invoked, which of the following indicates how to
stop the command so that the filemon reports can be generated?
A.
Run trcstop.
B.
Run filemon -u.
C. Perform a kill -15 on the filemon PID.
D.
Perform a kill -SIGSTOP on the filemon PID.
7. Which of the following tools should be used to examine the details of a file’s
indirect inode, assuming it uses indirect inodes?
A.
df
B.
istat
C. filemon
D.
fileplace
8. Which of the following tools will report how much of a logical volume is
following its intra-policy request?
A.
df -k
B.
lslv -l
C. lsvg -l
D.
fileplace
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167
9. Which of the following is true of the fileplace command?
A.
A file can be placed in a specific location.
B.
The fragment distribution on a specified file is shown.
C. Fragmentation is removed by rearranging file fragments.
D.
The distribution of all the files on a specified disk is shown.
10.Which of the following logical volume placement policies most likely provides
the best performance for a logical volume that has Mirror Write Consistency
Check turned on?
A.
INTRA-POLICY set to edge
B.
INTRA-POLICY set to center
C. INTRA-POLICY set to middle
D.
INTRA-POLICY set to inner middle
11.There is a system where all rootvg logical volumes reside on the same disk
(hdisk0), with the exception of the boot logical volume, which resides on
another disk (hdisk1).
# filemon -O lv -o filemon.out;sleep 60;trcstop; cat filemon.out
Most Active Logical Volumes
----------------------------------------------------------------------util #rblk
#wblk
KB/s volume
description
----------------------------------------------------------------------0.84 105792
149280
177.1 /dev/hd9var /var
0.32 0
16800
11.9 /dev/hd8
jfslog
0.01 4608
0
3.2
/dev/hd4
/
0.02 55296
0
5.9
/dev/hd2
/usr
0.01 2976
0
2.1
/dev/hd1
/home
Using the filemon output as shown in the preceding exhibit, the workload
across the disks should be balanced by:
A.
Moving the /var file system from hdisk0 to hdisk1
B.
Moving the hd5 logical volume from hdisk1 to hdisk0
C. Creating a separate JFS log for the / (root) file system on hdisk1
D.
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Creating a separate JFS log for the /var file system on hdisk1
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
12.If the percentage of RAM occupied by file pages falls below minperm, the
page replacement algorithm steals:
A.
File pages only
B.
Computational only
C. Both file and computational pages
D.
Persistent memory
13.An SMP system is running slowly and vmstat reflects high CPU idle time.
Which of the following commands should be used to investigate contention?
A.
vmtune
B.
schedtune
C. filemon
D.
lockstat
14.There is a mount option called nointegrity that bypasses the use of JFS
logging. All of the following statements are true except:
A.
This option can provide better I/O performance, but can sacrifice a rapid
and clean recovery of file systems.
B.
This option enables fsck to be done automatically at bootup of the file
system should the system go down without a clean shutdown.
C. This option can reduce I/O bottlenecks caused by a busy logical volume,
especially if the system is creating and removing many files in a short
amount of time.
D.
Fast-write cache devices can provide better performance for log logical
volumes and can be a better option than the nointegrity.
15.An application is causing a response time issue. Which of the following can
be used to determine the problem?
A.
filemon
B.
fileplace
C. rmss
D.
netstat
Chapter 4. Disk I/O performance monitoring tools
169
4.10.1 Answers
The following are the preferred answers to the questions provided in this section.
1. C
2. C
3. B
4. B
5. C
6. A
7. D
8. B
9. B
10.A
11.A
12.C
13.D
14.B
15.A
4.11 Exercises
The following exercises provide sample topics for self study. They will help
ensure comprehension of this chapter.
1. On a test system, with preferably two spare disks, create a testvg volume
group. Create test logical volumes with the different parameters discussed in
this chapter: Mirrored LV, intra-disk policy, inter-disk policy, strict policy, and
striping.
2. Use the lslv command on the LVs created above and verify LV attributes, LV
fragmentation, and LV allocation.
3. Perform a filemon trace on your test system using the following command
sequence:
# filemon -u -O lf,lv,pv -o /tmp/filemon.out ; sleep 30; tracestop
Identify the most active files, logical volume, and disk drive.
4. On an existing file system, create a large file. Verify its fragmentation as well
as space efficiency and sequence with the fileplace command.
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5
Chapter 5.
Network performance tools
The following topics are discussed in this chapter:
 Network performance problems overview
 Network monitoring tools
 Network tuning tools
This chapter looks at network performance problems. It describes network
examination and problem-solving procedures.
© Copyright IBM Corp. 2002. All rights reserved.
171
5.1 Overview
The recommended network performance tools to use first are the ping and the
netstat commands. Usually, they provide you with enough information to
discover your problems; if not, this chapter provides you with more insight into
the network performance topic.
To understand the performance characteristics of the network subsystem in AIX,
you must first understand some of the underlying architecture. Figure 5-1 on
page 174 shows the path of data from an application on one system to another
application on a remote system. The following discussion matches the diagram:
 As an application writes to a socket, the data is copied from the user space
into the socket send buffer in the kernel space. Depending on the amount of
data being copied into the socket send buffer, the socket puts the data into
either mbufs or clusters. The size of the buffers in virtual memory that are
used by the input is limited by the values:
– udp_sendspace
– tcp_sendspace
 Once the data is copied into the socket send buffer, the socket layer calls the
transport layer (either TCP or UDP), passing it a pointer to the linked list of
mbufs (an mbuf chain).
 If the size of the data is larger than the maximum transfer unit (MTU) of the
LAN, one of the following is generally done:
– TCP breaks the output into segments that comply with the MTU limit.
– UDP leaves the breaking up of the output to the IP layer.
 If IP receives a packet larger than the MTU of the interface, it fragments the
packet and sends the fragments to the receiving system, which reassembles
them into the original packet.
 When the interface layer receives a packet from IP, it attaches the link-layer
header information to the beginning of the packet and calls the device driver
write routine.
 At the device-driver layer, the mbuf chain containing the packet is enqueued
on the transmit queue. The maximum total number of output buffers that can
be queued is controlled by the system parameter tx_que_size.
 Arriving packets are placed on the device driver's receive queue, and pass
through the interface layer to IP. The maximum total number of input buffers
that can be queued is controlled by the system parameter rx_que_size.
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 If IP in the receiving system determines that IP in the sending system has
fragmented a block of data, it coalesces the fragments into their original form
and passes the data to TCP or UDP. If one of the fragments is lost in
transmission, the incomplete packet is ultimately discarded by the receiver.
The length of time IP waits for a missing fragment is controlled by the ipfragttl
parameter.
– TCP reassembles the original segments and places the input in the socket
receive buffer.
– UDP simply passes the input on to the socket receive buffer.
The maximum size of IP's queue of packets received from the network
interface is controlled by the ipqmaxlen parameter, which is set and displayed
with the no command. If the size of the input queue reaches this number,
subsequent packets are dropped.
 When the application makes a read request, the appropriate data is copied
from the socket receive buffer in kernel memory into the buffer in the
application's working segment.
Chapter 5. Network performance tools
173
Application
Application
write buffer
read buffer
copy to socket
buffer
copy to app.
buffer
socket layer
stream
socket send
buffer
mbuf
datagrams
datagrams
socket receive
buffer
stream
mbuf
TCP/UDP layer
MTU compliance
IP layer
MTU enforcement
Interface layer
transmit queue
device driver
mbufs
IP input queue
receive queue
mbufs
adapter/media
Figure 5-1 UDP/TCP/IP data flow
5.2 Adapter transmit and receive queue tuning
Most communication drivers provide a set of tunable parameters to control
transmit and receive resources. These parameters typically control the transmit
queue and receive queue limits, but may also control the number and size of
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buffers or other resources. To check queue size for the ent0 adapter, use the
lsattr command:
# lsattr -El ent0
busio
0x1000100
busintr
15
intr_priority 3
tx_que_size
64
rx_que_size
32
full_duplex
no
use_alt_addr no
alt_addr
0x000000000000
Bus I/O address
Bus interrupt level
Interrupt priority
TRANSMIT queue size
RECEIVE queue size
Full duplex
Enable ALTERNATE ETHERNET address
ALTERNATE ETHERNET address
False
False
False
True
True
True
True
True
To change queue size parameters, perform the following procedure.
Bring down the interface:
# ifconfig en0 detach
Change the value of the appropriate parameter:
# chdev -l ent0 -a tx_que_size=128
ent0 changed
Bring the interface back to the up state:
# ifconfig en0 up
To check if the queue’s size should be changed, run the netstat command or
adapter statistics utilities (entstat, tokstat, or others):
# netstat -v
ETHERNET STATISTICS (ent0) :
Device Type: IBM PCI Ethernet Adapter (22100020)
Hardware Address: 08:00:5a:fc:d2:e1
Elapsed Time: 0 days 0 hours 19 minutes 16 seconds
Transmit Statistics:
-------------------Packets: 19
Bytes: 1140
Interrupts: 0
Transmit Errors: 0
Packets Dropped: 0
Receive Statistics:
------------------Packets: 0
Bytes: 0
Interrupts: 0
Receive Errors: 0
Packets Dropped: 0
Bad Packets: 0
Max Packets on S/W Transmit Queue: 1
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0
Broadcast Packets: 19
Multicast Packets: 0
Broadcast Packets: 0
Multicast Packets: 0
Chapter 5. Network performance tools
175
....
Two parameters should be checked:
 Max Packets on S/W Transmit Queue. This is the maximum number of
outgoing packets ever queued to the software transmit queue. An indication
of an inadequate queue size is if the maximal transmits queued equals the
current queue size tx_que_size. This indicates that the queue was full at
some point.
 S/W Transmit Queue Overflow. The number of outgoing packets that have
overflowed the software transmit queue. A value other than zero indicates
that the same actions needed if the Max Packets on S/W Transmit Queue
reaches the tx_que_size should be taken. The transmit queue size has to be
increased.
Adapter statistics utilities are quite useful. For example, the entstat command
displays the statistics gathered by the specified Ethernet device driver. The user
can optionally specify that the device-specific statistics be displayed in addition
to the device-generic statistics. If no flags are specified, only the device-generic
statistics are displayed. In the following example, to display the Ethernet
device-generic statistics and the Ethernet device-specific statistics for ent0,
enter:
# entstat -d ent0
------------------------------------------------------------ETHERNET STATISTICS (ent0) :
Device Type: IBM 10/100 Mbps Ethernet PCI Adapter (23100020)
Hardware Address: 00:06:29:b9:1f:08
Elapsed Time: 1 days 1 hours 24 minutes 55 seconds
Transmit Statistics:
-------------------Packets: 443312
Bytes: 198577053
Interrupts: 2915
Transmit Errors: 0
Packets Dropped: 1
Receive Statistics:
------------------Packets: 979962
Bytes: 114525647
Interrupts: 828638
Receive Errors: 0
Packets Dropped: 0
Bad Packets: 0
Max Packets on S/W Transmit Queue: 24
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 1
5.3 Protocols tuning
The main goal in network performance tuning is to balance demands of users
against resource constraints to ensure acceptable network performance.
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You can do this with the following steps:
 Characterize workload, configuration, and bandwidth.
 Measure performance.
– Run tools, identify bottlenecks.
– Useful tools are netstat, tcpdump, and iptrace.
 Tune network parameters.
– Make adjustments.
– Useful tuning parameters are no, nfso, chdev, and ifconfig.
AIX allocates virtual memory for various TCP/IP networking tasks. The network
subsystem uses a memory management facility called an mbuf. Mbufs are
mostly used to store data for incoming and outbound network traffic. Having
mbuf pools of the right size can have a very positive effect on network
performance. Heavy network load can be a reason for low memory for the
system, but too little virtual memory for network use can cause packet dropping.
The dropped packet, on the other hand, can reduce the effective transmission
throughput because of retransmissions or time outs.
The AIX operating system offers the capability for run-time mbuf pool
configuration. There are a few system parameters that you can tune for this
purpose:
thewall
Kernel variable, controls the maximum amount of RAM (in
kilobytes) that the mbuf management facility can allocate
from the VMM.
tcp_sendspace
Kernel variable, sets default socket send buffer. It keeps
an application from overflowing the socket send buffer
and limits the number of mbufs used by an application.
The default value for tcp_sendspace is 16384.
tcp_recvspace
Kernel variable, used as the default socket receive buffer
size when an application opens a TCP socket. The default
value for tcp_recvspace is 16384.
udp_sendspace
Kernel variable, sets the limit for the amount of memory
that can be used by a single UDP socket for buffering
out-going data. If a UDP application fills this buffer space,
it must sleep until some of the data has passed on to the
next layer of the protocol stack. The default value for
udp_sendspace is 9216.
udp_recvspace
Kernel variable, sets the size limit of the receive space
buffer for any single UDP socket. The default value for
udp_recvspace is 41920.
Chapter 5. Network performance tools
177
rfc1323
If the value of this variable is non-zero, it allows the TCP
window size to be the maximum of 32 bits instead of 16
bits. What this means is that you can set tcp_recvspace
and tcp_sendspace to be greater than 64 KB.
sb_max
Kernel variable, controls the upper limit for any buffers.
ipqmaxlen
Kernel variable, controls length of the IP input queue. The
default is 100 packets long, which is sufficient for
single-network device systems. You may increase this
value for systems with multiple network devices. The
penalty for insufficient queue length is dropped packets.
ipforwarding
Specifies whether the kernel should forward packets. The
default value of 0 prevents forwarding of IP packets when
they are not for the local system. A value of 1 enables
forwarding. ipforwarding is a runtime attribute.
udp_pmtu_discover Enables or disables path MTU discovery for UDP
applications. A value of 0 disables the feature, while a
value of 1 enables it. This option is a runtime command.
tcp_pmtu_discover Enables or disables path MTU discovery for TCP
applications. A value of 0 disables the feature, while a
value of 1 enables it. This option is a runtime command.
The operating system supports a path MTU discovery algorithm enabled by
modifying udp_pmtu_discover and tcp_pmtu_discover with the no command.
These options automatically force the size of all packets to not exceed the path
MTU. When the path MTU has been discovered for a network route, a separate
host route is cloned for the path. These cloned host routes, as well as the path
MTU value for the route, can be displayed using the netstat -r command.
Route expiration is controlled by the route_expire option of the no command.
Note: The values of the tcp or udp_sendspace and tcp or udp_recvspace
variables must be less than or equal to the sb_max, so if you have reduced
sb_max from its default, or want to use buffers larger than that default, you
must also change the sb_max variable.
A network application that sends data in large bursts, such as a backup over the
network, can generate socket buffer overflows. Insufficient buffer space for TCP
sockets will merely limit throughput, but not inhibit proper operation. The TCP
window limits the amount of data pending to be acknowledged and effectively
limits the throughput of the sockets. The tcp_recvspace controls the TCP window
size, which cannot be bigger than the socket buffer space. To increase
performance of such an application, you have to remove the TCP window size
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limit by setting the parameter rfc1323 to 1 and increasing the tcp_sendspace and
tcp_recvspace values.
5.4 Network performance monitoring tools
This section describes the most common monitoring tools used to isolate
network performance problems.
5.4.1 The vmstat command
You should invoke network monitoring tools in order to get more statistics for
isolating a network bottleneck. When the vmstat command shows significant
amounts of idle time that does not fit the problem, the system may be network
bound. The following is a typical vmstat command report:
# vmstat 120 10
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 1 19331
824
0
0
0 0
0
0 636 1955 674 0 0 99 0
0 1 19803
996
0
0
0 0
0
0 533 7466 591 0 0 99 0
0 1 19974
860
0
0
0 0
0
0 822 4055 892 0 0 99 0
0 1 19815
860
0
0
0 0
0
0 535 4096 509 0 0 99 0
0 1 19816
855
0
0
0 0
0
0 577 4582 598 0 0 99 0
0 1 19816
737
0
0
0 0
0
0 602 2720 672 0 0 99 0
0 1 19895
724
0
0
0 0
0
0 616 3842 698 0 0 99 0
0 1 17147
724
0
0
0 0
0
0 649 6427 626 0 0 99 0
0 1 17065
720
0
0
0 0
0
0 516 3629 543 0 0 99 0
0 1 17163
720
0
0
0 0
0
0 614 9030 688 0 0 99 0
0 1 17343
720
0
0
0 0
0
0 420 8777 487 0 0 99 0
0 1 17579
712
0
0
0 0
0
0 466 2182 473 0 0 99 0
0 1 17647
712
0
0
0 0
0
0 497 3298 310 0 0 99 0
The disk I/O wait is in the wa column and the nondisk wait is in the id column.
Nondisk wait includes network I/O wait or terminal I/O wait. If there is no terminal
I/O wait, then the system is waiting for network I/O to complete. You should run
one of the network monitoring tools to find out the reason for the network I/O
wait.
The ping command
When you have connection problems, the first tool you should use is the ping
command. It is used for investigating basic point-to-point network connectivity
problems, answering questions about whether the remote host is attached to the
network, and whether the network between the hosts is reliable. Additionally,
ping can indicate whether a host name and IP address is consistent across
Chapter 5. Network performance tools
179
several machines. To check if the host server3 is alive, enter the following
command:
# ping server3
PING server3: (9.3.240.58): 56 data bytes
64 bytes from 9.3.240.58: icmp_seq=0 ttl=255 time=1 ms
64 bytes from 9.3.240.58: icmp_seq=1 ttl=255 time=0 ms
^C
----server3 PING Statistics---2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0/0/1 ms
This test checks round-trip times and packet loss statistics, as shown in the
previous example.
5.4.2 The traceroute command
If you cannot reach a host that is in a different network, you can check the
connection using the traceroute command. The traceroute output shows each
gateway that the packet traverses on its way to find the target host, and the delay
or network latency associated with that segment. If possible, examine the routing
tables of the last machine shown in the traceroute output to check if a route
exists to the destination from that host. The last machine shown is where the
routing is going astray.
# traceroute 9.3.240.56
traceroute to 9.3.240.56 (9.3.240.56), 30 hops max, 40 byte packets
1 server4e (10.47.1.1) 1 ms 1 ms 0 ms
2 server1 (9.3.240.56) 1 ms 1 ms 1 ms
If the connections are performing poorly, packet fragmentation may be a
problem. AIX Version 4.3 has a service that allows automatic path MTU
discovery. A fixed MTU size can also be set with the no command.
5.4.3 The netstat command
The most common network monitoring tool is netstat. The netstat command is
used to show the network status. It gives you an indication of the reliability of the
local network interface. Traditionally, it is used more for problem determination
than for performance measurement. It is useful in determining the amount of
traffic on the network, therefore ascertaining whether performance problems are
due to congestion.
There are various options to display:
 Active sockets
 Protocol statistics
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 Device driver information
 Network data structures
To display statistics recorded by the memory management routines, use the
netstat command with the -m flag. To enable more extensive statistics for
network memory services (for AIX Version 4.3.2 and later), you should set kernel
variable extendednetstats to 1 first, as shown in the following:
# no -o extendednetstats=1
# netstat -m
16 mbufs in use:
0 mbuf cluster pages in use
4 Kbytes allocated to mbufs
0 requests for mbufs denied
0 calls to protocol drain routines
Kernel malloc statistics:
******* CPU 0 *******
By size
inuse
32
97
64
124
128
111
256
152
512
32
1024
1
2048
1
4096
2
8192
2
16384
1
calls failed
102
0
805
0
923
0
41806
0
231
0
158
0
716
0
14
0
133
0
1
0
free
31
68
17
24
16
19
1
7
2
12
hiwat
640
320
160
384
40
20
10
120
10
24
By type
mbuf
mcluster
socket
pcb
routetbl
ifaddr
mblk
mblkdata
strhead
strqueue
strmodsw
strosr
strsyncq
streams
devbuf
kernel table
calls failed
41218
0
764
0
862
0
495
0
15
0
7
0
435
0
294
0
48
0
112
0
20
0
20
0
326
0
245
0
1
0
15
0
memuse
4096
0
18048
12480
1312
832
15104
16384
3232
9216
1280
0
2688
14976
256
45920
memmax
19712
8192
18688
12992
2080
832
15488
35840
4256
11776
1280
256
3392
16256
256
46432
inuse
16
0
111
80
8
7
66
2
11
18
20
0
25
137
1
14
freed
0
0
0
0
0
2
0
0
0
7
mapb
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Chapter 5. Network performance tools
181
temp
8
13
0
7424
15744
0
Streams mblk statistic failures:
0 high priority mblk failures
0 medium priority mblk failures
0 low priority mblk failures
The first paragraph of data shows how much memory is allocated to mbufs. The
total number of bytes allocated for mbufs is the first statistic you should review. In
this example, 4 KB is allocated out of a possible limit 16 MB. This limit can be
regulated by the thewall kernel variable. The second statistic is named requests
for mbufs denied. The nonzero value indicates that you should increase the limit
by setting the thewall value. To check the thewall value, enter:
# no -o thewall
thewall = 16384
For network protocol statistics, use the netstat command with the -p flag and the
appropriate protocol name. To receive statistics for IP protocol, use the
command as follows:
# netstat -p IP
ip:
:
59821 total packets received
0 bad header checksums
0 with size smaller than minimum
0 with data size < data length
0 with header length < data size
0 with data length < header length
0 with bad options
0 with incorrect version number
7985 fragments received
0 fragments dropped (dup or out of space)
7 fragments dropped after timeout
3989 packets reassembled ok
55825 packets for this host
....
47289 packets sent from this host
8 packets sent with fabricated ip header
0 output packets dropped due to no bufs, etc.
0 output packets discarded due to no route
11000 output datagrams fragmented
22000 fragments created
0 datagrams that can't be fragmented
....
0 ipintrq overflows
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When the ipintrq overflows counter has a nonzero value, you should change the
length of the IP input queue using the no command:
# no -o ipqmaxlen=100
To display statistics for each protocol, enter:
# netstat -s -f inet|more
ip:
191583 total packets received
0 bad header checksums
0 with size smaller than minimum
0 with data size < data length
0 with header length < data size
0 with data length < header length
0 with bad options
0 with incorrect version number
0 fragments received
0 fragments dropped (dup or out of space)
0 fragments dropped after timeout
0 packets reassembled ok
164680 packets for this host
37 packets for unknown/unsupported protocol
......
......
To check the amount of packets that pass through interfaces and the number of
input/output errors, use the following command:
# netstat -i
Name Mtu Network
lo0
16896 link#1
lo0
16896 127
lo0
16896 ::1
en0
1500 link#2
en0
1500 10.47
tr0
1492 link#3
tr0
1492 9.3.240
Address
localhost.austin.
8.0.5a.fc.d2.e1
server4_
0.4.ac.61.73.f7
server4f
Ipkts Ierrs
282515
282515
282515
49995
49995
730283
730283
0
0
0
0
0
0
0
Opkts Oerrs Coll
283832
0
283832
0
283832
0
27187 3929
27187 3929
317239
722
317239
722
0
0
0
0
0
0
0
5.4.4 The entstat command
The entstat command is a network analysis tool used for Ethernet networks.
You should use this command to display the statistics gathered by the specified
Ethernet device driver. You can also optionally specify that the device-specific
statistics be displayed in addition to the device generic statistics. If no flags are
specified, only the device-generic statistics are displayed. This command is also
invoked when the netstat command is run with the -v flag. The netstat
command does not issue any entstat command flags.
Chapter 5. Network performance tools
183
For example, to display the device generic statistics for ent0, enter:
# entstat ent0
------------------------------------------------------------ETHERNET STATISTICS (ent0) :
Device Type: IBM 10/100 Mbps Ethernet PCI Adapter (23100020)
Hardware Address: 00:06:29:b9:1f:08
Elapsed Time: 1 days 4 hours 54 minutes 56 seconds
Transmit Statistics:
-------------------Packets: 16748
Bytes: 6778818
Interrupts: 48
Transmit Errors: 25
Packets Dropped: 1
Receive Statistics:
------------------Packets: 216281
Bytes: 29241933
Interrupts: 211132
Receive Errors: 0
Packets Dropped: 0
Bad Packets: 0
Max Packets on S/W Transmit Queue: 20
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 1
Broadcast Packets: 1160
Multicast Packets: 2
No Carrier Sense: 25
DMA Underrun: 0
Lost CTS Errors: 0
Max Collision Errors: 0
Late Collision Errors: 0
Deferred: 0
SQE Test: 1
Timeout Errors: 0
Single Collision Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 1
Broadcast Packets: 198718
Multicast Packets: 38
CRC Errors: 0
DMA Overrun: 0
Alignment Errors: 0
No Resource Errors: 0
Receive Collision Erro
Packet Too Short Error
Packet Too Long Errors
Packets Discarded by A
Receiver Start Count:
General Statistics:
------------------No mbuf Errors: 0
Adapter Reset Count: 0
Adapter Data Rate: 200
Driver Flags: Up Broadcast Running
Simplex AlternateAddress 64BitSupport
PrivateSegment DataRateSet
5.4.5 The fddistat command
The fddistat command is a network analysis tool used for FDDI networks. You
should use this command to display the statistics gathered by the specified FDDI
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
device driver. If no flags are specified, only the device driver statistics are
displayed. This command is also invoked when the netstat command is run with
the -v flag. The netstat command does not issue any fddistat command flags.
If you issue an invalid Device_Name, the fddistat command will produce an
error message stating that it could not connect to the device.
The -r flag resets all the statistics back to their initial values. This flag can only be
issued by privileged users.
For example, to display the device driver statistics for fddi0, enter:
# fddistat fddi0
FDDI STATISTICS (fddi0) :
Elapsed Time: 0 days 0 hours 1 minutes 3 seconds
Transmit Statistics:
Receive Statistics:
Packets: 100
Packets: 100
Bytes: 113800
Bytes: 104700
Interrupts: 100
Interrupts: 100
Transmit Errors: 0
Receive Errors: 0
Packets Dropped: 0
Packets Dropped: 0
Max Packets on S/W Transmit Queue: 0
Bad Packets: 0
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0
Broadcast Packets: 0
Broadcast Packets: 0
Multicast Packets: 0
Multicast Packets: 0
General Statistics:
No mbuf Errors: 0
SMT Error Word: 00040080
Connection Policy Violation: 0000
Set Count Hi: 0000 Set Count Lo: 0003
Adapter Check Code: 0000
ECM State Machine:
PCM State Machine Port
PCM State Machine Port
CFM State Machine Port
CFM State Machine Port
CF State Machine:
MAC CFM State Machine:
RMT State Machine:
A:
B:
A:
B:
SMT Event Word: 000004a0
Port Event: 0000
Purged Frames: 0
IN
CONNECT
ACTIVE
ISOLATED
CONCATENATED
C_WRAP_B
PRIMARY
RING_OP
Driver Flags: Up Broadcast Running
Simplex DualAttachStation
Chapter 5. Network performance tools
185
5.4.6 The tokstat
The tokstat command is a network analysis tool used for token ring networks.
You should issue this command to display the statistics gathered by the specified
token-ring device driver. You can optionally specify that the device-specific
statistics be displayed in addition to the device-driver statistics. If no flags are
specified, only the device-driver statistics are displayed. This command is also
invoked when the netstat command is run with the -v flag. The netstat
command does not issue any tokstat command flags.
For example, to display the device-driver statistics for tok0, enter:
# tokstat tok0
TOKEN-RING STATISTICS (tok0) :
Device Type: Token-Ring High-Performance Adapter (8fc8)
Hardware Address: 10:00:5a:4f:26:c1
Elapsed Time: 0 days 0 hours 8 minutes 33 seconds
Transmit Statistics:
Receive Statistics:
-------------------------------------Packets: 191
Packets: 8342
Bytes: 17081
Bytes: 763227
Interrupts: 156
Interrupts: 8159
Transmit Errors: 0
Receive Errors: 0
Packets Dropped: 0
Packets Dropped: 0
Max Packets on S/W Transmit Queue: 17 Bad Packets: 0
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0
Broadcast Packets: 1
Multicast Packets: 0
Timeout Errors: 0
Current SW Transmit Queue Length: 0
Current HW Transmit Queue Length: 0
Broadcast Packets: 8023
Multicast Packets: 0
Receive Congestion Errors: 0
General Statistics:
------------------No mbuf Errors: 0
Lobe Wire Faults: 0
Abort Errors: 0
AC Errors: 0
Burst Errors: 0
Frame Copy Errors: 0
Frequency Errors: 0
Hard Errors: 0
Internal Errors: 0
Line Errors: 0
Lost Frame Errors: 0
Only Station: 0
Token Errors: 0
Remove Received: 0
Ring Recovered: 0
Signal Loss Errors: 0
Soft Errors: 0
Transmit Beacon Errors: 0
Driver Flags: Up Broadcast Running
AlternateAddress ReceiveFunctionalAddr
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5.4.7 The atmstat
The atmstat command shows Asynchronous Transfer Mode (ATM) Adapters
statistics. You can optionally specify that the device-specific statistics be
displayed in addition to the device-generic statistics. If no flags are specified,
only the device-generic statistics are displayed.
To display the adapter-generic statistics for atm0, enter the following example:
# atmstat atm0
ATM STATISTICS (atm0) :
Device Type: Turboways 155 MCA ATM Adapter
Hardware Address: 08:00:5a:99:88:d5
Elapsed Time: 2 days 23 hours 38 minutes 18 seconds
Transmit Statistics:
-------------------Packets: 50573
Bytes: 2225182
Interrupts: 0
Transmit Errors: 0
Packets Dropped: 0
Receive Statistics:
------------------Packets: 0
Bytes: 0
Interrupts: 12904
Receive Errors: 0
Packets Dropped: 0
Bad Packets: 0
Max Packets on S/W Transmit Queue: 0
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0
Cells Transmitted: 50573
Out of Xmit Buffers: 0
Current HW Transmit Queue Length: 0
Current SW Transmit Queue Length: 0
Cells Received: 0
Out of Rcv Buffers: 0
CRC Errors: 0
Packets Too Long: 0
Incomplete Packets: 0
Cells Dropped: 0
General Statistics:
------------------No mbuf Errors: 0
Adapter Loss of Signals: 0
Adapter Reset Count: 0
Driver Flags: Up Running Simplex
64BitSupport
Virtual Connections in use: 2
Max Virtual Connections in use: 2
Virtual Connections Overflow: 0
SVC UNI Version: auto_detect
Turboways ATM Adapter Specific Statistics:
--------------------------------------------------Packets Dropped - No small DMA buffer: 0
Chapter 5. Network performance tools
187
Packets Dropped - No medium DMA buffer: 0
Packets Dropped - No large DMA buffer: 0
Receive Aborted - No Adapter Receive Buffer: 0
Transmit Attempted - No small DMA buffer: 0
Transmit Attempted - No medium DMA buffer: 0
Transmit Attempted - No large DMA buffer: 0
Transmit Attempted - No MTB DMA buffer: 0
Transmit Attempted - No Adapter Transmit Buffer: 0
Max Hardware transmit queue length: 12
Small Mbuf in Use: 0
Medium Mbuf in Use: 0
Large Mbuf in Use: 64
Huge Mbuf in Use: 0
MTB Mbuf in Use: 0
Max Small Mbuf in Use: 0
Max Medium Mbuf in Use: 0
Max Large Mbuf in Use: 64
Max Huge Mbuf in Use: 0
MTB Mbuf in Use: 0
Small Mbuf overflow: 0
Medium Mbuf overflow: 0
Large Mbuf overflow: 0
Huge Mbuf overflow: 0
MTB Mbuf overflow: 0
5.4.8 The netpmon command
The netpmon command is the tool used for network I/O analysis. It uses trace as
a means to collect statistics about events occurring in the network code in the
kernel. Tracing must be stopped using a trcstop command. The netpmon
command monitors a trace of system events, and reports on network activity and
performance during the monitored interval. By default, the netpmon command
runs in the background while one or more application programs or system
commands are being executed and monitored. The netpmon command
automatically starts and monitors a trace of network-related system events in
real time. By default, the trace is started immediately; optionally, tracing may be
deferred until the user issues a trcon command. When tracing is stopped by a
trcstop command, the netpmon command generates all specified reports and
exits. In the client-server environment, netpmon gives an excellent picture of how
networking affects the overall performance. The netpmon command can be run
on both the client and server. The netpmon command focuses on the following
physical and logical resources:
CPU usage
188
Monitors CPU usage by all threads and interrupt
handlers. It estimates how much of this usage is due
to network-related activities.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Network device-driver I/O Monitors I/O operations through network device
drivers. In the case of transmission I/O, the
command also monitors utilizations, queue lengths,
and destination hosts.
Internet socket calls
Monitors all subroutines on IP sockets.
NFS I/O
Monitors read and write subroutines on client
Network File System (NFS) files, client NFS remote
procedure call (RPC) requests, and NFS server read
or write requests.
The following example shows how network operation can impact the CPU
performance. There was an NFS workload during this netpmon session.
# netpmon -O cpu; sleep 10 ; trcstop
on Jul 10 18:08:31 2000
System: AIX server1 Node: 4 Machine: 000BC6FD4C00
========================================================================
Process CPU Usage Statistics:
----------------------------Network
Process (top 20)
PID CPU Time
CPU %
CPU %
---------------------------------------------------------kproc
774
1.4956 24.896
0.000
kproc
516
1.4940 24.870
0.000
kproc
1032
1.4929 24.852
0.000
kproc
1290
1.4854 24.727
0.000
kproc
2064
0.0089
0.148
0.000
topas
14798
0.0051
0.084
0.000
netpmon
19204
0.0035
0.059
0.000
nfsd
25054
0.0026
0.044
0.044
ksh
5872
0.0010
0.016
0.000
dtterm
17910
0.0009
0.014
0.000
netpmon
22732
0.0007
0.012
0.000
trace
28206
0.0006
0.010
0.000
swapper
0
0.0005
0.008
0.000
xterm
21984
0.0004
0.007
0.001
X
4212
0.0003
0.005
0.000
trcstop
11070
0.0002
0.004
0.000
java
17448
0.0002
0.003
0.000
init
1
0.0001
0.002
0.000
dtwm
10160
0.0001
0.002
0.000
ot
27694
0.0001
0.001
0.000
---------------------------------------------------------Total (all processes)
5.9933 99.767
0.045
Idle time
0.0000
0.000
Chapter 5. Network performance tools
189
========================================================================
/the output was edited for brevity/
Note that only the nfsd daemon consumed the network CPU time. The network
CPU time means percentage of total time that the interrupt handler executed on
behalf of network-related events. For other statistics, use the netpmon command
with the -O flag and the appropriate keyword. The possible keywords are cpu, dd
(network device driver I/O), so (Internet socket call I/O), nfs (NFS I/O), and all.
5.4.9 The tcpdump and iptrace commands
The tools discussed previously allow you to obtain a various number of statistics
and network-type events in the AIX kernel. However, you might get a problem
where statistic counters are not enough to find the cause of the problem. You
may need to see the real data crossing the wire. There are two commands that
let you see every incoming and outgoing packet from your interface: tcpdump and
iptrace.
The tcpdump command prints out the headers of packets captured on a specified
network interface. The following example shows a telnet session between hosts
9.3.240.59 and 9.3.240.58:
# tcpdump -i tr0 -n -I -t dst host 9.3.240.58
9.3.240.59.44183 > 9.3.240.58.23: S 1589597023:1589597023(0) win 16384 <mss
1452> [tos 0x10]
9.3.240.58.23 > 9.3.240.59.44183: S 1272672076:1272672076(0) ack 1589597024 win
15972 <mss 1452>
9.3.240.59.44183 > 9.3.240.58.23: . ack 1 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: . ack 1 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: P 1:16(15) ack 1 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: P 1:16(15) ack 1 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: . ack 6 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: . ack 6 win 15972 [tos 0x10]
9.3.240.58.23 > 9.3.240.59.44183: P 6:27(21) ack 1 win 15972 (DF)
9.3.240.59.44183 > 9.3.240.58.23: P 1:27(26) ack 27 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: P 1:27(26) ack 27 win 15972 [tos 0x10]
9.3.240.58.23 > 9.3.240.59.44183: P 27:81(54) ack 27 win 15972 (DF)
9.3.240.59.44183 > 9.3.240.58.23: P 27:30(3) ack 81 win 15972 [tos 0x10]
9.3.240.59.44183 > 9.3.240.58.23: P 27:30(3) ack 81 win 15972 [tos 0x10]
The first line indicates that TCP port 44183 on host 9.3.240.59 sent a packet to
the telnet port (23) on host 9.3.240.58. The S indicates that the SYN flag was set.
The packet sequence number was 1589597023 and it contained no data. There
was no piggy-backed ack field; the available receive field win was 16384 bytes
and there was a max-segment-size (mss) option requesting a mss of 1452 bytes.
Host 9.3.240.58 replies with a similar packet, except it includes a piggy-backed
ack field for host 9.3.240.59 SYN. Host 9.3.240.59 then acknowledges the host
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
9.3.240.58 SYN. The period (.) means no flags were set. The packet contains no
data, so there is no data sequence number. On the eleventh line, host 9.3.240.59
sends host 9.3.240.58 26 bytes of data. The PUSH flag is set in the packet. On
the twelfth line, host 9.3.240.58 says it received data sent by host 9.3.240.59 and
sends 54 bytes of data; it also includes a piggy-backed ack for sequence number
27.
The iptrace daemon records IP packets received from configured interfaces.
Command flags provide a filter so that the daemon traces only packets meeting
specific criteria. Packets are traced only between the local host on which the
iptrace daemon is invoked and the remote host. To format iptrace output, run
the ipreport command. The following example shows the query from host
9.3.240.59 to DNS server 9.3.240.2. The output from the nslookup command is
shown in the following:
# nslookup www.prokom.pl
Server: dhcp240.itsc.austin.ibm.com
Address: 9.3.240.2
Non-authoritative answer:
Name:
mirror.prokom.pl
Address: 153.19.177.201
Aliases: www.prokom.pl
The data was captured by the iptrace command, similar to the following:
# iptrace -a -P UDP -s 9.3.240.59 -b -d 9.3.240.2 /tmp/dns.query
The output form the iptrace command was formatted by the ipreport
command, as follows:
TOK: ====( 81 bytes transmitted on interface tr0 )==== 17:14:26.406601066
TOK: 802.5 packet
TOK: 802.5 MAC header:
TOK: access control field = 0, frame control field = 40
TOK: [ src = 00:04:ac:61:73:f7, dst = 00:20:35:29:0b:6d]
TOK: 802.2 LLC header:
TOK: dsap aa, ssap aa, ctrl 3, proto 0:0:0, type 800 (IP)
IP: < SRC =
9.3.240.59 > (server4f.itsc.austin.ibm.com)
IP: < DST =
9.3.240.2 > (dhcp240.itsc.austin.ibm.com)
IP: ip_v=4, ip_hl=20, ip_tos=0, ip_len=59, ip_id=64417, ip_off=0
IP: ip_ttl=30, ip_sum=aecc, ip_p = 17 (UDP)
UDP: <source port=49572, <destination port=53(domain) >
UDP: [ udp length = 39 | udp checksum = 688d ]
DNS Packet breakdown:
QUESTIONS:
www.prokom.pl, type = A, class = IN
TOK: ====( 246 bytes received on interface tr0 )==== 17:14:26.407798799
Chapter 5. Network performance tools
191
TOK: 802.5 packet
TOK: 802.5 MAC header:
TOK: access control field = 18, frame control field = 40
TOK: [ src = 80:20:35:29:0b:6d, dst = 00:04:ac:61:73:f7]
TOK: routing control field = 02c0, 0 routing segments
TOK: 802.2 LLC header:
TOK: dsap aa, ssap aa, ctrl 3, proto 0:0:0, type 800 (IP)
IP: < SRC =
9.3.240.2 > (dhcp240.itsc.austin.ibm.com)
IP: < DST =
9.3.240.59 > (server4f.itsc.austin.ibm.com)
IP: ip_v=4, ip_hl=20, ip_tos=0, ip_len=222, ip_id=2824, ip_off=0
IP: ip_ttl=64, ip_sum=7cc3, ip_p = 17 (UDP)
UDP: <source port=53(domain), <destination port=49572 >
UDP: [ udp length = 202 | udp checksum = a7bf ]
DNS Packet breakdown:
QUESTIONS:
www.prokom.pl, type = A, class = IN
ANSWERS:
-> www.prokom.plcanonical name = mirror.prokom.pl
-> mirror.prokom.plinternet address = 153.19.177.201
AUTHORITY RECORDS:
-> prokom.plnameserver = phobos.prokom.pl
-> prokom.plnameserver = alfa.nask.gda.pl
-> prokom.plnameserver = amber.prokom.pl
ADDITIONAL RECORDS:
-> phobos.prokom.plinternet address = 195.164.165.56
-> alfa.nask.gda.plinternet address = 193.59.200.187
-> amber.prokom.plinternet address = 153.19.177.200
There are two packets shown on the ipreport output above (the key data is
shown in bold face text). Every packet is divided into a few parts. Each part
describes a different network protocol levels. There are the token ring (TOK), IP,
UDP, and the application (DNS) parts. The first packet is sent by host 9.3.240.59
and is a query about the IP address of the www.prokom.pl host. The second one
is the answer.
5.5 Network performance management tools
Use the no command to configure network attributes. The no command sets or
displays current network attributes in the kernel. This command only operates on
the currently running kernel. The command must be run again after each startup
or after the network has been configured. To make changes permanent, make
changes to the appropriate /etc/rc. file. To list the current value of every
parameter you can change, use the following command:
# no -a
extendednetstats = 1
thewall = 18420
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
sockthresh = 85
sb_max = 1048576
somaxconn = 1024
.....
lowthresh = 90
medthresh = 95
psecache = 1
subnetsarelocal = 1
maxttl = 255
ipfragttl = 60
ipsendredirects = 1
ipforwarding = 1
udp_ttl = 30
tcp_ttl = 60
arpt_killc = 20
tcp_sendspace = 16384
tcp_recvspace = 16384
udp_sendspace = 9216
udp_recvspace = 41920
.....
To change the value of the thewall system parameter, shown as 18420, to
36840, use the no command, as shown in the following.
# no -o thewall=36840
The ifconfig command can be used to assign an address to a network interface
or to configure or display the current configuration information. For tuning
purposes, it is used to change the MTU size:
# ifconfig en0 mtu 1024
Note: The MTU parameters have to be the same on all nodes of the network.
The chdev command is also used to change the value of system attributes. The
changes made by the chdev command are permanent because they are stored in
the ODM database. To display the current value of the parameters of the en0
interface, use the lsattr command, as follows.
# lsattr -El en0
mtu
1500
remmtu
576
netaddr
10.47.1.6
state
up
arp
on
netmask
255.255.0.0
security
none
authority
broadcast
Maximum IP Packet Size for This Device
Maximum IP Packet Size for REMOTE Networks
Internet Address
Current Interface Status
Address Resolution Protocol (ARP)
Subnet Mask
Security Level
Authorized Users
Broadcast Address
True
True
True
True
True
True
True
True
True
Chapter 5. Network performance tools
193
netaddr6
alias6
prefixlen
alias4
rfc1323
tcp_nodelay
tcp_sendspace
tcp_recvspace
tcp_mssdflt
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
True
True
True
True
True
True
True
True
True
To permanently change value of the MTU parameter, enter:
# chdev -l en0 -a mtu=1024
en0 changed
5.6 Name resolution
If a network connection seems inexplicably slow at times but reasonable at other
times, you should check the name resolution configuration for your system. To
perform a basic diagnostic for name resolving, you can use either the host
command or the nslookup command.
# host dhcp240.itsc.austin.ibm.com
dhcp240.itsc.austin.ibm.com is 9.3.240.2
The name resolution can be served through either the remote DNS server or the
remote NIS server. If one of them is down, you have to wait until a TCP time-out
occurs. The name can be resolved by an alternate source, which can be a
secondary name server or the local /etc/hosts file.
First check the /etc/netsvc.conf file or NSORDER environment variable for your
particular name resolution ordering. Then check the /etc/resolv.conf file for the IP
address of the name server and try to ping it. If you can ping it, then it is up and
reachable. If not, try a different name resolution ordering.
Resolver routines on hosts running TCP/IP attempt to resolve names using
sources listed in Table 5-1.
Table 5-1 Default search order for the nslookup command
194
Default
nsorder
lookup
Description
1. BIND / DNS
Resolver routines will look for /etc/resolv.conf by default.
2. NIS
NIS is queried if it is running. NIS is authoritative over the local
/etc/hosts.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Default
nsorder
lookup
Description
3. /etc/hosts
If NIS is not running then the local /etc/host file is searched.
5.7 NFS performance tuning
This section discusses the NFS server and the NFS client performance issue.
5.7.1 NFS server-side performance
When narrowing down the performance discussion on servers to the NFS
specifics, the issue is often related to dropped packages. NFS servers may drop
packets due to overloads.
One common place where a server will drop packets is the UDP socket buffer.
The default for AIX Version 4.3 is TCP for data transfer, but UDP is still used for
mounting. Dropped packets here are counted by the UDP layer, and the statistics
can be seen by using the netstat -p UDP command. For example:
# netstat -p UDP
udp:
89827 datagrams received
0 incomplete headers
0 bad data length fields
0 bad checksums
329 dropped due to no socket
77515 broadcast/multicast datagrams dropped due to no socket
0 socket buffer overflows
11983 delivered
11663 datagrams output
(At the test system the buffer size was sufficient)
NFS packets will usually be dropped at the socket buffer only when a server has
a lot of NFS write traffic. The NFS server uses a UDP and TCP socket attached
to the NFS port, and all incoming data is buffered on those ports. The default size
of this buffer is 60000 bytes. Dividing that number by the size of the default NFS
Version 3 write packet (32765), you find that it will take only two simultaneous
write packets to overflow that buffer. That could be done by just one NFS client
(with the default configurations). It is not as easy as it sounds to overflow the
buffer in normal system operation. As soon as the first packet reaches the
socket, an nfsd will be awakened to start taking the data off.
Chapter 5. Network performance tools
195
One of two things has to happen for packets to be dropped. There must be high
volume or a high burst of traffic on the socket. If there is high volume, a mixture of
many writes plus other possibly non-write NFS traffic, there may not be enough
nfsd daemons to take the data off the socket fast enough to keep up with the
volume (it takes a dedicated nfsd to service each NFS call of any type). In the
high burst case, there may be enough nfsds, but the speed at which packets
arrive on the socket is such that the nfsd daemons cannot wake up fast enough
to keep it from overflowing.
Each of the two situations has a different resolution. In the case of high volume, it
may be sufficient to just increase the number of nfsd daemons running on the
system. Since there is no significant penalty for running with more nfsd daemons
on an AIX machine, this should be tried first. This can be done with the following
command:
# chnfs -n 16
This will stop the currently running daemons, modify the SRC database code to
reflect the new number, and restart the daemons indicated.
In the case of a high burst of traffic, the only solution is to make the socket bigger
in the hope that some reasonable size will be sufficiently large enough to give the
nfsd daemons time to catch up with the burst. Memory dedicated to this socket
will not be available for any other use so it must be understood that making the
socket larger may result in memory that will be under utilized the vast majority of
the time. The cautious administrator will watch the socket buffer overflows
statistic and correlate it with performance problems and make a determination on
how big to make the socket buffer.
The nfso command is a great utility to list and configure NFS network variables.
The syntax for this command is:
nfso { -a | -d Option | -l HostName | -o Option [ =NewValue ] } [ -c ]
Note: The nfso command performs no range checking; therefore, it accepts
all values for the variables. If used incorrectly, the nfso command can make
your system inoperable.
For example, to check the NFS kernel options of nfs_socketsize,
nfs_tcp_socketsize, use the nfso command:
# nfso -a
portcheck= 0
udpchecksum= 2
nfs_socketsize= 60000
nfs_tcp_socketsize= 60000
nfs_setattr_error= 0
nfs_gather_threshold= 4096
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
nfs_repeat_messages= 0
nfs_udp_duplicate_cache_size= 0
nfs_tcp_duplicate_cache_size= 5000
nfs_server_base_priority= 0
nfs_dynamic_retrans= 1
nfs_iopace_pages= 0
nfs_max_connections= 0
nfs_max_threads= 8
nfs_use_reserved_ports= 0
nfs_device_specific_bufs= 1
nfs_server_clread= 1
nfs_rfc1323= 0
nfs_max_write_size= 0
nfs_max_read_size= 0
nfs_allow_all_signals= 0
These configurable variables can be also be set with the nfso command. For
example, to set the udpchecksum variable to its default value of 1, enter:
# nfso -d udpchecksum
If you change the nfsbuffer sizes, you must verify that the kernel variable sb_max
is greater than the NFS buffer values chosen. The default value of sb_max is
1048576 on AIX 5L Version 5.1. If you need to increase the sb_max value, use
the no command. Remember that everything changed with no or nfso is valid
only until the next boot, unless these changes have been added to a boot script,
for example, /etc/rc.nfs.
5.7.2 NFS client-side performance
The NFS client performance topic often concentrates on the number of biod
daemons used. For biod daemons, there is a default number of biod daemons
(six for a NFS Version 2 mount, four for a NFS Version 3 mount) that may
operate on any one remote-mounted file system concurrently. The idea behind
this limitation is that allowing more than a set number of biod daemons to operate
against the server at one time may overload the server. Since this is
Config_Rules on a per-mount basis on the client, adjustments can be made to
configure client mounts by the server capabilities.
When evaluating how many biod daemons to run, you should consider the server
capabilities as well as the typical NFS usage on the client machine. If there are
multiple users or multiple processes on the client that will need to perform NFS
operations to the same NFS-mounted file systems, you have to be aware that
contention for biod services can occur with just two simultaneous read or write
operations.
Chapter 5. Network performance tools
197
Up to six biod daemons can be working on reading a file in one NFS file system.
If another read starts in another NFS-mounted file system, both reads will be
attempting to use all six biod daemons. In this case, presuming that the server(s)
are not already overloaded, performance will likely improve by increasing the
biod number to 12. This can be done using the chnfs command:
# chnfs -b 12
On the other hand, suppose both file systems are mounted from the same server
and the server is already operating at peak capacity. Adding another six biod
daemons could dramatically worsen the response due to the server dropping
packets and resulting in time-outs and retransmits.
5.7.3 Mount options
The mount command has several NFS-specific options that may affect
performance.
The most useful options are used to set the read and write sizes to some value
that changes the read/write packet size that is sent to the server.
For NFS Version 3 mounts, the read/write sizes can be both increased and
decreased. The default read/write sizes are 32 KB. The maximum possible on
AIX at the time of publication is 61440 bytes (60 x 1024). Using 60 KB, read/write
sizes may provide slight performance improvement in specialized environments.
To increase the read/write sizes when both server and client are AIX machines
requires modifying settings on both machines. On the client, the mount must be
performed by setting up the read/write sizes with the -o option. For example, -o
rsize=61440,wsize=61440. On the server, the advertised maximum read/write
size is configured through use of the nfso command using the
nfs_max_write_size and nfs_max_read_size parameters. For example:
# nfso -o nfs_max_write_size=61440
NFS Version 3 uses TCP by default, while NFS Version 2 uses UDP only. This
means the initial client mount request using TCP will fail. To provide backwards
compatibility, the mount is retried using UDP, but this only occurs after a time-out
of some minutes. To avoid this problem, NFS Version 3 provided the proto and
vers parameters with the mount command. These parameters are used with the
-o option to hardwire the protocol and version for a specific mount. The following
example forces the use of UDP and NFS Version 2 for the mount request:
# mount -o proto=udp,vers=2,soft,retry=1 server4:/tmp /mnt
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5.8 Command summary
The following section provides a list of the key commands discussed in this
chapter.
5.8.1 The netstat command
The syntax of the netstat command is as follows.
To display active sockets for each protocol or routing table information:
/bin/netstat [ -n ] [ { -A -a } | { -r -i -I interface } ]
[ -f AddressFamily ] [ -p protocol ] [ interval ] [ system ]
To display the contents of a network data structure:
/bin/netstat [ -m | -s | -ss | -u | -v ] [
[ -p protocol ] [ interval ] [ system ]
-f AddressFamily ]
To display the packet counts throughout the communications subsystem:
/bin/netstat -D
To display the network buffer cache statistics:
/bin/netstat -c
To display the data link provider interface statistics:
/bin/netstat -P
To clear the associated statistics:
/bin/netstat [ -Zc | -Zi | -Zm | -Zs ]
Some useful netstat flags from a NFS perspective are provided in Table 5-2.
Table 5-2 Commonly used flags of the netstat command
Flags
Description
-P protocol
Shows statistics about the value specified for the protocol variable
-s
Shows statistics for each protocol
-D
Shows the number of packets received, transmitted, and dropped in
the communications subsystem
Chapter 5. Network performance tools
199
5.8.2 The tcpdump command
The syntax of the tcpdump command is:
tcpdump [ -I ] [ -n ] [ -N ] [ -t ] [ -v ] [ -c count ] [ -i interface ]
[ -w file ] [ Expression ]
Some useful tcpdump flags are provided in Table 5-3.
Table 5-3 Commonly used flags of the tcpdump command
Flags
Description
-c count
Exits after receiving count packets.
-n
Omits conversion of addresses to names.
-N
Omits printing domain name qualification of host names.
-t
Omits the printing of a timestamp on each dump line.
-i interface
Listens on interface.
5.8.3 The iptrace command
The syntax of the iptrace command is:
iptrace [ -a ] [ -e ] [ -Pprotocol ] [ -iinterface ] [ -pport ]
[ -shost [ -b ] ] [ -dhost [ -b ] ] LogFile
Some useful iptrace flags are provided in Table 5-4.
Table 5-4 Commonly used flags of the iptrace command
Flags
Description
-a
Suppresses ARP packets.
-s host
Records packets coming from the source host specified by the host
variable.
-b
Changes the -d or -s flags to bidirectional mode.
5.8.4 The ipreport command
The syntax of the ipreport command is:
ipreport [ -e ] [ -r ] [ -n ] [ -s ] LogFile
Some useful ipreport flags are provided in Table 5-5 on page 201.
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Table 5-5 Commonly used flags of the ipreport command
Flags
Description
-s
Prepends the protocol specification to every line in a packet
-r
Decodes remote procedure call (RPC) packets
-n
Includes a packet number to facilitate easy comparison of different
output formats
5.9 Quiz
The following assessment questions help verify your understanding of the topics
discussed in this chapter.
1. Which of the following commands is most useful in collecting data to
determine a network performance problem?
A.
iostat
B.
lpstat
C. netstat
D.
vmstat
2. Which of the following commands should be used to test name resolution
response?
A.
host
B.
iostat
C. ifconfig
D.
hostname
3. Which of the following commands should be used to identify the cause of
packet sequence problems?
A.
tprof and gprof
B.
netstat and iostat
C. lsattr and ifconfig
D.
iptrace and tcpdump
4. Which of the following commands should be used to make a difference when
tuning NFS on a client system?
A.
mount
B.
vmtune
C. exportfs
Chapter 5. Network performance tools
201
D.
schedtune
5. On an NFS server, netstat -m is run once and then again 15 minutes later.
# date
Mon Jun 12 20:05:54 CDT 1995
# netstat -m
1385 mbufs in use:
96 mbuf cluster pages in use
2170 Kbytes allocated to mbufs
841 requests for mbufs denied
0 calls to protocol drain routines
Kernel malloc statistics:
By sizeinusecallsfailedfreehiwat freed
32 301 27870 211 640 0
64 41 318 0 23 320 0
128 117 18140 43 160 0
256 138 63911620223840
512 20 11120 20 40 0
10242 77 0 2 20 0
20480 33 0 2 10 0
409696 335617841111200
163841 1 0 12 24 7
# date
Mon Jun 12 20:20:04 CDT 1995
# netstat -m
1389 mbufs in use:
97 mbuf cluster pages in use
2180 Kbytes allocated to mbufs
982 requests for mbufs denied
0 calls to protocol drain routines
Kernel malloc statistics:
By sizeinusecallsfailedfreehiwatfreed
32 301 27870 211 640 0
64 41 318 0 23 320 0
128 117 18140 43 160 0
256 138 63911620223840
512 20 11120 20 40 0
10242 77 0 2 20 0
20480 33 0 2 10 0
409697 338610982111200
163841 1 0 12 24 7
An extract of the output for both times is shown in the preceding exhibits.
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Using the netstat outputs, which of the following conclusions is most
appropriate to draw?
A.
The number of biod(s) should be increased.
B.
The number of nfsd(s) should be increased.
C. The machine needs more physical memory.
D.
The machine needs more memory allocated for mbufs.
6. There is a TCP/IP application that receives files from a remote machine. The
application reads 32 kilobytes of data at a time to the socket, but has not
issued a system call to set the window size. Which of the following
procedures should be performed on the local machine to increase the
throughput of the application?
A.
Increase the size of thewall.
B.
Increase the size of sb_max.
C. Increase the size of tcp_recvspace.
D.
Increase the size of tcp_sendspace.
7. Which of the following tools should be used to determine network latency or
delay?
A.
arp
B.
netstat
C. ifconfig
D.
traceroute
8. When analyzing network I/O performance, which of the following commands
should be run?
A.
vmstat
B.
iostat
C. netstat -s
D.
wlmstat
9. Which nfso option will print a list of all configurable options and their current
values?
A.
nfso -l
B.
nfso -o
C. nfso -d
D.
nfso -a
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203
5.9.1 Answers
The following are the preferred answers to the questions provided in this section.
1. C
2. A
3. D
4. A
5. D
6. C
7. D
8. C
9. D
5.10 Exercises
The following exercises provide sample topics for self study. They will help
ensure comprehension of this chapter.
1. Capture data from a telnet session using the tcpdump command.
2. Capture data from a telnet session using the iptrace command.
3. Compare outputs from previously captured sessions.
4. Using the no command, check current values of kernel variables.
5. Check protocol statistics with the netstat command using the -p flag.
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6
Chapter 6.
Performance management
tools
In this chapter, the following topics are covered:
 The AIX scheduler
 The multiple run queue design of AIX Version 4.3.3
 The schedtune command
 The nice and renice commands
 Workload Manager introduction
The scope of this chapter concentrates on the thread scheduling and the
possibilities to manipulate the process priorities with the schedtune, nice, and
renice commands. The ps, bindprocessor, emstat, and tprof commands are
also reviewed.
© Copyright IBM Corp. 2002. All rights reserved.
205
6.1 The AIX scheduler
The need for a scheduler for operating system efficiency is paramount. There are
more threads and processes running than there are CPUs on any system. This is
why the operating system is using the scheduler to decide which thread is
allowed to use the CPU at any moment. The scheduler selects the thread to run
from a list of waiting ready-to-run threads on the run queue. The number of
waiting threads on the run queue is provided in the highlighted leftmost column in
the following vmstat output:
# vmstat 2 5
kthr
memory
page
faults
----- ----------- ------------------------ -----------r b
avm
fre re pi po fr
sr cy in
sy cs
0 0 16272 75548
0
0
0
0
0
0 102
21 10
2 1 16272 75547
0
0
0
0
0
0 407 1541 24
2 1 16272 75547
0
0
0
0
0
0 405
58 28
2 1 16272 75547
0
0
0
0
0
0 406
43 25
2 1 16272 75547
0
0
0
0
0
0 409
29 26
cpu
----------us sy id wa
1 0 99 0
49 0 51 0
50 0 50 0
50 0 50 0
50 0 50 0
The threads in the run queue are sorted in priority order, and the thread that has
the highest priority gets to use the CPU. For more information on the relationship
between process and threads, see Chapter 2, “Performance tuning: Getting
started” on page 7.
In AIX Version 4, the five possible values for the thread scheduling policy are as
follows:
206
SCHED_FIFO
This is a non-preemptive scheduling scheme. After a
thread with this policy is scheduled, it runs to completion
unless it is blocked, it voluntarily yields control of the
CPU, or a higher-priority thread becomes dispatchable.
Only fixed-priority threads can have a SCHED_FIFO
scheduling policy.
SCHED_RR
The thread has a fixed priority. When a SCHED_RR
thread has control at the end of the time slice, it moves to
the tail of the queue of dispatchable threads of its priority.
Only fixed-priority threads can have a SCHED_RR
scheduling policy.
SCHED_OTHER
This policy is defined by POSIX Standard 1003.4a as
implementation-defined. In AIX Version 4, this policy is
defined to be equivalent to SCHED_RR, except that it
applies to threads with nonfixed priority. The recalculation
of the running thread's priority at each clock interrupt
means that a thread may lose control because its priority
has risen above that of another dispatchable thread.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
SCHED_FIFO2
This policy is the same as for SCHED_OTHER, except
that it allows a thread that has slept for only a short
amount of time to be put at the head of its run queue
when it is awakened. This policy is only available on AIX
Version 4.3.3 or later.
SCHED_FIFO3
A thread whose scheduling policy is set to
SCHED_FIFO3 is always put at the head of a run queue.
To prevent a thread belonging to the SCHED_FIFO2
scheduling policy from being put ahead of
SCHED_FIFO3, the run queue parameters are changed
when a SCHED_FIFO3 thread is enqueued, so that no
thread belonging to SCHED_FIFO2 will join the head of
the run queue. This policy is only available on AIX Version
4.3.3 or later.
6.1.1 Priority calculation on AIX versions prior to 4.3.2
The priority values differ from AIX versions previous to 4.3.2 and AIX Version
4.3.2 and later. Generally speaking, the lower the value is, the higher is the
priority, with 0 as the lowest value and the greatest priority. The other end is the
value of 127, which is the worst priority a thread can get. This priority value is
reserved for the wait process. While the thread is running (using the CPU), the
priority is recalculated, the value goes up, and the priority goes down. The longer
a thread has existed without using CPU, the lower the value gets and,
accordingly, the higher the priority. At one point, a thread in the run queue will
have a lower value (higher priority) than the current running thread, the thread
running is released, and the thread from the run queue is given CPU time.
As shown in Figure 6-1 on page 208, the global run queue used by AIX versions
prior to 4.3.2 is symbolized. Threads A and B are forced to release control of the
CPUs as soon as higher priority threads become runnable. In this case, threads
C, D, and E are all available. Thread C is chosen first because it has the highest
priority. Threads D and E have equal priority and occupy adjacent positions in
the queue. Thread D is selected because of its position.
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207
Figure 6-1 Run queue prior to AIX Version 4.3.3
Figure 6-1 is a simplification of the actual layout as shown in Figure 6-2 on
page 209. All the dispatchable threads of a given priority occupy consecutive
positions in the run queue. AIX Version 4 maintains 128 run queues. These run
queues relate directly to the range of possible values (0 through 127) for the
priority field for each thread. This method makes it easier for the scheduler to
determine which thread is most favored to run. Without having to search a single
large run queue, the scheduler consults a 128-bit mask where a bit is on to
indicate the presence of a ready-to-run thread in the corresponding run queue.
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Figure 6-2 AIX Version 4, 128 run queues
A thread can be fixed priority or non-fixed priority. The priority value of a
fixed-priority thread is constant, while the priority value of a non-fixed priority
thread is the sum of the maximum priority level for user threads (a constant 40),
the thread’s nice value (the default is 20 for foreground processes and 24 for
background processes), and its CPU penalty.
One of the factors in priority calculation is the recent CPU usage value. One out
of two calculations used in defining the recent CPU usage is:
Recent CPU usage = Old recent CPU usage + 1
This calculation is done 100 times a second (at every tick). The recent CPU
usage value increases by 1 each time the thread is in control of the CPU at the
end of a tick. The maximum value is 120. In other words, running threads have
their recent CPU usage value recalculated (increased) 100 times a second until
reaching the maximum limit of 120. This value is shown in the C column of the ps
command output:
# ps -f
UID
root
root
root
root
PID
12948
13888
15432
15752
PPID
C
STIME
TTY
12796
0 14:27:07 pts/1
12948 111 10:08:34 pts/1
12948
4 11:42:56 pts/1
12948 110 10:08:34 pts/1
TIME
0:00
94:21
0:00
94:21
CMD
ksh
./tctestprg
ps -f
./tctestprg
Chapter 6. Performance management tools
209
Once every second, all threads, including those that are asleep, have their recent
CPU usage value recalculated as follows:
Recent CPU usage = Old recent CPU usage x (SCHED_D / 32)
The default value for SCHED_D is 16, which means that the old recent CPU
usage value is divided by 2 (16 / 32 = 0.5). This prevents the recent CPU usage
values of all processes from being set at a stable 120.
With this value, recent CPU usage, the CPU penalty value can be calculated:
CPU penalty = Recent CPU usage x (SCHED_R / 32)
The default value for SCHED_R is 16. With the CPU penalty value defined, the
priority, also calculated at every tick, can finally be calculated as follows:
Priority value = 40 + nice value + CPU penalty
In this calculation, the default nice value is 20 for foreground processes and 24
for background processes.
With these definitions, you can see that three values can be manipulated for
tuning performance: the nice value, SCHED_R (also called the weighting factor),
and the SCHED_D (also called the decay factor).
6.1.2 Priority calculation on AIX Version 4.3.2 and later
AIX Version 4.3.2 and later added a couple of new definitions to be considered.
First is the NICE factor, which is not the nice value manipulated with the nice
command, but the sum of the maximum priority level for user threads and the
value manipulated by the nice command.
Secondly, the DEFAULT_NICE factor is added to the algorithm. This factor is
equal to the maximum priority level for a user, also named the base value (40),
plus the default nice value for a foreground process (20). In other words, the sum
is 60 for a foreground process (DEFAULT_NICE - NICE = 60).
The following calculation is used for calculating the priority:
Priority = (Recent CPU usage x SCHED_R x (xnice + 4)) / (32 x (DEFAULT_NICE +
4)) + xnice
Where DEFAULT_NICE = 40 + 20 (base value plus default nice). The calculation
for the xnice value is as follows:
xnice = (NICE > DEFAULT_NICE) ? (2 * nice) - 60 : NICE
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This means that if nice is smaller or equal to DEFAULT_NICE, then:
xnice = NICE
But if NICE is greater than DEFAULT_NICE (in other words, if you have
manipulated the thread with the nice command to lessen its priority), then:
xnice = (2 x NICE) - 60
The nice value has a much greater impact on the priority of a thread. It is now
included in the calculation as a multiple of the recent CPU usage, in addition to
its use as a constant factor. To get greater granularity in the run queue(s), the
DEFAULT_NICE is set to 60. Some artificial values will help show the
calculation.
Recent CPU usage = 64
SCHED_R = 16
NICE = 64
Starting with the XNICE calculation:
xnice = (NICE > DEFAULT_NICE) ? (2 * NICE) - 60 : nice
Because NICE is greater then DEFAULT_NICE, then:
xnice = (2 x 64) - 60 = 68
By entering the values given and the XNICE value in the calculation:
Priority = (Recent CPU usage x SCHED_R x (xnice + 4)) / (32 x (DEFAULT_NICE +
4)) + xnice
The calculation will look as follows:
P = (64 x 16 x (68 + 4)) / (32 x 64) + xnice
P = (73728 / 2048) + 64
P = 100
You still have three values to manipulate: The nice value (as in the example),
SCHED_R, and SCHED_D (for recent CPU usage). In the following sections, the
multiple run queue layout and the commands that are used to change these
values are discussed.
6.2 Multiple run queues with load balancing
The run queue is the same global queue on AIX Version 4.3.2 as on AIX Version
4.3.1, but on AIX Version 4.3.3 and later, the run queue layout has changed. AIX
now offers improved cache affinity through the use of multiple run queues. The
new kernel scheduler implements a single global run queue along with a set of
local run queues, where each processor has a dedicated local run queue.
Chapter 6. Performance management tools
211
Once a thread is placed on a local run queue, it generally stays there until an
imbalance is detected. Thresholds are used to limit the amount of load balancing
that takes place.
A diagram of the relationship of the local and global run queues is provided in
Figure 6-3.
Figure 6-3 Run queue on AIX Version 4.3.3 and later
The per-node local run queue competes with the local run queues of the node for
CPUs to service its threads. The priority of the highest thread on a run queue
(both local and global run queues) is maintained in the run queue. The
dispatcher uses this data without holding the run queue locks to make a low
overhead decision of which run queue to search. This mechanism allows the
priorities of the two run queues to be honored most of the time. When both run
queues have threads waiting at the same priority, the local run queue is chosen.
Usually, when initiated, threads get on the global run queue by means of the load
balancing mechanism implemented. Once a CPU dispatches a thread from the
global run queue, it does not generally return to the global run queue, but rather
to the queue served by the CPU dispatching it.
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The load balancing is handled by a number of algorithms designed to keep the
various run queues of a system approximately equally utilized. There are four
balancing algorithms, which are discussed in the following sections.
6.2.1 Initial load balancing
Initial load balancing applies to newly created threads. When an unbound new
thread is created as part of a new process (as well as a new thread for an
existing process), it is placed on an idle CPU (if one exists). If an idle CPU cannot
be found, the thread will be placed in the global queue.
6.2.2 Idle load balancing
Idle load balancing applies when a process would otherwise go idle, running the
waitproc thread (for example, PID 516). When the dispatcher reaches this point
in its logic, it does not just scan other run queues in an attempt to find work at any
cost. It is actually beneficial to allow what appears to be unnecessary idle cycles
rather than moving a thread and losing cache affinity. The steps taken by the idle
load balancing method are:
 Before dispatching the waitproc, search other queues for available work. This
is a stronger statement than work being on another queue. The search
routine will look for a queue that:
– Contains the largest number of runnable threads.
– Contains more runnable threads than the current steal threshold.
– Contains at least one stealable (unbound) thread.
– Has not had steal_max threads already stolen from it over the current
clock tick interval.
The search is done without holding those run queues’ locks.
 To actually steal a thread, the chosen run queue’s lock must be obtained.
This is done by a special call written to avoid interfering with another instance
of the dispatcher. If no lock can be obtained, run the waitproc.
 After getting the lock, check that a stealable thread is still available. If there is
no stealable thread, the waitproc is run.
 Change the threads’ run queue assignment and pointer.
6.2.3 Frequent periodic load balancing
This is performed every N clock ticks (at time of publication, 10). It attempts to
balance the loads on the local queues of a node in much the same way that idle
load balancing does. The idea is to move a thread from the most loaded to the
Chapter 6. Performance management tools
213
least loaded run queue, but if the least loaded run queue has stolen a thread
through idle load balancing in the last interval, nothing is done. The difference in
load factors between the two run queues chosen for frequent periodic load
balancing must be at least 1.5. Idle load balancing is less expensive, so the ideal
situation is if frequent periodic load balancing does not have to interfere.
6.2.4 Infrequent periodic load balancing
If a thread has not received CPU time in the last N.5 (at time of publication 1.5)
seconds, the thread is moved to the global run queue.
6.3 Scheduler performance management
AIX offers several ways to modify the default behavior of the scheduling system
for threads and processes. This section describes the schedtune, nice, and
renice commands.
6.3.1 The schedtune command
The schedtune command allows you to specify the SCHED_R with the -r flag and
the SCHED_D with the -d flag. When executing the schedtune command without
flags, the current values will be shown:
# /usr/samples/kernel/schedtune
-h
SYS
0
THRASH
-p
-m
PROC MULTI
4
2
SUSP
-w
-e
WAIT GRACE
1
2
FORK
-f
-d
TICKS SCHED_D
10
16
SCHED
-r
-t
-s
SCHED_R TIMESLICE MAXSPIN
16
1
16384
CLOCK
-c
%usDELTA
100
Tuning is accomplished through two flags of the schedtune command: -r and -d.
Each flag specifies a parameter that is an integer from 0 to 32. The parameters
are applied by multiplying the recent CPU usage value by the parameter value
and then dividing by 32. The default SCHED_R and SCHED_D values are 16, as
seen in the previous output. The following sections discuss different uses of the
schedtune command.
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Schedtune example one
The following command will result in SCHED_R = 0 and SCHED_D = 0.5:
# /usr/samples/kernel/schedtune -r 0
This would mean that the CPU penalty was always 0, making priority absolute.
No background process would get any CPU time unless there were no
dispatchable foreground processes at all, as background processes in ksh are
started with adding 4 to the nice value of the parent shell. The priority values of
the threads would effectively be constant, although they would not technically be
fixed-priority threads.
Schedtune example two
The following command would result in an effective SCHED_R = 1 and
SCHED_D = 1:
# /usr/samples/kernel/schedtune -r 32 -d 32
This would mean that long-running threads would reach a C value of 120 and
remain there, contending on the basis of their nice values. New threads would
have priority, regardless of their nice value, until they had accumulated enough
time slices to bring them within the priority value range of the existing threads.
Schedtune example three
The most likely reason to manipulate the values would be to make sure that
background processes do not compete with foreground processes. By making
SCHED_R smaller, you can restrict the range of possible priority values. For
example:
# /usr/samples/kernel/schedtune -r 5
(SCHED_R = 0.15625, SCHED_D = 0.5) would mean that a foreground process
would never have to compete with a background process started with the
command nice -n 20. The limit of 120 CPU time slices accumulated would mean
that the maximum CPU penalty for the foreground process would be 18. In
Figure 6-4 on page 216, this relationship is graphically shown. Because the CPU
penalty will get a maximum value of 18, the foreground process with a nice value
of 20 will always, when it needs, get CPU. On the other hand, the background
process, with a nice value of 40, will use CPU only when the foreground process
does not need the CPU.
Chapter 6. Performance management tools
215
Figure 6-4 CPU penalty example
SCHED_R and SCHED_D guidelines
The following discusses guidelines for tuning performance using SCHED_R and
SCHED_D.
 Smaller values of SCHED_R narrow the priority range and the nice value has
more of an impact on the priority.
 Larger values of SCHED_R widen the priority range and the nice value has
less of an impact on the priority.
 Smaller values of SCHED_D decay CPU usage at a faster rate and can
cause CPU-intensive threads to be scheduled sooner.
 Larger values of SCHED_D decay CPU usage at a slower rate and penalize
CPU-intensive threads more (thus favoring interactive-type threads).
If you conclude that one or both parameters need to be modified to
accommodate your workload, you can enter the schedtune command while
logged on as root user. The changed values will persist until the next schedtune
command that modifies them, or until the next system boot. Values can be reset
216
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
to their defaults with the command schedtune -D, but remember that all
schedtune parameters are reset by that command, including VMM memory load
control parameters. To make a change to the parameters that will persist across
boots, add an appropriate line at the end of the /etc/inittab file (or in the AIX 5L
Version 5.2 /etc/tunables file.
VMM memory load control using schedtune
The VMM memory load control facility protects an overloaded system from
thrashing. For early versions of the operating system, if a large number of
processes hit the system at the same time, memory became overcommitted and
thrashing occurred, causing performance to degrade rapidly. A memory-load
control mechanism was developed that could detect thrashing. Certain
parameters affect the function of the load-control mechanism.
With the schedtune command, the root user can affect the criteria used to
determine thrashing, the criteria used to determine which processes to suspend,
the length of time to wait after thrashing ends before reactivating processes, the
minimum number of processes exempt from suspension, or reset values to the
defaults.
Scheduler tuning using schedtune
With the schedtune command you can change scheduler parameters at runtime,
and these changes will be cleared at the next reboot. If you find usefull settings
for the system, then run schedtune in rc.local. The average time slice of the
scheduler can be changed with the -tN parameter. The system uses 1 for N as
the default. Setting N to any other value will change the maximum number of
clock ticks between dispatches of processes. Usually the scheduler dispatches
processes once per clock interrupt (roughly every 10 ms), so the maximum time
a process can be active before the dispatcher tries to dispatch another one is 10
ms.
Other schedtune parameters enable you to set the delay before retrying a failed
fork function, to set the delay after thrashing before a process gets into the run
queue again, and to set how long a process has to be able to run before being
suspended.
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Note: The schedtune command is in the samples directory because it is very
VMM-implementation dependent. The schedtune code that accompanies each
release of the operating system is tailored specifically to the VMM in that
release. Running the schedtune command from one release on a different
release might result in an operating-system failure. It is also possible that the
functions of the schedtune command may change from release to release. Do
not propagate shell scripts or /etc/inittab entries that include the schedtune
command to a new release without checking the schedtune documentation for
the new release to make sure that the scripts will still have the desired effect.
The schedtune -? command provides a description of the flags and options. The
source and object code of the schedtune command are in /usr/samples/kernel.
The schedtune command summary
The schedtune command is used to manipulate the scheduler and the swapper.
There are some major differences between the commands in AIX Version 4.3.2
and AIX Version 4.3.3.
The syntax of the schedtune command is:
schedtune [ -D | { [ -d n ] [ -e n ] [ -f n ] [ -h n ] [ -m n ] [ -p n ]
[ -r n ] [ -t n ] [ -w n] } ]
Table 6-1 gives some useful schedtune flags from a CPU-tuning perspective.
Table 6-1 Commonly used flags of the schedtune command
Flag
Description
-r
Manipulates the SCHED_R weighting factor
-d
Manipulates the SCHED_D decay factor
-D
Resets all schedtune values to default values
6.3.2 The nice and renice commands
The nice value has been explained in “The nice and renice commands” on
page 15. The nice value can be seen with the ps command in the NI column:
$ ps -lu
F
200001
200001
200001
200001
218
thomasc
S
UID
PID PPID
C PRI NI ADDR
A 15610 5204 15476
3 61 20 a655
A 15610 15476 12948
1 60 20 5029
A 15610 15818 15476 120 126 24 408b
A 15610 16792 15476 120 126 24 e89e
SZ
344
488
44
44
TTY TIME CMD
pts/1 0:00 ps
pts/1 0:00 ksh
pts/1 0:25 tctest
pts/1 0:18 tctest
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Two programs have been started in the background, as shown by the nice value
of 24, while the ps command running in the foreground has a nice value of 20. All
outputs from the ps command have been edited in this to fit the screen.
Running a command with nice
Any user can run a command to set a less-favorable-than-normal priority by
using the nice command. Only the root user can use the nice command to run
commands at a more-favorable-than-normal priority. From the root user, the nice
command values range between -20 and 19.
With the nice command, the user specifies a value to be added to or subtracted
from the default nice value. The modified nice value is used for the process that
runs the specified command. The priority of the process is still non-fixed; that is,
the priority value is still recalculated periodically based on the CPU usage, nice
value, and minimum user-process-priority value.
The user thomasc, not being the root user, has the a range of nice values
between 1 and 19 available. When applying a nice value to a background
command, note that the maximum NI value is 39 even though the calculated
value would be 43 (34 + 9), as shown in the following example:
# id
uid=15610(thomasc) gid=0(system)
# nice -19 ./tprof.tctestprg &
# ps -al|head -1 ; ps -al |grep tctestprg
F S
UID
PID PPID
C PRI NI ADDR
200001 A 15610 14740 15490 90 126 39 5888
240001 A 15610 15818
1 90 118 24 408b
240001 A 15610 16792
1 89 118 24 e89e
SZ
44
44
44
TTY TIME CMD
pts/3 0:58 tctestprg
pts/1 51:02 tctestprg
pts/1 50:55 tctestprg
The root user has the possibility to lessen the nice value. Notice the syntax; the
first dash (-) is only an option marker, and the other dash tells the nice command
to subtract 15 from the default value of 24 (the process is started in the
background). For example:
# nice --15 ./tprof/tctestprg &
# ps -al|head -1 ; ps -al |grep tctestprg
F S
UID
PID PPID
C PRI NI ADDR
200001 A 15610 14740 15490 91 126 39 5888
240001 A 15610 15818
1 92 119 24 408b
200001 A 0
16304 12948 85 84 9 c0bb
240001 A 15610 16792
1 92 59 -- e89e
SZ TTY
TIME
CMD
44 pts/3 4:37 tctestprg
44 pts/1 54:41 tctestprg
44 pts/1 0:03 tctestprg
44 pts/1 54:34 tctestprg
Another way to use the nice command to get the same result as in the previous
example, is with the -n flag, as follows:
# nice -n -15 ./tprof/tctestprg &
Chapter 6. Performance management tools
219
It is actually only in this case, where root lessens the nice value, that a significant
change is seen in the priority value. In the preceding output, the values nice=39
and nice=24 generate similar priority values (PRI column), but process 16304,
started by root with nice=9, has a significant advantage with a priority value of
84.
The output also shows the scenario when a process is executed with a fixed
priority (PID 16792). In the PRI column, the set priority is shown to be - 59, and
the NI column shows no value. This can be done with the setpri subroutine. The
setpri subroutine sets the scheduling priority of all threads in a process to be a
constant.
Changing the nice value on a running thread
The renice command, which has a similar syntax as the nice command, allows
you to modify the nice value on a running process. The example from the
previous section is used. For example, subtract 5 from the actual value of 9. On
the tctestprg, root is running:
# renice -n -5 16304
# ps -al|head -1 ; ps -al |grep tctestprg
F
S
UID
PID PPID
C PRI NI ADDR
200001 A 15610 14740 15490 94 126 39 5888
240001 A 15610 15818
1 94 120 24 408b
200001 A
0 16304 12948 86 76 4 c0bb
240001 A 15610 16792
1 94 120 24 e89e
SZ TTY TIME CMD
44 pts/3 17:13 tctestprg
44 pts/1 67:17 tctestprg
44 pts/1 12:37 tctestprg
44 pts/1 67:10 tctestprg
The PID is used to identify which program (or more correctly which thread) is to
be manipulated.
The nice and renice commands summary
The nice and renice commands are used to manipulate the nice value for the
threads of a process.
The syntax of the nice command is:
nice [ - Increment| -n Increment ] Command [ Argument ... ]
Some commonly used nice flags are listed in Table 6-2.
Table 6-2 Commonly used flags of the nice command
220
Flags
Description
-increment
Increments a command's priority up or down, by specifying a positive
or negative number
-nincrement
Same as previous flag
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The syntax of the renice command is:
renice [ -n Increment ] [ -g | -p | -u ] ID ...
Some commonly used renice flags are listed in Table 6-2 on page 220.
Table 6-3 Commonly used flags of the renice command
Flags
Description
-n increment
Specifies the number to add to the nice value of the process.
The value of increment can only be a decimal integer from -20
to 20.
-u username user
numeric ID
Changes nice values for user.
Important: Do not manipulate the scheduler without a thorough
understanding of the mechanisms controlling the scheduler.
6.4 The bindprocessor command
The bindprocessor command binds or unbinds the kernel threads of a process
or it lists available processors. To bind or unbind threads, it requires two
parameters, as follows:
bindprocessor Process ProcessorNum
The process parameter is the process identifier of the process whose threads are
to be bound or unbound, and the ProcessorNum parameter is the logical
processor number of the processor to be used. If the ProcessorNum parameter
is omitted, the process is bound to a randomly selected processor.
A process itself is not bound, but rather its kernel threads are bound. Once kernel
threads are bound, they are always scheduled to run on the chosen processor,
unless they are later unbound. When a new thread is created, it has the same
bind properties as its creator. This applies to the initial thread in the new process
created by the fork subroutine: The new thread inherits the bind properties of the
thread that called the fork. When the exec subroutine is called, thread properties
are left unchanged.
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221
To check what processors are available, enter the following command:
# bindprocessor -q
The available processors are:
0 1 2 3
To bind process 16792 to processor 2, enter the following command:
# bindprocessor 16792 2
To check which process threads are bound to which processor, check the BND
column in the ps command output:
# ps -mo THREAD
USER
PID PPID
root 12948 12796
root 13704 12948
thomasc 15818
1
root 16304 12948
thomasc 16792
1
-
TID ST
- A
7283 S
- A
19391 R
- A
16077 R
- A
17843 R
- A
16357 R
CP PRI
0 60
0 60
3 61
3 61
79 112
79 112
77 72
77 72
79 112
79 112
SC F
TT BND COMMAND
1 240001 pts/1
- ksh
1
400
- 1 200001 pts/1
- ps -mo THREAD
1
0
- 0 240001 pts/1
-./tprof/tctestprg
0
0
- 0 200001 pts/1
-./tprof/tctestprg
0
0
- 0 240001 pts/1
2./tprof/tctestprg
0
0
2 -
6.5 The vmtune command
The vmtune command changes operational parameters of the Virtual Memory
Manager (VMM) and other AIX components. The command and source for
vmtune are found in the /usr/samples/kernel directory. It is installed with the
bos.adt.samples fileset.
The vmtune command syntax is as follows:
vmtune [ -b numfsbuf ] [ -B numpbuf ] [ -c numclust ] [ -f minfree ]
[ -F maxfree ] [ -k npskill ] [ -l lrubucket ] [ -M maxpin ] [ -N pd_npages ]
[ -p minperm ] [ -P maxperm ] [ -r minpgahead ] [ -R maxpgahead ]
[-u lvm_budcnt] [ -w npswarn ] [-W maxrandwrt]
An example of the vmtune command without any flags is shown in the following:
# /usr/samples/kernel/vmtune
vmtune: current values:
-p
-P
-r
-R
minperm maxperm minpgahead maxpgahead
26007
104028
2
8
-M
222
-w
-k
-c
-b
-f
minfree
120
-F
maxfree
128
-B
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
-N
-W
pd_npages maxrandwrt
524288
0
-u
-l
-d
maxpin npswarn npskill numclust numfsbufs hd_pbuf_cnt lvm_bufcnt lrubucket
defps
104851
4096
1024
1
93
80
9
131072
-s
sync_release_ilock
0
-n
nokillroot
0
-S
v_pinshm
0
number of valid memory pages = 131063
maximum pinable=80.0% of real memory
number of file memory pages = 102029
1
-h
strict_maxperm
0
maxperm=79.4% of real memory
minperm=19.8% of real memory
numperm=77.8% of real memory
The Virtual Memory Manager (VMM) maintains a list of free real-memory page
frames. These page frames are available to hold virtual-memory pages needed
to satisfy a page fault. When the number of pages on the free list falls below that
specified by the minfree parameter, the VMM begins to steal pages to add to the
free list. The VMM continues to steal pages until the free list has at least the
number of pages specified by the maxfree parameter.
If the number of file pages (permanent pages) in memory is less than the number
specified by the minperm parameter, the VMM steals frames from either
computational or file pages, regardless of re-page rates. If the number of file
pages is greater than the number specified by the maxperm parameter, the VMM
steals frames only from file pages. Between the two, the VMM normally steals
only file pages, but if the repage rate for file pages is higher than the repage rate
for computational pages, computational pages are stolen as well.
If a process appears to be reading sequentially from a file, the values specified
by the minpgahead parameter determine the number of pages to be read ahead
when the condition is first detected. The value specified by the maxpgahead
parameter sets the maximum number of pages that will be read ahead,
regardless of the number of preceding sequential reads.
The vmtune command can only be executed by root. Changes made by the
vmtune command last until the next reboot of the system. If a permanent change
in VMM parameters is needed, an appropriate vmtune command should be put in
/etc/inittab.
Table 6-4 on page 224 lists the flags and some of the limitations for the settings.
Chapter 6. Performance management tools
223
Table 6-4 Commonly used flags of the vmtune command
224
Flag
Description
-b numfsbuf
Specifies the number of file system bufstructs. The current default in
AIX Version 4 is 93 because it is dependent on the size of the
bufstruct. This value must be greater than 0. Increasing this value will
help write performance for very large write sizes (on devices that
support very fast writes). In order to enable this value, you must
unmount the file system, change the value, and then mount the
system again.
-B numpbuf
Controls the number of pbufs available to the LVM device driver.
pbufs are pinned memory buffers used to hold I/O requests related to
a journaled file system (JFS). On systems where large amounts of
sequential I/O occurs, this can result in I/O bottlenecks at the LVM
layer waiting for pbufs to be freed. In AIX Version 4, a single pbuf is
used for each sequential I/O request regardless of the number of
pages in that I/O. The maximum value is 128.
-c numclust
Specifies the number of 16 KB clusters processed by write behind.
The default value is 1. Values can be any integer above 0. Higher
number of clusters may result in larger sequential write performance
on devices that support very fast writes (RAID and so on). Setting the
value to a very high number, such as 500000, will essentially defeat
the write-behind algorithm. This can be beneficial in cases such as
database index creations, where pages that were written to are read
a short while later; write-behind could actually cause this process to
take longer. One suggestion is to turn off write-behind before building
indexes and then turn it back on after indexes have been built. For
example, the mkpasswd command can run significantly faster when
write-behind is disabled.
-f minfree
Specifies the minimum number of frames on the free list. This
number can range from 8 to 204800. The default value depends on
the amount of RAM on the system. minfree is by default the value of
maxfree: 8. The value of maxfree is equal to minimum (the number
of memory pages divided by 128). The delta between minfree and
maxfree should always be equal to or greater than maxpgahead.
-F maxfree
Specifies the number of frames on the free list at which page stealing
is to stop. This number can range from 16 to 204800, but must be
greater than the number specified by the minfree parameter by at
least the value of maxpgahead.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-k npskill
Specifies the number of free paging-space pages at which AIX
begins killing processes. The formula to determine the default value
of npskill in AIX Version 4 is:
MAX(64, number_of_paging_space_pages/128)
The npskill value must be greater than 0 and less than the total
number of paging space pages on the system. The default value is
128.
-l lrubucket
This parameter specifies the size (in 4 KB pages) of the least recently
used (LRU) page replacement bucket size. This is the number of
page frames that will be examined at one time for possible page outs
when a free frame is needed. A lower number will result in lower
latency when looking for a free frame but will also result in behavior
that is not as similar to a true LRU algorithm. The default value is 512
MB and the minimum is 256 MB. Tuning this option is not
recommended.
-M maxpin
Specifies the maximum percentage of real memory that can be
pinned. The default value is 80 percent. If this value is changed, the
new value should ensure that at least 4 MB of real memory will be left
unpinned for use by the kernel. maxpin values must be greater than
1 and less than 100. The value under maxpin is converted to a
percentage at the end of the output of vmtune.
-N pd_npages
Specifies the number of pages that should be deleted in one chunk
from RAM when a file is deleted. Changing this value may only be
beneficial to real-time applications that delete files. By reducing the
value of pd_npages, a real-time application can get better response
time since a fewer number of pages will be deleted before a process
or thread is dispatched. The default value is the largest possible file
size divided by the page size (currently 4096); if the largest possible
file size is 2 GB, then pd_npages is, by default, 524288.
-p minperm
Specifies the point below which file pages are protected from the
repage algorithm. This value is a percentage of the total real-memory
page frames in the system. The specified value must be greater than
or equal to 5. The default value of the minperm percentage is always
around 17–19 percent of memory.
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225
Flag
Description
-P maxperm
Specifies the point above which the page stealing algorithm steals
only file pages. This value is expressed as a percentage of the total
real-memory page frames in the system. The specified value must be
greater than or equal to 5.
The default value of the maxperm percentage is always around
75–80 percent of memory. A pure Network File System (NFS) server
may obtain better performance by increasing the maxperm value. A
system that accesses large files (over 50–75 percent of the amount
of RAM on the system; look at numperm to see how much memory
is currently used for file mapping) may benefit by increasing the
maxperm value. maxperm can be reduced on systems with large
active working storage requirements (the AVM column from vmstat
compared to total real page frames) to reduce or eliminate page
space I/O.
-r minpgahead
Specifies the number of pages with which sequential read-ahead
starts. This value can range from 0 to 4096. It should be a power of
2. The default value is 2.
-R
maxpgahead
Specifies the maximum number of pages to be read ahead. This
value can range from 0 to 4096. It should be a power of 2 and should
be greater than or equal to minpgahead. The default value is 8.
Increasing this number will help large sequential read performance.
Because of other limitations in the kernel and the Logical Volume
Manager (LVM), the maximum value should not be greater than 128.
The delta between minfree and maxfree should always be equal to or
greater than maxpgahead.
-u lvm_bufcnt
Specifies the number of LVM buffers for raw physical I/Os. The
default value is 9. The possible values can range between 1 and 64.
It may be beneficial to increase this value if you are doing large raw
I/Os (that is, not going through the JFS).
-w npswarn
Specifies the number of free paging-space pages at which AIX
begins sending the SIGDANGER signal to processes. The formula to
determine the default value is:
MAX(512, 4*npskill)
The value of npswarn must be greater than 0 and less than the total
number of paging space pages on the system. The default value is
512.
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Flag
Description
-W
maxrandwrt
Specifies a threshold (in 4 KB pages) for random writes to
accumulate in RAM before these pages are syncd to disk using a
write-behind algorithm. This threshold is on a per file basis. The -W
maxrandwrt option is only available in AIX Version 4.1.3 and later.
The default value of maxrandwrt is 0, which disables random
write-behind. By enabling random write-behind (a typical value might
be 128), applications that make heavy use of random writes can get
better performance due to less dependence on the sync daemon to
force writes out to disk. Some applications may degrade their
performance due to write-behind (such as database index creations).
In these cases, it may be beneficial to disable write-behind before
creating database indexes and then re-enabling write-behind after
the indexes are created.
6.6 Workload Manager (WLM)
WLM is designed to give system administrators more control over how the
scheduler and the virtual memory manager (VMM) allocate resources to
processes. This can be used to prevent different classes of jobs from interfering
with each other and to allocate resources based on the requirements of different
groups of users.
With WLM, you can create different classes of service for jobs, as well as specify
attributes for those classes. These attributes specify minimum and maximum
amounts of CPU, physical memory, and disk I/O throughput to be allocated to a
class. WLM then assigns jobs automatically to classes using class assignment
rules provided by a system administrator. These assignment rules are based on
the values of a set of attributes for a process. Either the system administrator or
a privileged user can also manually assign jobs to classes, overriding the
automatic assignment.
The system administrator can specify the properties for the WLM subsystem by
using either the Web-based System Manager graphical user interface, SMIT
ASCII-oriented interface, the WLM command line interface, or by creating flat
ASCII files. The Web-based System Manager and SMIT interfaces use the WLM
commands to record the information in the same flat ASCII files. These files are
named as follows:
classes
Class definitions
description
Configuration description text
limits
Class limits
shares
Class target shares
Chapter 6. Performance management tools
227
rules
Class assignment rules
These files are called the WLM property files. A set of WLM property files defines
a WLM configuration. You can create multiple sets of property files, defining
different configurations of workload management. These configurations are
located in subdirectories of /etc/wlm. The WLM property files describing the
superclasses of the Config configuration are the file's classes, description, limits,
shares, and rules in /etc/wlm/Config. Then, the property files describing the
subclasses of the superclass super of this configuration are the file's classes,
limits, shares and rules in directory /etc/wlm/Config/Super. Only the root user can
start or stop WLM, or switch from one configuration to another.
The command to submit the WLM property files, wlmcntrl, and the other WLM
commands allow users to specify an alternate directory name for the WLM
properties files. This allows you to change the WLM properties without altering
the default WLM property files.
A symbolic link, /etc/wlm/current, points to the directory containing the current
configuration files. Update this link with the wlmcntrl command when you start
WLM with a specified set of configuration files. The sample configuration files
shipped with the operating system are in /etc/wlm/standard.
WLM configuration is performed through the preferred interface, the Web-based
System Manager (Figure 6-5 on page 229), through a text editor and AIX
commands, or through the AIX administration tool SMIT.
228
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure 6-5 Web-based System Manager Overview and Tasks dialog
6.6.1 WLM concepts and architecture
The following section outlines the concepts provided with WLM on AIX 5L.
Classes
The central concept of WLM is the class. A class is a collection of processes
(jobs) that has a single set of resource limits applied to it. WLM assigns
processes to the various classes and controls the allocation of system resources
among the different classes. For this purpose, WLM uses class assignment rules
and per-class resource shares and limits set by the system administrator. The
resource entitlements and limits are enforced at the class level. This is a way of
defining classes of service and regulates the resource utilization of each class of
applications to prevent applications with very different resource utilization
patterns from interfering with each other when they are sharing a single server.
Hierarchy of classes
WLM allows system administrators to set up a hierarchy of classes with two
levels by defining superclasses and subclasses. In other words, a class can
Chapter 6. Performance management tools
229
either be a superclass or a subclass. The main difference between superclasses
and subclasses is the resource control (shares and limits):
 At the superclass level, the determination of resource entitlement (based on
the resource shares and limits) is based on the total amount of each resource
managed by WLM available on the machine.
 At the subclass level, the resource shares and limits are based on the amount
of each resource allocated to the parent superclass.
The system administrator (the root user) can delegate the administration of the
subclasses of each superclass to a superclass administrator (a non-root user),
thus allocating a portion of the system resources to each superclass and then
letting superclass administrators distribute the allocated resources among the
users and applications they manage.
WLM supports 32 superclasses (27 user defined plus five predefined). In turn,
each superclass can have 12 subclasses (10 user defined and two predefined,
as shown in Figure 6-6). Depending on the needs of the organization, a system
administrator can decide to use only superclasses or both superclasses and
subclasses. An administrator can also use subclasses only for some of the
superclasses.
Each class is given a name by the WLM administrator who creates it. A class
name can be up to 16 characters long and can only contain uppercase and
lowercase letters, numbers, and underscores (_). For a given WLM configuration,
the names of all the superclasses must be different from one another, and the
names of the subclasses of a given superclass must be different from one
another. Subclasses of different superclasses can have the same name. The
fully qualified name of a subclass is superclass_name.subclass_name.
In the remainder of this section, whenever the term class is used, it is applicable
to both subclasses and superclasses. The following subsections describe both
super- and subclasses in greater detail, as well as the backward compatibility
WLM provides to configurations of its first release.
Superclass
subclass
Superclass
subclass
Superclass
subclass
Figure 6-6 Hierarchy of classes
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Superclasses
A superclass is a class with subclasses associated with it. No process can
belong to the superclass without also belonging to a subclass, either predefined
or user defined. A superclass has a set of class assignment rules that determines
which processes will be assigned to it. A superclass also has a set of resource
limitation values and resource target shares that determine the amount of
resources that can be used by processes belonging to it. These resources will be
divided among the subclasses based on the resource limitation values and
resource target shares of the subclasses.
Up to 27 superclasses can be defined by the system administrator. In addition,
five superclasses are automatically created to deal with processes, memory, and
CPU allocation, as follows:
 Default superclass: The default superclass is named default and is always
defined. All non-root processes that are not automatically assigned to a
specific superclass will be assigned to the default superclass. Other
processes can also be assigned to the default superclass by providing
specific assignment rules.
 System superclass: This superclass has all privileged (root) processes
assigned to it if they are not assigned by rules to a specific class, plus the
pages belonging to all system memory segments, kernel processes, and
kernel threads. Other processes can also be assigned to the system
superclass. This default is for this superclass to have a memory minimum
limit of one percent.
 Shared superclass: This superclass receives all the memory pages that are
shared by processes in more than one superclass. This includes pages in
shared memory regions and pages in files that are used by processes in more
than one superclass (or in subclasses of different superclasses). Shared
memory and files used by multiple processes that belong to a single
superclass (or subclasses of the same superclass) are associated with that
superclass. The pages are placed in the shared superclass only when a
process from a different superclass accesses the shared memory region or
file. This superclass can have only physical memory shares and limits applied
to it. It cannot have shares or limits for the other resource types, subclasses,
or assignment rules specified. Whether a memory segment shared by the
processes in the different superclasses is classified into the shared
superclass, or remains in the superclass it was initially classified into depends
on the value of the localshm attribute of the superclass the segment was
initially classified into.
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 Unclassified superclass: The processes in existence at the time WLM is
started are classified according to the assignment rules of the WLM
configuration being loaded. During this initial classification, all the memory
pages attached to each process are charged either to the superclass the
process belongs to (when not shared, or shared by processes in the same
superclass) or to the shared superclass, when shared by processes in
different superclasses. However, there are a few pages that cannot be
directly tied to any processes (and thus to any class) at the time of this
classification, and this memory is charged to the unclassified superclass; for
example, pages from a file that has been closed. The file pages will remain in
memory, but no process owns these pages; therefore, they cannot be
charged to a specific class. Most of this memory will end up being correctly
reclassified over time, when it is either accessed by a process, or freed and
reallocated to a process after WLM is started. There are a few kernel
processes, such as wait or Irud, in the unclassified superclass. Even though
this superclass can have physical memory shares and limits applied to it,
WLM commands do not allow you to set shares and limits or specify
subclasses or assignment rules on this superclass.
 Unmanaged superclass: A special superclass named unmanaged will always
be defined. No processes will be assigned to this class. This class will be
used to accumulate the memory usage for all pinned pages in the system that
are not managed by WLM. The CPU utilization for the waitprocs is not
accumulated in any class. This is deliberate; otherwise, the system would
always seem to be at 100 percent CPU utilization, which could be misleading
for users when looking at the WLM or system statistics. This superclass can
not have shares or limits for any other resource types, subclasses, or
assignment rules specified.
Subclasses
A subclass is a class associated with exactly one superclass. Every process in
the subclass is also a member of the superclass. Subclasses only have access
to resources that are available to the superclass. A subclass has a set of class
assignment rules that determine which of the processes assigned to the
superclass will belong to it. A subclass also has a set of resource limitation
values and resource target shares that determine the resources that can be used
by processes in the subclass. These resource limitation values and resource
target shares indicate how much of the superclass’s target (the resources
available to the superclass) can be used by processes in the subclass.
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Up to 10 out of a total of 12 subclasses can be defined by the system
administrator or by the superclass administrator for each superclass. In addition,
two special subclasses, default and shared, are always defined in each
superclass as follows:
 Default subclass: The default subclass is named default and is always
defined. All processes that are not automatically assigned to a specific
subclass of the superclass will be assigned to the default subclass. You can
also assign other processes to the default subclass by providing specific
assignment rules.
 Shared subclass: This subclass receives all the memory pages used by
processes in more than one subclass of the superclass. This includes pages
in shared memory regions and pages in files that are used by processes in
more than one subclass of the same superclass. Shared memory and files
used by multiple processes that belong to a single subclass are associated
with that subclass. The pages are placed in the shared subclass of the
superclass only when a process from a different subclass of the same
superclass accesses the shared memory region or file. There are no
processes in the shared subclass. This subclass can only have physical
memory shares and limits applied to it. It cannot have shares or limits for the
other resource types or assignment rules specified.
Tiers
Tier configuration is based on the importance of a class relative to other classes
in WLM. There are 10 available tiers from 0 through to 9. Tier value 0 is the most
important and value 9 is the least important. As a result, classes belonging to tier
0 will get resource allocation priority over classes in tier 1, classes in tier 1 will
have priority over classes in tier 2, and so on. The default tier number, if the
attribute is not specified, is 0.
The tier applies at both the superclass and subclass levels. Superclass tiers are
used to specify resource allocation priority between superclasses, and subclass
tiers are used to specify resource allocation priority between subclasses of the
same superclass. There is no relationship between tier numbers of subclasses of
different superclasses.
Tier separation, in terms of prioritization, is much more enforced in AIX 5L than in
the previous release. A process in tier 1 will never have priority over a process in
tier 0, since there is no overlapping of priorities in tiers. It is unlikely that classes
in tier 1 will acquire any resources if the processes in tier 0 are consuming all the
resources. This occurs because the control of leftover resources is much more
restricted than in the AIX Version 4.3.3 release of WLM, as shown in Figure 6-7
on page 234.
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Excess resources
cascade down
to next tier
Tier 0
Tier 1
Tier 2
Figure 6-7 Resources cascading through tiers
Class attributes
In order to create a class, there are different attributes that are needed to have
an accurate and well-organized group of classes. Figure 6-8 shows the SMIT
panel for class attributes.
Figure 6-8 SMIT with the class creation attributes screen
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The sequence of attributes within a class (as shown in Figure 6-8 on page 234) is
outlined below:
 Class name
A unique class name with up to 16 characters. It can contain uppercase and
lowercase letters, numbers, and underscores (_).
 Description
An optional brief description about this class.
 Tier
A number between 0 and 9, for class priority ranking. It will be the tier that this
class will belong to. An explanation about tiers can be found in “Tiers” on
page 233.
 Resource set
This attribute is used to limit the set of resources a given class has access to
in terms of CPUs (processor set). The default, if unspecified, is system, which
gives access to all the CPU resources available on the system.
 Inheritance
The inheritance attribute indicates whether a child process should inherit its
parent’s class or get classified according to the automatic assignment rules
upon exec. The possible values are yes or no; the default is no. This attribute
can be specified at both superclass and subclass level.
 User and group authorized to assign its processes to this class
These attributes are valid for all the classes. They are used to specify the
user name and the group name of the user or group authorized to manually
assign processes to the class. When manually assigning a process (or a
group of processes) to a superclass, the assignment rules for the superclass
are used to determine which subclass of the superclass each process will be
assigned to.
 User and group authorized to administer this class
These attributes are valid only for superclasses. They are used to delegate
the superclass administration to a user and group of users.
 Localchm
Specifies whether memory segments that are accessed by processes in
different classes remain local to the class they were initially assigned to, or if
they go to the shared class.
Segment authorization to migrate to the shared class
With Workload Manager in earlier versions of AIX, whenever a memory segment
is accessed by processes from different classes, the segment is reclassified as
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shared. This occurs because one of the classes sharing the memory segment
would otherwise be penalized as the user of this resource while the others are
not. The consequence of the segment moving to shared is that users partially
lose control of it. In AIX 5L, an attribute has been added at the class level to avert
the automatic reclassification of the class. This attribute, localshm, if set to no,
allows the segment to be reclassified to the shared class. If it is set to yes, then it
is not reclassified. From the command line, the command will be similar to that
shown in the example below:
# mkclass -a tier=2 -a adminuser=wlmu6 -a localshm=yes -c shares=2\
-m shares=3 -d new_config super3
From the SMIT panels, general characteristics of a class panel will have the
localshm option, as in the example shown in Figure 6-9.
Figure 6-9 SMIT panel shows the additional localshm attribute
Classification process
There are two ways to classify processes in WLM:
 Automatic assignment when a process calls the system call exec, using
assignment rules specified by a WLM administrator. This automatic
assignment is always in effect (cannot be turned off) when WLM is active.
This is the most common method of assigning processes to the different
classes.
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 Manual assignment of a selected process or group of processes to a class by
a user with the required authority on both the process and the target class.
This manual assignment can be done either by a WLM command, which
could be invoked directly or through SMIT or Web-based System Manager, or
by an application, using a function of the WLM Application Programming
Interface. Manual assignment overrides automatic assignment.
6.6.2 Automatic assignment
The automatic assignment of processes to classes uses a set of class
assignment rules specified by a WLM administrator. There are two levels of
assignment rules:
 A set of assignment rules at the WLM configuration level used to determine
which superclass a given process should be assigned to.
 A set of assignment rules at the superclass level used to determine which
subclass of the superclass the process should be assigned to.
The assignment rules at both levels have exactly the same format.
When a process is created by fork, it remains in the same class as its parent.
Usually, reclassification happens when the new process calls the system call
exec. In order to classify the process, WLM starts by examining the top level
rules list for the active configuration to find out which superclass the process
should belong to. For this purpose, WLM takes the rules one at a time, in the
order they appear in the file, and checks the current values for the process
attributes against the values and lists of values specified in the rule. When a
match is found, the process will be assigned to the superclass named in the first
field of the rule. Then the rules list for the superclass is examined in the same
way to determine which subclass of the superclass the process should be
assigned to. For a process to match one of the rules, each of its attributes must
match the corresponding field in the rule. The rules to determine whether the
value of a process attribute matches the values in the field of the rules list are as
follows:
 If the field in the rule has a value of hyphen (-), any value of the
corresponding process attribute is a match.
 If the value of the process attribute (for all the attributes except type) matches
one of the values in the list in a rule, and it is not excluded (prefaced by an
exclamation point (!)), it is considered a match.
 When one of the values for the type attribute in the rule is comprised of two or
more values separated by a plus (+) sign, a process will be a match for this
value only if its characteristics match all the values mentioned above.
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As previously mentioned, at both superclass and subclass levels, WLM goes
through the rules in the order in which they appear in the rules list, and classifies
the process in the class corresponding to the first rule for which the process is a
match. This means that the order of the rules in the rules list is extremely
important, and caution must be applied when modifying it in any way.
6.6.3 Manual assignment
Manual assignment is a feature introduced in AIX 5L WLM. It allows system
administrators and applications to override, at any time, the traditional WLM
automatic assignment (processes’ automatic classification based on class
assignment rules) and force a process to be classified in a specific class.
The manual assignment can be made or canceled separately at the superclass
level, the subclass level, or both. In order to manually assign processes to a
class or cancel an existing manual assignment, a user must have the right level
of privilege (that is, must be the root user, adminuser, or admingroup for the
superclass or authuser and authgroup for the superclass or subclass). A process
can be manually assigned to a superclass only, a subclass only, or to a
superclass and a subclass of the superclass. In the latter case, the dual
assignment can be done simultaneously (with a single command or API call) or at
different times, possibly by different users.
A manual assignment will remain in effect (and a process will remain in its
manually assigned class) until:
 The process terminates.
 WLM is stopped. When WLM is restarted, the manual assignments in effect
when WLM was stopped are lost.
 The class the process has been assigned to is deleted.
 A new manual assignment overrides a prior one.
 The manual assignment for the process is canceled.
In order to assign a process to a class or cancel a prior manual assignment, the
user must have authority both on the process and on the target class. These
constraints translate into the following:
 The root user can assign any process to any class.
 A user with administration privileges on the subclasses of a given superclass
(that is, the user or group name matches the attributes adminuser or
admingroup of the superclass) can manually reassign any process from one
of the subclasses of this superclass to another subclass of the superclass.
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 A user can manually assign their own processes (same real or effective user
ID) to a superclass or a subclass for which they have manual assignment
privileges (that is, the user or group name matches the attributes authuser or
authgroup of the superclass or subclass).
This defines three levels of privilege among the persons who can manually
assign processes to classes, root being the highest. In order for a user to modify
or cancel a manual assignment, the user must be at the same or higher level of
privilege as the person who issued the last manual assignment.
Class assignment rules
After the definition of a class, it is time to set up the class assignment rules so
that WLM can perform its automatic assignment. The assignment rules are used
by WLM to assign a process to a class based on the user, group, application path
name, type of process, and application tag, or a combination of these five
attributes.
The next sections describe the attributes that constitute a class assignment rule.
All these attributes can contain a hyphen, which means that this field will not be
considered when assigning classes to a process.
Class name
This field must contain the name of a class that is defined in the class file
corresponding to the level of the rules file we are configuring (either superclass
or subclass). Class names can contain only uppercase and lowercase letters,
numbers, and underscores (_), and can be up to 16 characters in length. No
assignment rule can be specified for the system-defined classes unclassified,
unmanaged , and shared.
Reserved
Reserved for future use. Its value must be a hyphen, and it must be present in
the rule.
User
The user name (as specified in the /etc/passwd file, LDAP, or in NIS) of the user
owning a process can be used to determine the class to which the process
belongs. This attribute is a list of one or more user names, separated by a
comma. Users can be excluded by using an exclamation point prefix. Patterns
can be specified to match a set of user names using full Korn shell pattern
matching syntax.
Applications that use the setuid permission to change the effective user ID they
run under are still classified according to the user that invoked them. The
processes are only reclassified if the change is done to the real user ID (UID).
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Group
The group name (as specified in the /etc/group file, LDAP, or in NIS) of a process
can be used to determine the class to which the process belongs. This attribute
is a list composed of one or more groups, separated by a comma. Groups can be
excluded by using an exclamation point prefix. Patterns can be specified to
match a set of group names using full Korn shell pattern matching syntax.
Applications that use the setgid permission to change the effective group ID they
run under are still classified according to the group that invoked them. The
processes are only reclassified if the change is done to the real group ID (GID).
Application path names
The full path name of the application for a process can be used to determine the
class to which a process belongs. This attribute is a list composed of one or more
applications, separated by a comma. The application path names will be either
full path names or Korn shell patterns that match path names. Application path
names can be excluded by using an exclamation point prefix.
Process type
In AIX 5L, the process type attribute is introduced as one of the ways to
determine the class to which a process belongs. This attribute consists of a
comma-separated list, with one or more combinations of values, separated by a
plus sign (+). A plus sign provides a Boolean and function, and a comma
provides a logical or function. Table 6-5 provides a list of process types that can
be used. (Note: 32bit and 64bit are mutually exclusive.)
Table 6-5 List of process types
Attribute value
Process type
32bit
The process is a 32-bit process.
64bit
The process is a 64-bit process.
plock
The process called plock() to pin memory.
fixed
The process has a fixed priority (SCHED_FIFO or SCHED_RR).
Application tags
In AIX 5L, the application tag attribute is introduced as one of the forms of
determining the class to which a process belongs. This is an attribute meant to
be set by WLM’s API as a way to further extend the process classification
possibilities. This process was created to allow differentiated classification for
different instances of the same application. This attribute can have one or more
application tags, separated by commas. An application tag is a string of up to 30
alphanumeric characters.
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The classification is done by comparing the value of the attributes of the process
at exec time against the lists of class assignment rules to determine which rule is
a match for the current value of the process attributes. The class assignment is
done by WLM:
 When WLM is started for all the processes existing at that time.
 Every time a process calls the system calls exec, setuid (and related calls),
setgid (and related calls), setpri, and plock, once WLM is started.
There are two default rules that are always defined (that is, hardwired in WLM).
These are the default rules that assign all processes started by the user root to
the system class, and all other processes to the default class. If WLM does not
find a match in the assignment rules list for a process, these two rules will be
applied (the rule for system first), and the process will go to either system (UID
root) or default. These default rules are the only assignment rules in the standard
configuration installed with AIX.
Table 6-6 is an example of classes with their respective attributes for assignment
rules.
Table 6-6 Examples of class assignment rules
Class
Reserved
User
Group
Application
Type
Tag
System
-
root
-
-
-
-
db1
-
-
-
/usr/oracle/bin/db*
-
_db1
db2
-
-
-
/usr/oracle/bin/db*
-
_db2
devlt
-
-
dev
-
32bit
-
VPs
-
bob,!ted
-
-
-
-
acctg
-
-
acct*
-
-
-
In Table 6-6 the rule for default class is omitted from display, though this class’s
rule is always present in the configuration. The rule for system is explicit, and has
been put first in the file. This is deliberate so that all processes started by root will
be assigned to the system superclass. By moving the rule for the system
superclass further down in the rules file, the system administrator could have
chosen to assign the root processes that would not be assigned to another class
(because of the application executed, for example) to system only. In Table 6-6,
with the rule for system on top, if root executes a program in /usr/oracle/bin/db*
set, the process will be classified as system. If the rule for the system class were
after the rule for the db2 class, the same process would be classified as db1 or
db2, depending on the tag.
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These examples show that the order of the rules in the assignment rules file is
very important. The more specific assignment rules should appear first in the
rules file, and the more general rules should appear last. An extreme example
would be putting the default assignment rule for the default class, for which every
process is a match, first in the rules file. That would cause every process to be
assigned to the default class (the other rules would, in effect, be ignored).
You can define multiple assignment rules for any given class. You can also
define your own specific assignment rules for the system or default classes. The
default rules mentioned previously for these classes would still be applied to
processes that would not be classified using any of the explicit rules.
6.6.4 Backward compatibility
As mentioned earlier, in the first release of WLM, the system default for the
resource shares was one share. In AIX 5L, it is -, which means that the resource
consumption of the class for this particular resource is not regulated by WLM.
This changes the semantics quite a bit, and it is advisable that system
administrators review their existing configurations and consider if the new default
is good for their classes, or if they would be better off either setting up a default of
one share (going back to the previous behavior) or setting explicit values for
some of the classes.
In terms of limits, the first release of WLM only had one maximum, not two. This
maximum limit was in fact a soft limit for CPU and a hard limit for memory. Limits
specified for the old format, min percent-max percent, will have, in AIX 5L, the
max interpreted as a softmax for CPU and both values of hardmax and softmax
for memory. All interfaces (SMIT, AIX commands, and Web-based System
Manager) will convert all data existing from its old format to the new one.
The disk I/O resource is new for the current version, so when activating the AIX
5L WLM with the configuration files of the first WLM release, the values for the
shares and the limits will be the default ones for this resource. The system
defaults are:
 shares =  min = 0 percent, softmax = 100 percent, hardmax = 100 percent
For existing WLM configurations, the disk I/O resource will not be regulated by
WLM, which should lead to the same behavior for the class as with the first
version.
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6.6.5 Resource sets
WLM uses the concept of resource sets (or rsets) to restrict the processes in a
given class to a subset of the system's physical resources. In AIX 5L, the
physical resources managed are the memory and the processors. A valid
resource set is composed of memory and at least one processor.
Figure 6-10 shows the SMIT panel where a resource set can be specified for a
specific class.
Figure 6-10 Resource set definition for a specific class
By default, the system creates one resource set for all physical memory, one for
all CPUs, and one separate set for each individual CPU in the system. The
lsrset command lists all resource sets defined. A sample output for the lsrset
command follows:
# lsrset -av
T Name
Owner
Group
Mode
CPU Memory Resources
r sys/sys0
root
system r----4
511 sys/sys0
sys/node.00000 sys/mem.00000 sys/cpu.00003 sys/cpu.00002 sys/cpu.00001
sys/cpu.00000
r sys/node.00000
root
system r----4
511 sys/sys0
sys/node.00000 sys/mem.00000 sys/cpu.00003 sys/cpu.00002 sys/cpu.00001
sys/cpu.00000
r sys/mem.00000
root
system r----0
511 sys/mem.00000
r sys/cpu.00003
root
system r----1
0 sys/cpu.00003
r sys/cpu.00002
root
system r----1
0 sys/cpu.00002
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r
r
sys/cpu.00001
sys/cpu.00000
root
root
system
system
r----r-----
1
1
0
0
sys/cpu.00001
sys/cpu.00000
6.6.6 Rset registry
As mentioned previously, some resource sets in AIX 5L are created, by default,
for memory and CPU. It is possible to create different resource sets by grouping
two or more resource sets and storing the definition in the rset registry.
The rset registry services enable system administrators to define and name
resource sets so that they can then be used by other users or applications. In
order to alleviate the risks of name collisions, the registry supports a two-level
naming scheme. The name of a resource set takes the form
name_space/rset_name. Both the namespace and rset_name may each be 255
characters in size, are case-sensitive, and may contain only upper and lower
case letters, numbers, underscores, and periods. The namespace of sys is
reserved by the operating system and used for rset definitions that represent the
resources of the system.
The SMIT rset command has options to list, remove, or show a specific resource
set used by a process and the management tools, as shown in Figure 6-11.
Figure 6-11 SMIT main panel for resource set management
To create, delete, or change a resource set in the rset registry, you must select
the Manage Resource Set Database item in the SMIT panel. In this panel, it is
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also possible to reload the rset registry definitions to make all changes available
to the system. Figure 6-12 shows the SMIT panel for rset registry management.
Figure 6-12 SMIT panel for rset registry management
To add a new resource set, you must specify a name space, a resource set
name, and the list of resources. It is also possible to change the permissions for
the owner and group of this rset. In addition, permissions for the owner, groups,
and others can also be specified. Figure 6-13 on page 246 shows the SMIT
panel for this task.
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Figure 6-13 SMIT panel to add a new resource set
Whenever a new rset is created, deleted, or modified, a reload in the rset
database is needed in order to make the changes effective.
After a WLM configuration has been defined by the system administrator, it can
be made the active configuration using the wlmcntrl command. For example, to
starts WLM in active mode, enter:
# wlmcntrl -a
To validate if WLM is running, enter:
# wlmcntrl -q
1495-052 WLM is running
To stop WLM, enter:
# wlmcntrl -o
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6.7 Quiz
The following assessment questions help verify your understanding of the topics
discussed in this chapter.
1. Which of the following should be implemented to balance available
CPU/memory resources between applications?
A.
Loadleveler
B.
Nice/renice
C. Resource Manager
D.
Workload Manager
2. A nice value for a process is shown as 80 in a ps listing. Which command is
used to change this to a value of 100?
A.
renice 100 PID
B.
renice -n 20 PID
C. renice -20 PID
D.
renice -n -100 PID
3. Which command changes operational parameters of the Virtual Memory
Manager (VMM)?
A.
nice
B.
renice
C.
schedtune
D.
vmtune
4. Which of the following options is true regarding schedtune memory-load
control?
A.
Memory-load control is intended to smooth out infrequent peaks in load
that might otherwise cause a system to thrash. It is not intended to act
continuously in a configuration that has too little RAM to handle its normal
workload.
B.
Memory-load control cannot be turned off. Other parameters can be used
to control thrashing, like schedtune -D.
C. The AIX scheduler performs memory-load control by suspending
processes when memory is overcommitted. The system then swaps out
processes.
D.
Memory is considered overcommitted when the number of pages written
to paging space in the last second, multiplied by the value of the -h
parameter, is less than the number of page steals in the last second.
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5. Which of the following WLM files do not contain data directly related to
performance tuning?
A.
/etc/wlm/current/classes
B.
/etc/wlm/current/rules
C. /etc/wlm/current/limits
D.
/etc/wlm/current/shares
6.7.1 Answers
The following are the preferred answers to the questions provided in this section.
1. D
2. B
3. D
4. A
5. B
6.8 Exercise
The following exercises provide sample topics for self study. They will help
ensure comprehension of this chapter.
1. Find a process with a recent high CPU usage value. Use the renice
command to lessen its priority value. Follow the process CPU utilization.
Restore the nice value.
2. On a test system, manipulate the SCHED_R value to prioritize foreground
processes (for reference, see Figure 6-4 on page 216). Restore the default
values.
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7
Chapter 7.
Performance scenario
walkthroughs
This chapter provides a set of scenarios that allow you to better understand the
relationship between the tools, their output, and a problem you may need to
solve.
© Copyright IBM Corp. 2002. All rights reserved.
249
7.1 CPU performance scenario
In this section, a basic CPU-bound performance problem scenario is shown, with
conclusions made based on output from commands previously discussed in this
publication.
7.1.1 Data collection
The environment consists of a 2-way F50 with 50 Netstation clients connected
over Ethernet. Users are using an HTML application as an interface to a
database. Now the users are complaining about long response times. When
starting a browser window on a Netstation, the start up seems slow. To verify
this, the browser startup is executed with the time command:
# time netscape
real
user
sys
0m16.73s
0m0.83s
0m0.63s
By running time netscape, you can verify that the start up was slow. The normal
start up time of a browser in the example system would be under 10 seconds.
From the output, it seems that the systems waits for more than 15 seconds (user
+ sys = 1.46 seconds out of 16.73 seconds total time). In most cases systems
wait for I/O, so you run iostat:
tty:
tin
0.0
Disks:
hdisk0
hdisk1
hdisk2
hdisk3
cd0
tty:
Disks:
hdisk0
hdisk1
hdisk2
hdisk3
cd0
250
tout
328.5
% tm_act
0.0
0.0
0.0
0.0
0.0
tin
0.0
tout
332.1
% tm_act
0.0
0.0
0.0
0.0
0.0
avg-cpu:
Kbps
0.0
0.0
0.0
0.0
0.0
avg-cpu:
Kbps
0.0
0.0
0.0
0.0
0.0
% user
100.0
tps
0.0
0.0
0.0
0.0
0.0
Kb_read
0
0
0
0
0
% user
100.0
tps
0.0
0.0
0.0
0.0
0.0
% sys
0.0
% iowait
0.0
Kb_wrtn
0
0
0
0
0
% sys
0.0
Kb_read
0
0
0
0
0
% idle
0.0
% idle
0.0
Kb_wrtn
0
0
0
0
0
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
% iowait
0.0
There is no activity against the disks, but the %user shows 100.0. (This is an
extreme manufactured, although not edited, example). The problem is probably
CPU related. Next you would likely check the run queue with the vmstat
command:
# vmstat 2 5
kthr
memory
page
faults
----- ----------- ------------------------ -----------r b
avm
fre re pi po fr
sr cy in
sy cs
0 0 17354 15755
0
0
0
0
0
0 101
10
7
5 1 17354 15754
0
0
0
0
0
0 407 2228 101
5 1 17354 15752
0
0
0
0
0
0 413
43 93
5 1 17354 15752
0
0
0
0
0
0 405
43 92
5 1 17354 15752
0
0
0
0
0
0 407
42 90
cpu
----------us sy id wa
63 0 37 0
99 0 0 0
99 0 0 0
99 0 0 0
99 0 0 0
7.1.2 Data analysis
Five jobs on the run queue is not a normal state for this system. The next step
would be to find out what processes are causing the problems. This can be done
with the ps command:
# ps -ef |sort +3 -r |head -15
UID
PID PPID
C
STIME
TTY TIME CMD
thomasc 15860 12948 93 10:30:49 pts/1 17:41 ./tcprg5
thomasc 16312 12948 93 10:30:39 pts/1 20:30 ./tcprg3
thomasc 15234 12948 92 10:31:13 pts/1 15:21 ./tcprg1
thomasc 16844 12948 87 10:31:00 pts/1 13:15 ./tcprg2
thomasc 17420 12948 31 10:30:26 pts/1 14:53 ./tcprg4
root 14778 3420
4 10:51:10 pts/3 0:00 ps -ef
root 17154 3420
1 10:51:10 pts/3 0:00 sort +3 -r
root 13676 15080
0 15:54:12 pts/5 0:00 ksh
root 15080
1
0 15:54:11
- 0:00 xterm
root 4980
1
0 15:37:42
- 0:00 /usr/lib/errdemon -s 2000000
root 16510 3420
0 10:51:10 pts/3 0:00 head -15
root 16022 10872
0
Jun 29
lft0 7:05 topas n
root 3420 5568
0
Jun 28 pts/3 0:00 ksh
root 12948 12796
0
Jun 28 pts/1 0:02 ksh
# ps auxwww |head -14
USER
PID %CPU %MEM
SZ RSS
TTY STAT
STIME TIME COMMAND
thomasc 16312 25.0 0.0
44
64 pts/1 A
10:30:39 26:28 ./tcprg3
root
516 24.0 3.0 264 15396
- A
Jun 28 9544:43 kproc
thomasc 15860 20.7 0.0
44
64 pts/1 A
10:30:49 21:49 ./tcprg5
thomasc 15234 20.6 0.0
44
60 pts/1 A
10:31:13 21:20 ./tcprg1
thomasc 16844 18.4 0.0
44
64 pts/1 A
10:31:00 19:13 ./tcprg2
thomasc 17420 15.7 0.0
44
64 pts/1 A
10:30:26 16:44 ./tcprg4
root
1032 6.7 3.0 264 15396
- A
Jun 28 2679:27 kproc
root
1290 3.2 3.0 264 15396
- A
Jun 28 1263:12 kproc
root
774 3.2 3.0 264 15396
- A
Jun 28 1258:58 kproc
root
3158 0.0 0.0 356 384
- A Jun 28 8:27/usr/sbin/syncd 60
Chapter 7. Performance scenario walkthroughs
251
root
root
root
16022
2064
0
0.0
0.0
0.0
0.0
3.0
3.0
488 640
320 15452
268 15400
lft0 A
- A
- A
Jun 29 7:05 topas n
Jun 28 2:38 kproc
Jun 28 1:26 swapper
One user, thomasc, has started five programs with the prefix tcprg that has
accumulated a lot of recent CPU usage (C column). When looking at the -u flag
output from the ps command, the %CPU (reporting how much a process has
used CPU since started), these test programs use abnormally high CPU.
7.1.3 Recommendation
There are several ways to reverse the overload (kill PID, for example), but the
proper thing would be to check with the user thomasc and ask some questions,
such as “What are these process?” “Why are they running. Can they be
stopped?” “Do they have to run now. Can they be rescheduled?” Rescheduling
these kind of CPU consuming processes to a less busy time will probably give
the most significant advantage in performance.
If these processes can be rescheduled, this can be done with the batch
command, the at command, or by starting them from the crontab. Remember to
start such jobs at times when they are not in conflict with OLTPs.
If they have to run during a busy time, and to be running at times in the future,
some changes need to be done to improve the balance the performance of the
system. A recommendation is to move these test programs to a test system,
excluded from the production environment.
Another solution is to buy more CPUs, which is a good step if the hardware can
accommodate this, but may move the bottleneck to another resource of the
system, for example, memory.
Resource capping could be a solution, and for that there is no better way than
Workload Manager (WLM). For more information on WLM, see AIX 5L Workload
Manager (WLM), SG24-5977.
7.2 I/O performance scenario
In this scenario, a user reports that the month-end report is taking a long time to
run and the user is unsure what is causing this. One possible reason for this
report taking so long is that when AIX creates a print job the job is first written to
the print spooler. This spool file is created on the disk in /var/adm/spool. If there
is an I/O problem where the system is waiting for disk, then this file can take a
long time to generate, especially if it is a large file.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
7.2.1 Data collection
In this section, the outputs of the system are gathered by the vmstat and iostat
commands.
Below is the output of the iostat command for this system.
# iostat 1 10
tty:
tin
0.9
Disks:
hdisk0
hdisk1
cd0
tty:
% tm_act
19.4
49.0
0.0
tin
1.0
Disks:
hdisk0
hdisk1
cd0
tty:
tin
1.0
tin
2.0
Disks:
hdisk0
hdisk1
cd0
tty:
Disks:
hdisk0
hdisk1
cd0
tout
58.0
% tm_act
18.0
100.0
0.0
tin
2.0
Kbps
208.0
1552.0
0.0
tout
94.0
% tm_act
18.0
98.0
0.0
avg-cpu:
avg-cpu:
Kbps
232.0
808.0
0.0
0
1656
0
% sys
6.0
Kb_read
4
316
0
% user
0.0
tps
28.0
111.0
0.0
% sys
6.0
Kb_read
0
672
0
% user
0.0
tps
21.0
114.0
0.0
% sys
12.0
Kb_read
% user
0.0
tps
50.0
111.0
0.0
% sys
20.1
Kb_read
870967
1267281
0
% user
0.0
tps
101.0
108.0
0.0
avg-cpu:
Kbps
660.0
1108.0
0.0
% user
2.7
tps
32.3
52.9
0.0
avg-cpu:
Kbps
1616.0
2164.0
0.0
tout
58.0
% tm_act
25.0
100.0
0.0
avg-cpu:
Kbps
350.9
616.6
0.0
tout
0.0
% tm_act
29.0
100.0
0.0
Disks:
hdisk0
hdisk1
cd0
tty:
tout
52.6
% sys
12.0
Kb_read
0
312
0
% idle
43.3
% iowait
33.9
Kb_wrtn
921096
1881244
0
% idle
0.0
% iowait
88.0
Kb_wrtn
1616
508
0
% idle
0.0
% iowait
94.0
Kb_wrtn
660
436
0
% idle
0.0
% iowait
94.0
Kb_wrtn
204
1236
0
% idle
0.0
% iowait
88.0
Kb_wrtn
232
496
0
Chapter 7. Performance scenario walkthroughs
253
tty:
tin
1.0
Disks:
hdisk0
hdisk1
cd0
tty:
% tm_act
12.0
100.0
0.0
tin
2.0
Disks:
hdisk0
hdisk1
cd0
tty:
tin
2.0
tin
1.0
Disks:
hdisk0
hdisk1
cd0
tty:
Disks:
hdisk0
hdisk1
cd0
tout
1.0
% tm_act
8.9
100.0
0.0
tin
11.0
Kbps
67.3
3655.4
0.0
tout
11.0
% tm_act
23.0
100.0
0.0
avg-cpu:
tps
13.9
127.7
0.0
avg-cpu:
Kbps
200.0
744.0
0.0
% user
0.0
tps
23.0
102.0
0.0
% idle
0.0
% idle
0.0
% idle
0.0
% iowait
79.2
Kb_wrtn
64
3556
0
% idle
0.0
Kb_wrtn
200
468
0
Below is the output of the system using the vmstat command:
# vmstat 1 10
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 19776
121
0
1 82 225 594
0 208 658 160 3 20 43 34
0 2 19776
115
0
0
0 408 911
0 338 1160 327 0 9 0 91
0 3 19776
121
0
0
0 410 950
0 329 971 300 0 12 0 88
254
% iowait
87.0
Kb_wrtn
184
1484
0
% sys
6.0
Kb_read
0
276
0
% iowait
91.0
Kb_wrtn
216
588
0
% sys
20.8
Kb_read
4
136
0
% iowait
94.0
Kb_wrtn
76
616
0
% sys
13.0
Kb_read
0
244
0
% user
0.0
% idle
0.0
% sys
9.0
Kb_read
0
328
0
% user
0.0
tps
19.0
120.0
0.0
% sys
6.0
Kb_read
4
188
0
% user
0.0
tps
21.0
103.0
0.0
avg-cpu:
Kbps
184.0
1728.0
0.0
% user
0.0
tps
20.0
105.0
0.0
avg-cpu:
Kbps
216.0
916.0
0.0
tout
48.0
% tm_act
18.0
99.0
0.0
avg-cpu:
Kbps
80.0
804.0
0.0
tout
94.0
% tm_act
17.0
100.0
0.0
Disks:
hdisk0
hdisk1
cd0
tty:
tout
47.0
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
% iowait
94.0
0
0
0
0
0
0
0
3
3
3
2
3
3
3
19776
19776
19776
19776
19776
19776
19776
121
120
119
118
121
123
123
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 337 724
0 562 1136
0 632 1360
0 641 1366
0 1075 3353
0 761 1700
0 1170 1819
0
0
0
0
0
0
0
335
341
349
359
362
367
435
950
1279
1230
1630
2147
1225
1374
360
256
247
281
322
376
390
0
0
1
0
0
3
0
9
19
11
19
23
11
21
0
0
0
0
0
0
0
91
81
88
81
77
86
79
7.2.2 Data analysis
In this section, the key indicators of the output will be looked at and an
explanation given regarding the output.
The vmstat command output investigation
Although the vmstat command is a memory diagnostic tool, it does display one
I/O column. Notice the cpu column with the wa output; the output is on average
85 percent (add the column, excluding the first line, and divide by nine). If the wa
value is higher than 25 percent, it may indicate a problem with the disk
subsystem.
The high wa value leads you to two additional columns. Under kthr, kernel
threads, the b column indicates 2–3 threads per second are waiting. Under
memory, the fre column, the number of buffer frames available on the free is very
low.
The iostat command output investigation
The key values to check here are the % iowait and the % tm_act values.
Remember that the first output is the current status since startup.
The % iowait value
The % iowait is the percentage of time the CPU is idle while waiting on local I/O.
In this example, the %iowait has an average of 89.9 percent (add the column,
excluding the first line, and divide by nine). If the system’s % iowait is higher than
25 percent, it is advisable to investigate the problem and take corrective action.
The % tm_act value
The %tm_act is the percentage of time the disk is busy.
In this example, the % tm_act value had an average of 18.8 percent for hdisk0
and an average of 99.7 percent for hdisk1. If the percentage for the time a disk is
busy is high on a smaller system there will be noticeable performance
degradation on the system with less disks. In order to deliver good performance,
a system should be recording an average disk busy of less than 40 percent. This
is, however, not always possible with smaller systems with less disks.
Chapter 7. Performance scenario walkthroughs
255
7.2.3 Recommendation
The following are some recommendations to assist in improving disk I/O:
 Look for idle drives on the system; it may be possible to move some data from
busy drives to idle drives, which will give improved performance.
 Check the paging activity, as this may also be a factor. Spread the paging
over multiple drives if possible, thus sharing the paging space load across
multiple drives.
 If this is an occasional occurrence during month end, check which other
I/O-intensive processes are running and if they can be run earlier or later; this
way, the load is also spread across time.
7.3 Additional I/O scenarios
The following scenarios are examples of various command reports used as input
for tuning a system that has an I/O performance problem.
7.3.1 CPU and kernel thread I/O wait bottleneck scenario
The following scenario provides the following vmstat command report as input:
$ /usr/bin/vmstat 120 10
kthr
memory
page
----- ----------- -----------------------r b
avm
fre re pi po fr
sr cy
0 1 59903
542
0
0
0
0
0
0
0 2 59904
550
0
0
0
0
0
0
0 3 59950
538
0
0
0
0
0
0
0 2 59899
578
0
0
0
0
0
0
0 2 59882
589
0
0
0
0
0
0
0 3 59882
420
0
0
0
0
0
0
0 2 59954
420
0
0
0
0
0
0
0 2 59954
423
0
0
0
0
0
0
0 3 59954
420
0
0
0
0
0
0
0 2 59954
422
0
0
0
0
0
0
faults
-----------in
sy cs
451 912 478
521 1436 650
344 649 249
467 1829 500
600 1292 705
452 952 372
537 1979 573
618 1413 686
551 938 634
460 1376 496
cpu
----------us sy id wa
43 11 15 31
23 19 4 50
7 7 6 80
12 14 4 70
6 8 3 61
11 8 1 80
13 5 10 72
15 9 6 70
4 2 2 92
14 2 4 80
The vmstat report is taken over a period of 20 minutes using a 120 second
interval repeated 10 times. The first figures that are interesting in this report are
the cpu values (us/sy/id/wa). Notice that the CPU does have some idle (id) time,
but the largest value is the I/O wait (wa) time. Remember that the first
measurement can be excluded, because it is the average on the system since
startup.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The I/O wait time is increasing over the sample period from 50 percent and
peaking at 92 percent on the ninth measurement. The average I/O wait time over
the sample period is 72 percent, which indicates an I/O-related bottleneck.
The wa column specifies the percentage of time the CPU was idle with pending
local disk I/O. If there is at least one outstanding I/O to a local disk when wait is
running, the time is classified as waiting for I/O.
Generally, a wa value over 25 percent indicates that the disk subsystem may not
be balanced properly, or it may be the result of a disk-intensive workload.
Check the b value in the kernel thread column. The b column lists the average
number of kernel threads placed on the wait queue per second and should stay
near zero. These threads are waiting for resources or I/O.
Notice that the memory in relation to paging I/O can be ignored in this scenario,
as the paging parameters are all zero and the list of free memory pages (fre) is
still acceptable.
For more information on where the possible I/O bottleneck occurs, an iostat
command should be run on this system. This will provide information about how
the disk I/O is distributed between the physical volumes and where the possible
bottlenecks could be.
7.3.2 I/O distribution bottleneck scenario
This scenario returned the following lsps and iostat report:
# lsps -a
Page Space Physical Volume
hd6
hdisk0
# iostat 120 5
...
tty:
tin
tout
47.8
1394.6
Disks:
hdisk0
hdisk1
hdisk2
tty:
Disks:
hdisk0
hdisk1
% tm_act
97.0
0.8
0.2
tin
47.1
avg-cpu:
Kbps
124.4
21.5
0.3
tout
1046.3
% tm_act
98.5
0.6
Volume Group
rootvg
Kbps
186.1
23.8
% user
50.3
tps
59.3
16.8
0.1
avg-cpu:
Size
256MB
% sys
19.6
Kb_read
1924
492
8
% user
45.0
tps
56.4
18.5
%Used
13
% sys
40.0
Kb_read
9260
96
Active
yes
% idle
25.0
Auto
yes
Type
lv
% iowait
5.1
Kb_wrtn
12240
0
12
% idle
4.0
% iowait
11.0
Kb_wrtn
13008
332
Chapter 7. Performance scenario walkthroughs
257
hdisk2
tty:
0.3
tin
39.8
Disks:
hdisk0
hdisk1
hdisk2
tty:
Disks:
hdisk0
hdisk1
hdisk2
...
tout
1709.1
% tm_act
98.3
0.2
1.2
tin
32.9
Disks:
hdisk0
hdisk1
hdisk2
tty:
0.6
% tm_act
99.8
0.6
0.5
tin
33.6
Kbps
180.5
15.6
0.7
tps
7.5
2.9
0.2
% idle
10.0
% idle
22.0
% iowait
10.0
Kb_wrtn
20576
464
48
% sys
41.1
Kb_read
3132
80
12
% iowait
20.0
Kb_wrtn
12532
904
100
% sys
37.4
Kb_read
1364
672
24
% user
18.4
32
% sys
40.0
Kb_read
7144
312
36
% user
30.6
tps
22.6
16.8
0.3
avg-cpu:
4
% user
30.0
tps
55.2
26.6
0.5
avg-cpu:
Kbps
183.9
35.6
1.2
tout
875.5
% tm_act
98.9
0.2
0.3
avg-cpu:
Kbps
164.6
36.9
2.3
tout
1467.4
0.1
% idle
10.5
% iowait
30.0
Kb_wrtn
18560
808
32
The lsps command shows that the paging space is allocated on the physical
volume hdisk0.
The iostat report shown is collecting data over a 10-minute period in
120-second intervals. The first report is not shown and should be ignored for
real-time analysis, as it is the historical disk I/O report since startup. For details
on the iostat command report, see 4.2, “The iostat command” on page 118.
Notice the high I/O wait time (% iowait), which is increasing from 5.1 percent to
30 percent. Generally, if an I/O wait time exceeds 25 percent, there is a problem
related to disk I/O. There might be cases where I/O wait time is 0 percent and
there still is an I/O bottleneck. This can happen when the system is performing
extensive paging and the swap device is overloaded.
In the above iostat report, the activity on the hdisk0 is extremely high. The %
tm_act, indicating the active time of the disk in percent, is between 97 percent
and 99.8 percent, which is almost constantly active. This indicates that the I/O
bottleneck is bound to the disk hdisk0. Notice the Kb_wrtn value, indicating the
data written to the disk is fairly high compared to the amount of data read from
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
the disk. This leads to the conclusion that the I/O limits of the hdisk0 have been
reached. To improve the I/O performance, the other disks should be used more
actively, by moving hot file, file system, and logical volumes to the less active
disks. In general, a more insightful investigation may be required using other
tools such as filemon and lslv.
7.3.3 Logical volume fragmentation scenario
The lslv command is used for displaying the attributes of logical volumes, such
as the fragmentation of a logical volume on a physical volume.
Following is the lspv command output of a fragmented logical volume:
lslv -p hdisk0 lv00
hdisk0:lv00:N/A
0001
0002
0003
0011
0012
0013
0021
0022
0023
0031
0032
0004
0014
0024
0005
0015
0025
0006
0016
0026
0007
0017
0027
0008
0018
0028
0009
0019
0029
0010
0020
0030
1-10
11-20
21-30
31-32
0033
0043
0053
0063
0034
0044
0054
0064
0035
0045
0055
0036
0046
0056
0037
0047
0057
0038
0048
0058
0039
0049
0059
0040
0050
0060
0041
0051
0061
0042
0052
0062
33-42
43-52
53-62
63-64
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
65-74
75-84
85-94
95-95
USED
FREE
FREE
0068
USED
FREE
FREE
0069
USED
FREE
FREE
USED
FREE
FREE
USED
FREE
FREE
USED
FREE
FREE
USED
FREE
FREE
FREE
FREE
0065
FREE
FREE
0066
FREE
FREE
0067
96-105
106-115
116-125
126-127
FREE
USED
USED
USED
0070
USED
USED
USED
0071
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
USED
128-137
138-147
148-157
158-159
The logical volume consisting of 71 logical partitions (LPs) is fragmented over
four of the five possible intra-disk allocation sections. The sections’ outer edge
and outer middle are allocated from LPs 01–32 and 33–64, respectively, on
similar contiguously physical partitions. The LPs 65–69 are allocated in the inner
middle section and the last two LPs are allocated in the inner edge section.
This obvious fragmentation of logical volume lv00 can lead to a decrease in I/O
performance due to longer seek and disk head changes for a sequential
Chapter 7. Performance scenario walkthroughs
259
read/write operation in the last part of the logical volume. As there is free space
left on the physical volume, reorganizing lv00 is the action to take. Using the
reorgvg command on this logical volume will help improve the performance of
lv00.
For more information on the lslv command refer to 4.4, “LVM performance
analysis using the lslv command” on page 131.
7.3.4 Monitoring scenario using filemon
Consider a system with the following disks available:
# lspv
hdisk0
hdisk1
000bc6fdc3dc07a7
000bc6fdbff75ee2
rootvg
none
The following output shows a section of a filemon report made for monitoring the
logical volumes of a system.
The report was generated with the filemon command filemon -O lv -o
filemon.out:
...
Most Active Logical Volumes
------------------------------------------------------------------------util #rblk #wblk
KB/s volume
description
------------------------------------------------------------------------0.84 105792 149280
177.1
/dev/hd1
/home
0.32
0 16800
11.9
/dev/hd8
jfslog
0.03
0
4608
3.2
/dev/hd4
/
0.02
864 55296
5.9
/dev/hd2
/usr
0.02
192
4800
3.5
/dev/hd9var
/var
0.01
0
2976
2.1
/dev/hd8
jfslog
...
The output shows that the logical volume hd1, containing the /home file system,
has by far the highest utilization. As the second physical volume hdisk1 is not
used, as seen in the lspv report above, it would be possible to add this physical
volume to the rootvg and distribute hd1 to use both hdisk0 and hdisk1. This can
either be done by splitting the logical volume using an inter-disk policy of
maximum or by using the striping option.
7.3.5 Logical volume allocation scenario
The following scenario shows a series of status commands from a system with
an allocation problem on a dedicated database volume group:
# lsps -s
260
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Total Paging Space
100MB
# lsps -a
Page Space
hd6
Percent Used
37%
Physical Volume Volume Group
hdisk0
rootvg
Size
%Used Active Auto Type
100MB
38
yes
yes
lv
This shows that the paging space is defined in the hdisk0 of the rootvg.
The following volume group information is provided:
# lsvg
rootvg
datavg
# lspv
hdisk0
hdisk1
hdisk2
hdisk3
000038744c632197
00002199abf65a1a
00000228b9c5d7da
00002199b40b728c
rootvg
datavg
datavg
datavg
This shows that two volume groups are defined, rootvg on hdisk1 and datavg on
hdisk1, hdisk2, and hdisk3.
hdisk0 contains the following logical volumes:
# lspv -l hdisk0
hdisk0:
LV NAME
hd5
hd3
hd2
hd8
hd4
hd9var
hd6
hd1
lv00
LPs
2
6
117
1
2
1
128
3
10
PPs
2
6
117
1
2
1
128
3
10
DISTRIBUTION
02..00..00..00..00
02..00..04..00..00
00..47..42..28..00
00..00..01..00..00
00..00..02..00..00
00..00..01..00..00
29..50..49..00..00
00..00..01..02..00
00..00..00..10..00
MOUNT POINT
N/A
/tmp
/usr
N/A
/
/var
N/A
/home
/database
The rootvg on hdisk0 contains all the default logical volume and file systems and
an additional lv00 containing the /database file system.
The other disk contains:
# lspv -l hdisk1
hdisk1:
LV NAME
loglv00
lv01
LPs
1
10
PPs
1
10
DISTRIBUTION
01..00..00..00..00
00..00..00..00..10
MOUNT POINT
N/A
/db01
Chapter 7. Performance scenario walkthroughs
261
lv02
lv03
10
10
10
10
00..00..00..00..10
10..00..00..00..00
/db02
/db03
# lspv -l hdisk2
hdisk2:
LV NAME
LPs
PPs
DISTRIBUTION
MOUNT POINT
# lspv -l hdisk3
hdisk3:
LV NAME
LPs
PPs
DISTRIBUTION
MOUNT POINT
The logical volumes of the datavg volume group are all allocated on the same
physical volume hdisk1, including the jfs log loglv00. This shows that the physical
volumes hdisk2 and hdisk3 are unused.
The details of the datavg LVs are as follows:
# lslv lv01
LOGICAL VOLUME:
lv01
LV IDENTIFIER:
0000881962b29b51.1
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
1
LPs:
1
STALE PPs:
0
INTER-POLICY:
minimum
INTRA-POLICY:
middle
MOUNT POINT:
/db01
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
# lslv lv02
LOGICAL VOLUME:
lv02
LV IDENTIFIER:
0000881962b29b51.3
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
1
LPs:
1
STALE PPs:
0
INTER-POLICY:
minimum
INTRA-POLICY:
middle
MOUNT POINT:
/db02
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
# lslv lv03
LOGICAL VOLUME:
262
lv03
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
datavg
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
/db01
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
datavg
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
/db02
VOLUME GROUP:
datavg
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
LV IDENTIFIER:
0000881962b29b51.4
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
1
LPs:
1
STALE PPs:
0
INTER-POLICY:
minimum
INTRA-POLICY:
middle
MOUNT POINT:
/db03
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
/db03
When generating the logical volumes lv01, lv02, and lv03, the system
administrator should have dedicated each of the LVs on a corresponding
physical volume. Alternatively, the inter-disk allocation policy could have been
set to maximum and limit the upper bound to 1.
In this way, the lv01 and the corresponding /db01 would reside on hdisk1, lv02
and /db02 on hdisk2, and lv03 and /db03 on hdisk3.
A modification to this can be done using the migratepv command.
To distribute the load of the default jfslog on the hdisk1 to the other physical
volume in the datavg, an additional jfslog for each file system could be created.
Defining a dedicated JFS log for both /db02 and /db03 would improve the
performance. In this way, the different file systems residing on their individual
disks would not utilize the hdisk1 for the JFS logging, but rather their own
physical volumes.
7.4 Paging performance scenario
In this section, paging performance will be investigated. The symptoms of high
memory utilization will be described and possible corrective action will be
explained.
7.4.1 Data collection
In the following section, the system outputs are gathered by the svmon and
vmstat commands.
Chapter 7. Performance scenario walkthroughs
263
Below is the output of an idle system using the vmstat command:
# vmstat 1 5
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy
in
sy cs us sy id wa
0 0 11106 107916
0
0
0
0
0
0 125 570 66 1 4 88 7
0 0 11106 107915
0
0
0
0
0
0 112 397 42 0 0 98 2
0 0 11106 107915
0
0
0
0
0
0 107 192 23 0 0 99 0
0 0 11106 107915
0
0
0
0
0
0 110 280 28 0 0 99 0
0 0 11106 107915
0
0
0
0
0
0 109 174 27 1 0 99 0
Below is the output of a system with high memory utilization using the vmstat
command:
# vmstat 1 15
kthr
memory
page
faults
cpu
----- ----------- ------------------------ ------------ ----------r b
avm
fre re pi po fr
sr cy in
sy cs us sy id wa
0 0 204340
72
0
0
5
8
25
0 108
249 29 0 1 98 1
3 4 204649
124
0 31 422 449 912
0 347 4796 350 5 95 0 0
1 3 204988
112
0 56 183 464 1379
0 339 14144 382 4 96 0 0
9 0 205292
122
0 24 251 369 988
0 352
598 403 4 94 0 2
3 1 205732
119
0
0 409 520 771
0 313
780 293 1 99 0 0
3 1 206078
123
0
0 445 496 602
0 336
706 298 2 98 0 0
3 1 206460
120
0
0 343 504 1210
0 305
719 271 1 99 0 0
2 1 206897
119
0
0 320 512 981
0 311
660 288 0 99 0 0
3 1 207186
126
0
1 369 504 929
0 331
718 292 1 99 0 0
3 1 207491
120
0
1 428 504 844
0 319
763 262 1 99 0 0
4 0 207964
119
0
0 275 520 791
0 296
632 283 0 99 0 0
4 0 208354
119
0
2 373 513 816
0 328
664 297 1 99 0 0
4 0 208715
87
0
4 383 464 753
0 330 1480 261 4 96 0 0
3 1 209006
4
0 12 282 504 630
0 350 1 385 286 2 98 0 0
3 2 209307
10
0
0 316 488 685
0 320
635 287 1 92 0 7
The following command outputs will be used for reference purposes or as
comparisons. Each of these outputs were taken during the vmstat output above.
The output of the ps command appears as follows:
# ps gv | head -n 1; ps gv | egrep -v "RSS" | sort +6b -7 -n -r
PID
TTY STAT TIME PGIN SIZE
RSS
LIM TSIZ
TRS %CPU %MEM COMMAND
12478 pts/4 A
2:05
91 742240 362552 32768
2
4 50.8 69.0 ./tmp/me
1032
- A
0:56
0
64 6144
xx
0 6088 0.0 1.0 kproc
774
- A
0:01
0
16 6104
xx
0 6088 0.0 1.0 kproc
7484
- A
0:00
6
16 6104 32768
0 6088 0.0 1.0 kproc
10580
- A
0:00
1
16 6104 32768
0 6088 0.0 1.0 kproc
0
- A
0:20
7
12 6100
xx
0 6088 0.0 1.0 swapper
516
- A
3920:23
0
8 6096
xx
0 6088 98.7 1.0 kproc
2076
- A
0:00
0
16 6096
xx
0 6088 0.0 1.0 kproc
264
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
3622
7740
4994
15434
4564
15808
5686
11402
2622
16114
16236
11982
13934
14462
16412
1
pts/5
pts/5
pts/0
pts/2
pts/0
pts/1
pts/0
pts/5
pts/4
pts/2
pts/3
pts/5
- A
pts/0
pts/0
pts/3
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
0:00
0
16 6096
xx
0 6088
0:00
0
16 6096 32768
0 6088
0:00
24
440
708 32768
198
220
0:00
0
368
396 32768
198
220
0:00
0
308
392 32768
198
220
0:00 292
304
388 32768
198
220
0:00 320
280
348 32768
198
220
0:00 225
296
336 32768
198
220
0:39 469 3208
324
xx 2170
112
0:00
0
240
324 32768
52
60
0:00
12
360
252 32768
198
220
0:00 160
304
240 32768
198
220
0:00 234
304
236 32768
198
220
0:00 231
308
232 32768
198
220
0:00 129
304
232 32768
198
220
0:07 642
760
224 32768
25
36 0.0
A
0:02 394
728
212 32768
337
80
A
0:00 567
644
208 32768
327
64
A
5:22 340 1152
204
xx
40
0
A
0:00
71
88
196 32768
43
68
A
0:00
1
148
196 32768
16
24
A
1:53 30625
228
192 32768
10
12
6708
6212
3124
17316
17556
12886
/u/
16960 pts/0 A
13104 pts/1 A
13466 pts/5 A
4774
- A
13796 pts/5 A
14856 pts/5 A
5440
- A
9292
- A
1920
- A
/usr/sbin
14198
- A
2516
- A
8000
- A
8780
- A
11614
- A
12788
- A
14710
- A
15298
- A
2874
- A
3402
0 A
3900
- A
4134
- A
5176
- A
5938
- A
6450
- A
6966
- A
0:00
40
0:00
63
0:00
0
0:00 217
0:00
4
0:01
0
0:00 228
0:00 183
0:50 16272
0:00 274
0:00
0
0:00
51
0:00
19
0:00
9
0:00 102
0:00 350
0:00
0
0:00
29
0:00
5
0:00 442
0:00
26
0:00
44
0:00
37
0:00
99
0:00
52
132
132
104
284
80
72
292
128
96
740
656
656
120
180
740
740
740
288
180
460
400
456
280
304
428
184 32768
156 32768
136 32768
124 32768
76 32768
64 32768
60 32768
60 32768
36
xx
20 32768
16 32768
16 32768
16 32768
16 32768
16 32768
16 32768
16 32768
12
xx
12
xx
12
xx
12
xx
12 32768
12 32768
12 32768
12 32768
15
15
2
30
18
18
25
53
20
20
4
28
24
24
20
20
2
313
313
313
3
18
313
313
313
100
34
56
100
31
36
25
190
4
4
4
0
0
4
4
4
0
0
0
0
0
0
0
0
0.0 1.0 kproc
0.0 1.0 kproc
0.0 0.0 ksh /usr/
0.0 0.0 ksh /usr/
0.0 0.0 -ksh
0.0 0.0 ksh
0.0 0.0 -ksh
0.0 0.0 -ksh
0.0 0.0 /usr/lpp/
0.0 0.0 ps gv
0.0 0.0 ksh /usr/
0.0 0.0 -ksh
0.0 0.0 -ksh
0.0 0.0 -ksh
0.0 0.0 -ksh
0.0 /etc/init
0.0 0.0 /usr/sbin
0.0 0.0 sendmail:
0.1 0.0 dtgreet
0.0 0.0 svmon -i
0.0 0.0 egrep -v
9.8 0.0 cp -r
0.0
0.0
0.0
0.0
0.0
1.1
0.0
0.0
4 0.0
0.0 vmstat 1
0.0 vmstat 1
0.0 /usr/bin/
0.0 /usr/sbin
0.0 dd conv=s
0.0 dd conv=s
0.0 /usr/sbin
0.0 /usr/sbin
0.0
0.0 0.0 telnetd 0.0 0.0 telnetd 0.0 0.0 telnetd 0.0 0.0 /usr/sbin
0.0 0.0 /usr/lpp/
0.0 0.0 telnetd 0.0 0.0 telnetd 0.0 0.0 telnetd 0.0 0.0 /usr/dt/b
0.0 0.0 slattach
0.0 0.0 /usr/lib/
0.0 0.0 dtlogin <
0.0 0.0 /usr/sbin
0.0 0.0 /usr/sbin
0.0 0.0 /usr/sbin
0.0 0.0 /usr/sbin
Chapter 7. Performance scenario walkthroughs
265
7224
8260
8522
9040
9554
9808
10838
11094
lft0
-
A
A
A
A
A
A
A
A
0:00
0:00
0:00
0:00
0:00
0:00
0:00
0:00
56
1
13
3
5
12
17
13
500
96
292
36
220
312
372
256
12
12
12
12
12
12
12
12
32768
32768
32768
32768
32768
32768
32768
32768
191
2
21
5
12
64
40
22
0
0
0
0
0
0
0
0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
The output of the svmon command appears as follows:
# svmon -i 5 5
size
inuse
memory
131063
pg space
131072
free
130936
106986
pin
in use
work
6955
104809
pers
0
26127
clnt
0
0
memory
pg space
size
131063
131072
inuse
130942
108647
free
121
pin
in use
work
6951
105067
pers
0
25875
clnt
0
0
memory
pg space
size
131063
131072
inuse
130951
110432
free
113
work
pin
in use
266
pers
pin
virtual
127
6946
204676
pin
6942
virtual
206567
pin
6942
virtual
208406
pin
6942
virtual
206567
pin
virtual
clnt
6955
104809
0
26127
0
0
memory
pg space
size
131063
131072
inuse
130942
108647
free
121
pin
in use
work
6951
105067
pers
0
25875
clnt
0
0
size
inuse
free
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
/usr/sbin
/usr/sbin
/usr/sbin
/usr/sbin
/usr/sbin
/usr/bin/
/usr/sbin
/usr/IMNS
memory
pg space
131063
131072
130951
110432
113
pin
in use
work
6951
105127
pers
0
25824
clnt
0
0
6942
208406
The output showing the top ten memory-using processes using the svmon
command appears as follows:
# svmon -Pu -t 10
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
12478 memory
92498
1259
95911
189707
N
N
Vsid
7a80
d18a
4358
0
Esid
5
3
4
0
65475..65535
8811
c93
e6ec
5d79
e28c
735e
767c
65314..65535
3e76
634c
Inuse
52911
31670
4963
1522
Pin
0
0
0
1258
shared library text
shmat/mmap
shmat/mmap
shmat/mmap
shmat/mmap
shmat/mmap
process private
274
244
240
234
232
200
4
0
0
0
0
0
0
1
24
12
16
22
24
55
3
393
256
256
256
256
255
5
f work shared library data
1 pers code,/dev/hd3:21
3
1
0
0
4
-
5
-
d
8
7
6
9
a
2
Type
work
work
work
work
Description
shmat/mmap
shmat/mmap
shmat/mmap
kernel seg
work
work
work
work
work
work
work
Pgsp Virtual Addr Range
222 53058
0..65285
33881 65535
0..65535
60572 65535
0..65535
1076 3897
0..32767 :
0..65535
0..65288
0..65287
0..65286
0..65289
0..65034
0..709
0..2
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
13796 dd
2829
1260
1100
4303
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
65475..65535
dc53
8811
edae
- pers /dev/hd3:45
d work shared library text
2 work process private
1011
274
8
0
0
1
24
0
393
8
65310..65535
83b0
dbb3
1 pers code,/dev/hd2:4164
f work shared library data
6
5
0
0
0
2
0..1010
0..65535
0..20 :
0..5
0..797
Chapter 7. Performance scenario walkthroughs
267
949a
ac7d
ac5d
3 work shmat/mmap
4 work shmat/mmap
5 work shmat/mmap
1
1
1
1
0
0
0
0
0
1
1
1
0..0
0..0
0..0
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
14856 dd
2826
1260
1100
4301
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
65475..65535
65475..65535
dc53
8811
83b0
6ce5
d
1
2
pers
work
pers
work
/dev/hd3:45
shared library text
code,/dev/hd2:4164
process private
1011
274
6
6
0
0
0
1
24
0
393
6
65310..65535
5cc3
949a
ac7d
ac5d
f
3
4
5
work
work
work
work
shared library data
shmat/mmap
shmat/mmap
shmat/mmap
4
1
1
1
0
1
0
0
0
0
0
0
2
1
1
1
0..1010
0..65535
0..5
0..19 :
0..797
0..0
0..0
0..0
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
4994 ksh
1975
1259
1100
4400
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
65475..65535
8811
7b7c
d work shared library text
2 work process private
274
98
0
1
24
0
65310..65535
e03c
c72a
2865
4b89
1 pers code,/dev/hd2:4204
f work shared library data
pers /dev/hd2:32343
- pers /dev/hd2:10340
55
24
0
0
0
2
0
0
0
-
393
96
0..65535
0..115 :
0..58
14
0..797
0..1
0..10
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
15434 ksh
1897
1259
1100
4328
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
65475..65535
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
8811
e03c
92c3
d work shared library text
1 pers code,/dev/hd2:4204
2 work process private
65310..65535
30f7
2865
536a
c91
f
-
work
pers
pers
pers
shared library data
/dev/hd2:32343
/dev/hd2:4522
/dev/hd3:29
274
55
29
0
0
1
24
0
393
28
15
2
0
0
0
0
0
0
0
-
10
-
0..65535
0..58
0..94 :
0..797
0..1
0..7
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
16728 -ksh
1897
1259
1103
4324
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
65475..65535
8811
e03c
ef7a
d work shared library text
1 pers code,/dev/hd2:4204
2 work process private
65310..65535
8717
2865
a2f4
f96d
f
-
work
pers
pers
pers
shared library data
/dev/hd2:32343
/dev/hd4:792
/dev/hd3:40
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
274
55
24
0
0
1
24
2
393
23
18
2
1
1
0
0
0
0
1
-
11
-
0..65535
0..58
0..83 :
0..382
0..1
0..1
0..0
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
15808 ksh
1896
1259
1166
4366
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
65475..65535
8811
d work shared library text
e03c
1 pers code,/dev/hd2:4204
cec9
2 work process private
65310..65535
1752
2865
e35c
f work shared library data
- pers /dev/hd2:32343
- pers /dev/hd1:19
274
55
25
17
2
1
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
0
0
1
24
54
0
0
0
12
-
393
0..65535
0..58
62
0..91 :
14
-
0..797
0..1
0..0
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
2622 X
1888
1268
1889
5132
N
N
Chapter 7. Performance scenario walkthroughs
269
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
8811
8971
d work shared library text
2 work process private
65309..65535
9172
fa9f
3987
b176
e97d
d97b
3186
180
4168
1963
90b2
9092
1 pers
- work
3 work
f work
- pers
- pers
work
- pers
- pers
- pers
- work
- pers
Inuse
1522
274
52
0
8
24
712
28
9
2
1
0
0
0
0
2
0
0
0
32
2
39
-
code,/dev/hd2:18475
shmat/mmap
shared library data
/dev/hd2:20486
/dev/hd3:25
0
/dev/hd2:20485
/dev/hd9var:2079
/dev/hd9var:2078
/dev/hd4:2
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
0
0
0
0
0
0
2
0
0
0
0
0
2
-
393
763
0..65535
0..825 :
0..706
32
0..32783
4
0..32767
39
0..310
0..7
2
0..32768
0..0
0..0
0..0
2
0..32768
0..0
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
11402 -ksh
1882
1259
1166
4364
N
N
Vsid
0
Esid Type Description
0 work kernel seg
Inuse
1522
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
65475..65535
8811
e03c
6b0d
d work shared library text
1 pers code,/dev/hd2:4204
2 work process private
274
55
18
0
0
1
24
52
393
59
65310..65535
4328
2865
3326
f work shared library data
- pers /dev/hd2:32343
- pers /dev/hd4:605
11
2
0
0
0
0
14
-
15
-
0..65535
0..58
0..83 :
0..382
0..1
0..1
------------------------------------------------------------------------------Pid Command
Inuse
Pin
Pgsp Virtual
64-bit
Mthrd
5686 -ksh
1872
1259
1106
4304
N
N
Vsid
0
Esid Type Description
0 work kernel seg
65475..65535
8811
e03c
72ee
270
d work shared library text
1 pers code,/dev/hd2:4204
2 work process private
Inuse
1522
274
55
12
Pin Pgsp Virtual Addr Range
1258 1076 3897
0..32767 :
0
0
1
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
24
5
393
12
0..65535
0..58
0..82 :
65310..65535
6aed
2865
a2f4
f work shared library data
- pers /dev/hd2:32343
- pers /dev/hd4:792
6
2
1
0
0
0
1
-
2
-
0..382
0..1
0..1
A snapshot of the paging space at various intervals using the command:
# lsps -a
Page Space
hd6
# lsps -a
Page Space
hd6
# lsps -a
Page Space
hd6
Physical Volume
hdisk0
Volume Group
rootvg
Size
512MB
%Used
95
Active
yes
Auto
yes
Type
lv
Physical Volume
hdisk0
Volume Group
rootvg
Size
512MB
%Used
97
Active
yes
Auto
yes
Type
lv
Physical Volume
hdisk0
Volume Group
rootvg
Size
512MB
%Used
9
Active
yes
Auto
yes
Type
lv
The output of the vmtune command:
# vmtune
vmtune: current values:
-p
-P
-r
-R
minperm maxperm minpgahead maxpgahead
26007
104028
2
8
-f
minfree
120
-F
maxfree
128
-N
-W
pd_npages maxrandwrt
524288
0
-M
-w
-k
-c
-b
-B
-u
-l
maxpin npswarn npskill numclust numfsbufs hd_pbuf_cnt lvm_bufcnt lrubucket
defps
104851
4096
1024
1
93
80
9
131072
-s
sync_release_ilock
0
-n
nokillroot
0
-S
v_pinshm
0
number of valid memory pages = 131063
maximum pinable=80.0% of real memory
number of file memory pages = 13516
-d
1
-h
strict_maxperm
0
maxperm=79.4% of real memory
minperm=19.8% of real memory
numperm=10.3% of real memory
Display the number of processors using the lsdev command:
# lsdev -Ccprocessor
proc0 Available 00-00 Processor
This is a single processor system.
7.4.2 Data analysis
From the output in the previous section, an investigation can be done on the
various components within the system to determine the areas that are causing
Chapter 7. Performance scenario walkthroughs
271
performance problems. For this investigation, the output will mostly be from the
vmstat command output. The other output is for information and confirmation.
The kthr (kernel thread) column
The kthr column provides information about the average number of threads on
various queues.
Both the r and b counts are low, indicating that the system is executing the
runable threads in the kernel sufficiently. The contention for CPU resources is
low.
The memory column
The memory column displays information about the use of real and virtual
memory. A page is 4096 bytes in size.
In the avm column it can be seen that the average number of pages allocated
increased. The system will keep allocating pages until all paging space available
is used (check with the lsps -a command). When all the paging space has been
utilized or reaches 100 percent, the system will start killing processes to make
paging space available for use.
The fre column shows the average number of free memory pages. The
MINFREE value for this system is 120, as shown with the vmtune command. In
the example, the free memory stayed around the MINFREE value until it dropped
to below 100 and almost to 0. This is one of the indications that the system was
thrashing.
The page column
The page column displays information about page faults and paging activity.
These averages are given per second. Paging space is the part of virtual
memory that resides on disk. It is used as an overflow when memory is
overcommitted. Paging consists of paging logical volumes dedicated to the
storage of working set pages that have been stolen from real memory. When a
stolen page is referenced by the process, a page fault occurs and the page must
be read into memory from paging space. Whenever a page of working storage is
stolen, it is written to paging space. If not referenced again, it remains on the
paging device until the process terminates or disclaims the space. Subsequent
references to addresses contained within the faulted-out pages result in page
faults, and the pages are paged in individually by the system. When a process
terminates normally, any paging space allocated to that process is freed.
The re column, which is the number of reclaimed pages, remained at 0
throughout.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
The pi column varied from 0 to the highest level of 56 pages paged in from
paging space. Although a pi level of no more than 5 is considered acceptable, a
level higher than 5 is not necessarily an indication of a performance problem,
due to the fact that for every page paged in, there must have been a page that
was paged out.
The po column, which reflects the number of pages paged out, was between 183
and 445 per second. With a high rate of paging, the system may see some
performance degradation, as the paging space is kept on the hard disk and is
accessed slower than RAM.
The fr column is the number of pages freed in a second.
The sr column is the number of pages scanned by the page placement algorithm.
If the ratio between fr:sr is high, this can indicate a memory constraint, for
example, if the ratio is 1:3, it will mean that for every page freed, three will need
to be checked. In the example, the ratio is close to 1:2.
The faults column
The information under the faults heading displays the trap and interrupt rate
averages per second.
The in column is the number of device interrupts per second and is always
greater than 100.
The sy column is the number of system calls and it is extremely difficult to say
what this figure should be.
The cs column is the number of context switches.
The cpu column
The information under the cpu heading provides a breakdown of CPU usage.
The us column indicates the amount of time spent in user mode. In the example,
this is never above 5 percent.
The sy column indicates the amount of time spent in system mode. In this
example, it is never below 92 percent.
The id column indicates the amount of idle time. In this example, the cpu is never
idle.
The wa column indicates the amount of idle time with pending local disk I/O. In
the example, it is never higher than seven percent.
Chapter 7. Performance scenario walkthroughs
273
Note: In a single processor system, if us + sy is greater than 90 percent, the
system can be considered CPU bound.
7.4.3 Recommendation
From the data, the following are some recommendations that can be
implemented to ease the situation:
 If it is possible, an additional CPU might be added to try and get the CPU
utilization below 80 percent.
 Add an additional paging space on another internal disk. The reason for
adding this paging area to an internal disk is for speed and availability. It is
advisable to always spread the paging space across multiple disks, as this
will improve paging performance.
 If this is a situation that occurs only at certain times, it may be possible to
reschedule large jobs and spread them out, so as not to conflict with one
another.
274
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
8
Chapter 8.
Scenario assessment quiz
In this chapter you will be provided with two scenarios to examine and questions
to answer based on those scenarios.
© Copyright IBM Corp. 2002. All rights reserved.
275
8.1 Scenario one
Robutz, Inc. is a small startup robot toy manufacturing company. They decided to
purchase an RS/6000 F50 to keep track of their suppliers, inventory, production
schedules as well as marketing support. The system they purchased consists of
the following components:
 F50 running AIX Version 4.3.2
 Single 166 MHz PowerPC 604e
 RAM 128 MB
 3–4.5 GB SCSI Disk Drives
 1–8 mm Tape Drive
 Integrated 10 Mbps Ethernet will be used to connect to their network.
 They anticipate seven users to be using the system, connecting with their
PCs over the network.
 They will be using an off-the-shelf program with Sybase as their database.
 They will have two network printers.
 They have decided to create three Volume Groups (each on separate disk):
rootvg, sybasevg, and dumpvg.
Scenario questions:
1. Using a customer’s vmtune settings, which of the following parameters should
be changed to help eliminate paging?
# vmtune
vmtune: current values:
-p
-P
-r
-R
minperm maxperm minpgahead maxpgahead
maxrandwrt
6344
25376
2
8
-f
minfree
-F
maxfree
-N
pd_npages
120
128
524288
-W
0
-M
-w
-k
-c
-b
-B
-u
-l
maxpin npswarn npskill numclust numfsbufs hd_pbuf_cnt lvm_bufcnt lrubucket
defps
26196
1024
256
1
93
64
9
131072
0
-s
-n
sync_release_ilock nokilluid
0
0
-S
-h
v_pinshm strict_maxperm
0
0
number of valid memory pages = 32744
maximum pinable=80.0% of real memory
276
maxperm=77.5% of real memory
minperm=19.4% of real memory
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
number of file memory pages = 24067
A.
maxpin
B.
maxfree
numperm=73.5% of real memory
C. maxperm
D.
maxpgahead
2. Using the vmtune output, as shown in the exhibit, which of the following is the
most probable cause for the high paging space allocation?
# vmtune
vmtune: current values:
-p
-P
-r
-R
minperm maxperm minpgahead maxpgahead
maxrandwrt
6344
25376
2
8
-f
minfree
-F
maxfree
-N
pd_npages
120
128
524288
-W
0
-M
-w
-k
-c
-b
-B
-u
-l
maxpin npswarn npskill numclust numfsbufs hd_pbuf_cnt lvm_bufcnt lrubucket
defps
26196
1024
256
1
93
64
9
131072
0
-s
-n
sync_release_ilock nokilluid
0
0
-S
-h
v_pinshm strict_maxperm
0
0
number of valid memory pages = 32744
maximum pinable=80.0% of real memory
number of file memory pages = 24067
A.
defps is 0.
B.
minpgahead is 2.
maxperm=77.5% of real memory
minperm=19.4% of real memory
numperm=73.5% of real memory
C. maxpgahead is 8.
D.
maxfree is 128.
8.1.1 Answers
The following are the preferred answers to the questions provided in this section.
1. C
2. A
Chapter 8. Scenario assessment quiz
277
8.2 Scenario two
MooCow Inc. has a single processor F50 with 512 MB of memory and four 4.5
GB SCSI drives. They have a flat IP network using the built-in 10 Mbps Ethernet
adapter and are running AIX Version 4.3.3 with all the latest PTFs. The system
administrator reboots the system every Sunday after their full-weekly backup.
Throughout the week, the users notice degrading performance with the
application A response time.
1. Which of the following tools should be used to begin gathering historical
performance data on the system for a performance analysis?
A.
sar
B.
iostat
C. netstat
D. vmstat
2. MooCow Inc. has added a CPU, increased physical memory, and installed
another two SCSI drives in order to support application B. Since application B
has been installed, users are complaining about application response times
during peak business hours.
Use the information provided in Figure 8-1, Figure 8-2 on page 279,
Figure 8-3 on page 279, and Figure 8-4 on page 280 to help you with your
answer.
Figure 8-1 The ps command output
278
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure 8-2 The vmstat command output
Figure 8-3 The iostat command output
Chapter 8. Scenario assessment quiz
279
Figure 8-4 The netstat command output
280
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Using information provided in the exhibits, which of the following conclusions
is most appropriate to draw about the problem on the system?
A.
The system is CPU bound.
B.
The system is I/O bound.
C. The system is memory bound.
D.
The system is network bound.
3. Based on the statistics, which of the following reports helped to determine the
problem?
A.
The stime from the ps report
B.
The % user and % sys metrics from the iostat report
C. The statistics from the b column in the vmstat report
D.
The number of requests for mbufs denied from the netstat report
4. Which of the following procedures should be performed to remedy the
situation?
A.
Stripe the logical volumes.
B.
Increase the tcp_sendspace to 65536.
C. Use vmtune to change the file system cache.
D.
Move the /usr/app/exp_report process to off-peak hours.
5. The actions taken so far have only increased performance slightly. The
service level agreement is still not being achieved. Which of the following
procedures should be performed?
A.
Install a PCI SCSI-RAID adapter.
B.
Install another 512 MB of memory.
C. Upgrade to a four-way processor.
D.
Upgrade to a 10/100 Ethernet adapter.
6. Which of the following should be implemented to balance available
CPU/memory resources between applications?
A.
Loadleveler
B.
Nice/renice
C. Resource Manager
D.
Workload Manager
Chapter 8. Scenario assessment quiz
281
7. MooCow Inc. is still experiencing performance problems. Using the output
shown in Figure 8-5, which of the following conclusions is most appropriate to
draw?
Figure 8-5 The vmstat and iostat command outputs
282
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
A.
The system is CPU bound.
B.
The system is I/O bound.
C. The system is memory bound.
D.
The system is network bound.
8. Given the details of the exhibit, which of the following procedures should be
performed to fix the bottleneck?
A.
Add CPU(s).
B.
Add 512 MB of memory.
C. Stripe the logical volumes.
D.
Implement a switched Ethernet.
9. The backups for a system are being taken over the network to a TSM Server.
Unfortunately, they are taking too long and the service level agreement is not
being met with the customer. Based upon the current configuration and
details shown in the exhibit, which of the following tuning procedures should
be performed to improve the file system’s backup performance?
A.
Increase the maxfree value using vmtune.
B.
Increase the mult value using schedtune.
C. Increase the queue length on the disk drives using chdev.
D.
Increase the tcp_sendspace and tcp_recvspace on your system and the
TSM Server.
10.The backups are still not meeting the service level agreement. It has been
suggested that you to re-examine the I/O performance.
# lsps -s
Total Paging Space
100MB
# lsps -a
Page Space
Type
hd6
lv
Percent Used
37%
Physical Volume
Volume Group
hdisk0
rootvg
Size
%Used
Active
Auto
100MB
38
yes
yes
# lsvg
rootvg
datavg
# lspv
hdisk0
000038744c632197
rootvg
Chapter 8. Scenario assessment quiz
283
hdisk1
hdisk2
hdisk3
00002199abf65a1a
00000228b9c5d7da
00002199b40b728c
# lspv -l hdisk0
hdisk0:
LV NAME
hd5
hd3
hd2
hd8
hd4
hd9var
hd6
hd1
lv00
LPs
2
6
117
1
2
1
128
3
10
PPs
2
6
117
1
2
1
128
3
10
DISTRIBUTION
02..00..00..00..00
02..00..04..00..00
00..47..42..28..00
00..00..01..00..00
00..00..02..00..00
00..00..01..00..00
29..50..49..00..00
00..00..01..02..00
00..00..00..10..00
MOUNT POINT
N/A
/tmp
/usr
N/A
/
/var
N/A
/home
/database
# lspv -l hdisk1
hdisk1:
LV NAME
loglv00
lv01
lv02
lv03
LPs
1
10
10
10
PPs
1
10
10
10
DISTRIBUTION
01..00..00..00..00
00..00..00..00..10
00..00..00..00..10
10..00..00..00..00
MOUNT POINT
N/A
/db01
/db02
/db03
# lspv -l hdisk2
hdisk2:
LV NAME
LPs
PPs
DISTRIBUTION
MOUNT POINT
# lspv -l hdisk3
hdisk3:
LV NAME
LPs
PPs
DISTRIBUTION
MOUNT POINT
# lslv lv01
LOGICAL VOLUME:
LV IDENTIFIER:
VG STATE:
TYPE:
MAX LPs:
COPIES:
LPs:
STALE PPs:
INTER-POLICY:
INTRA-POLICY:
284
datavg
datavg
datavg
lv01
0000881962b29b51.1
active/complete
jfs
512
1
1
0
minimum
middle
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
datavg
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
LOGICAL VOLUME:
lv01
MOUNT POINT:
/db01
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
# lslv lv02
LOGICAL VOLUME:
lv02
LV IDENTIFIER:
0000881962b29b51.3
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
1
LPs:
1
STALE PPs:
0
INTER-POLICY:
minimum
INTRA-POLICY:
middle
MOUNT POINT:
/db02
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
VOLUME GROUP:
LABEL:
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
# lslv lv03
LOGICAL VOLUME:
lv03
LV IDENTIFIER:
0000881962b29b51.4
VG STATE:
active/complete
TYPE:
jfs
MAX LPs:
512
COPIES:
1
LPs:
1
STALE PPs:
0
INTER-POLICY:
minimum
INTRA-POLICY:
middle
MOUNT POINT:
/db03
MIRROR WRITE CONSISTENCY: on
EACH LP COPY ON A SEPARATE PV ?: yes
VOLUME GROUP:
PERMISSION:
LV STATE:
WRITE VERIFY:
PP SIZE:
SCHED POLICY:
PPs:
BB POLICY:
RELOCATABLE:
UPPER BOUND:
LABEL:
datavg
/db01
datavg
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
/db02
datavg
read/write
opened/syncd
off
8 megabyte(s)
parallel
1
relocatable
yes
32
/db03
Chapter 8. Scenario assessment quiz
285
Using information provided in the exhibits, which of the following procedures
should be performed to improve the I/O performance?
A.
Change the stripe size to 32 KB.
B.
Adjust the value of maxrndwrt.
C. Upgrade your disk subsystem to RAID 5.
D.
Move each file system to separate disks.
11.The actions taken so far have helped, but more actions are necessary. Which
of the following procedures should be performed to accelerate performance of
the I/O?
A.
Disable the write consistency check.
B.
Add a JFS log for each file system.
C. Increase the maxpin parameter with vmtune.
D.
Increase the syncd frequency from 60 to 10.
8.2.1 Answers
The following are the preferred answers to the questions provided in this section.
1. A
2. A
3. B
4. D
5. C
6. D
7. D
8. D
9. D
10.D
11.B
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
A
Appendix A.
The error log
The following topics are discussed in this appendix:
 A general discussion about the error logging subsystem
 How to manage error logs
 How to read error logs
The error log is the first place where an administrator will search for the cause of
improper system performance.
© Copyright IBM Corp. 2002. All rights reserved.
287
Overview
The error-logging process begins when an operating system module detects an
error. The error-detecting segment of code then sends error information to either
the errsave and errlast kernel services or the errlog application subroutine where
the information is, in turn, written to the /dev/error special file. This process then
adds a timestamp to the collected data. The errdemon daemon constantly
checks the /dev/error file for new entries, and when new data is written, the
daemon conducts a series of operations.
Before an entry is written to the error log, the errdemon daemon compares the
label sent by the kernel or application code to the contents of the error record
template repository. If the label matches an item in the repository, the daemon
collects additional data from other parts of the system.
The system administrator can look at the error log to determine what caused a
failure, or to periodically check the health of the system when it is running.
The software components that allow the AIX kernel and commands to log errors
to the error log are contained in the fileset bos.rte.serv_aid. This fileset is
automatically installed as part of the AIX installation process.
The commands that allow you to view and manipulate the error log, such as the
errpt and errclear commands, are contained in the fileset called
bos.sysmgt.serv_aid. This fileset is not automatically installed by earlier releases
of AIX Version 4. Use the following command to check whether the package is
installed on your system:
# lslpp -l bos.sysmgt.serv_aid
Fileset
Level State
Description
-------------------------------------------------------------------------Path: /usr/lib/objrepos
bos.sysmgt.serv_aid
4.3.3.0 COMMITTED Software Error Logging and
Dump Service Aids
Path: /etc/objrepos
bos.sysmgt.serv_aid
4.3.3.0
COMMITTED
Software Error Logging and
Dump Service Aids
Managing the error log
Error logging is automatically started during system initialization by the
/sbin/rc.boot script and is automatically stopped during system shutdown by the
shutdown script. The part of /sbin/rc.boot that starts error logging looks like:
if [ -x /usr/lib/errdemon ]
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
then
echo "Starting the error daemon" | alog -t boot
/usr/bin/rm -f /tmp/errdemon.$$
/usr/lib/errdemon >/tmp/errdemon.$$ 2>&1
if [ $? -ne 0 ]
then
cat /tmp/errdemon.$$ | alog -t boot
echo "Starting the errdemon with the system default" \
"log file, /var/adm/ras/errlog." | alog -t boot
/usr/lib/errdemon -i /var/adm/ras/errlog
fi
/usr/bin/rm -f /tmp/errdemon.$$
fi
As you can see, the /usr/lib/errdemon command starts error logging and
initializes /var/adm/ras/errlog as a default log file.
Configuring error log
You can customize the name and location of the error log file and the size of the
internal error buffer to suit your needs.
To list the current settings, run the /usr/lib/errdemon -l command. The values
for the error log file name, error log file size, and buffer size that are currently
stored in the error log configuration database are displayed on your screen.
# /usr/lib/errdemon -l
Error Log Attributes
-------------------------------------------Log File
/var/adm/ras/errlog
Log Size
1048576 bytes
Memory Buffer Size
8192 bytes
You can change all of values listed above:
 To change the name of the file used for error logging, run:
# /usr/lib/errdemon -i /var/adm/ras/errlog.new
The /var/adm/ras/errlog.new file name is saved in the error log configuration
database and the error daemon is immediately restarted.
 To change the maximum size of the error log file to 2000000 bytes, type:
# /usr/lib/errdemon -s 2000000
The specified log file size limit is saved in the error log configuration database
and the error daemon is immediately restarted.
Appendix A. The error log
289
 To change the size of the error log device driver's internal buffer to 16384
bytes, enter:
# /usr/lib/errdemon -B 16384
0315-175 The error log memory buffer size you supplied will be rounded up
to a multiple of 4096 bytes.
The specified buffer size is saved in the error log configuration database and,
if it is larger than the buffer size currently in use, the in-memory buffer is
immediately increased. The size you specify is rounded up to the next integral
multiple of the memory page size (4 KBs).
Note: The memory used for the error log device driver's in-memory buffer
is not available for use by other processes (the buffer is pinned).
Now verify what you did with the following command. Note the highlighted values
reflect the changes you made:
# /usr/lib/errdemon -l
Error Log Attributes
-------------------------------------------Log File
/var/adm/ras/errlog.new
Log Size
2000000 bytes
Memory Buffer Size
16384 bytes
Clearing the error log
Clearing of the error log implies deleting old or unnecessary entries from the
error log. Clearing is normally done as part of the daily cron command execution.
To check it, type:
# crontab -l | grep errclear
0 11 * * * /usr/bin/errclear -d S,O 30
0 12 * * * /usr/bin/errclear -d H 90
If it is not done automatically, you should probably clean the error log regularly.
To delete all the entries from the error log, use the following command:
# errclear 0
To selectively remove entries from the error log, for example, to delete all
software error entries, use the following command:
# errclear -d S 0
To selectively remove entries from the error log, for example, to delete all
hardware error entries, use the following command:
# errclear -d H 0
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Alternatively, use the smitty errclear command.
Reading error logs in details
You can generate an error report from data collected in the error log. There are
two main ways to view the error log:
 The easiest way to read the error log entries is with the smitty errpt
command. Output from this command is shown in Figure A-1.
Figure A-1 smitty errpt output
 The second way to display error log entries is with the errpt command. It
allows flags for selecting errors that match specific criteria. By using the
default condition, you can display error log entries in the reverse order they
occurred and were recorded.
The errpt command output
By using the -c flag, you can display errors as they occur. The default summary
report contains one line of data for each error:
# errpt | pg
IDENTIFIER TIMESTAMP T C RESOURCE_NAME
2BFA76F6
0627172400 T S SYSPROC
9DBCFDEE
0627172700 T O errdemon
DESCRIPTION
SYSTEM SHUTDOWN BY USER
ERROR LOGGING TURNED ON
Appendix A. The error log
291
192AC071
1581762B
1581762B
1581762B
1581762B
E18E984F
E18E984F
0627172300
0627132600
0627132000
0627131900
0627131900
0627100000
0627095400
T
T
T
T
T
P
P
O
H
H
H
H
S
S
errdemon
cd0
cd0
cd0
cd0
SRC
SRC
ERROR LOGGING TURNED OFF
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
The fields used in this report are discussed in the following sections.
Identifier
Numerical identifier for the event.
Timestamp
Time when the error occurs in format mmddhhmmyy. The timestamp
0627172400 indicates that the error occur June 27th at 17:24 (5:24 p.m.) year 00
(year 2000).
Type
Severity of the error that has occurred. There are six possible values:
PEND
The loss of availability of a device or component is imminent.
PERF
The performance of the device or component has degraded to below
an acceptable level.
PERM
A condition has occurred that could not be recovered from. Error types
with this value are usually the most severe errors and are more likely to
mean that you have a defective hardware device or software module.
Error types other than PERM usually do not indicate a defect, but they
are recorded so that they can be analyzed by the diagnostics
programs.
TEMP
A condition occurred that was recovered from after a number of
unsuccessful attempts.
UNKN
It is not possible to determine the severity of the error.
INFO
The error log entry is informational and was not the result of an error.
Class
General source of the error. The possible error classes are:
292
H
Hardware. When you receive a hardware error, refer to your system
operator guide for information about performing diagnostics on the
problem device or other piece of equipment.
S
Software.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
O
Informational messages.
U
Undetermined (for example, network).
Resource name
For software errors, this is the name of a software component or an executable
program. For hardware errors, this is the name of a device or system component.
It is used to determine the appropriate diagnostic modules that are to be used to
analyze the error.
Description
A brief summary of the error.
Formatted output from errpt command
The following list provides a series of format options for the errpt command.
 To list all hardware errors, enter:
# errpt -d
IDENTIFIER
1581762B
1581762B
1581762B
1581762B
5BF9FD4D
2A9F5252
2A9F5252
2A9F5252
5BF9FD4D
2A9F5252
2A9F5252
2A9F5252
2A9F5252
H
TIMESTAMP
0627132600
0627132000
0627131900
0627131900
0615173700
0615161700
0615161600
0615161600
0615155900
0615151400
0615151300
0615151300
0615151300
T
T
T
T
T
T
P
P
P
T
P
P
P
P
C
H
H
H
H
H
H
H
H
H
H
H
H
H
RESOURCE_NAME
cd0
cd0
cd0
cd0
tok0
tok0
tok0
tok0
tok0
tok0
tok0
tok0
tok0
DESCRIPTION
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
PROBLEM RESOLVED
WIRE FAULT
WIRE FAULT
WIRE FAULT
PROBLEM RESOLVED
WIRE FAULT
WIRE FAULT
WIRE FAULT
WIRE FAULT
 To get a detailed report of all software errors, enter:
# errpt -a -d S | pg
----------------------------------------------------------------------LABEL:
REBOOT_ID
IDENTIFIER:
2BFA76F6
Date/Time:
Sequence Number:
Machine Id:
Node Id:
Class:
Type:
Resource Name:
Tue Jun 27 17:24:55
33
006151424C00
server4
S
TEMP
SYSPROC
Appendix A. The error log
293
Description
SYSTEM SHUTDOWN BY USER
Probable Causes
SYSTEM SHUTDOWN
Detail Data
USER ID
0
0=SOFT IPL 1=HALT 2=TIME REBOOT
0
TIME TO REBOOT (FOR TIMED REBOOT ONLY)
0
----------------------------------------------------------------------...
 To display a report of all errors logged for the error identifier E18E984F,
enter:
# errpt -j
IDENTIFIER
E18E984F
E18E984F
E18E984F
E18E984F
E18E984F
E18E984F
E18E984F
TIMESTAMP
0627100000
0627095400
0627093000
0626182100
0626181400
0626130400
T
P
P
P
P
P
P
C
S
S
S
S
S
S
RESOURCE_NAME
SRC
SRC
SRC
SRC
SRC
SRC
DESCRIPTION
SOFTWARE PROGRAM
SOFTWARE PROGRAM
SOFTWARE PROGRAM
SOFTWARE PROGRAM
SOFTWARE PROGRAM
SOFTWARE PROGRAM
ERROR
ERROR
ERROR
ERROR
ERROR
ERROR
 To display a report of all errors that occur after June 26, 2000 at 18:14 (time),
enter:
# errpt -s
IDENTIFIER
2BFA76F6
9DBCFDEE
192AC071
1581762B
1581762B
1581762B
1581762B
E18E984F
E18E984F
E18E984F
2BFA76F6
9DBCFDEE
192AC071
369D049B
SYSTEM
E18E984F
E18E984F
294
0626181400
TIMESTAMP
0627172400
0627172700
0627172300
0627132600
0627132000
0627131900
0627131900
0627100000
0627095400
0627093000
0627092700
0627092900
0627092500
0626183400
T
T
T
T
T
T
T
T
P
P
P
T
T
T
I
C
S
O
O
H
H
H
H
S
S
S
S
O
O
O
RESOURCE_NAME
SYSPROC
errdemon
errdemon
cd0
cd0
cd0
cd0
SRC
SRC
SRC
SYSPROC
errdemon
errdemon
SYSPFS
0626182100 P S SRC
0626181400 P S SRC
DESCRIPTION
SYSTEM SHUTDOWN BY USER
ERROR LOGGING TURNED ON
ERROR LOGGING TURNED OFF
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
DISK OPERATION ERROR
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
SYSTEM SHUTDOWN BY USER
ERROR LOGGING TURNED ON
ERROR LOGGING TURNED OFF
UNABLE TO ALLOCATE SPACE IN FILE
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 To obtain all the errors with resource name cd0 from the error log, enter:
# errpt -N
IDENTIFIER
1581762B
1581762B
1581762B
1581762B
cd0
TIMESTAMP
0627132600
0627132000
0627131900
0627131900
T
T
T
T
T
C
H
H
H
H
RESOURCE_NAME
cd0
cd0
cd0
cd0
DESCRIPTION
DISK OPERATION
DISK OPERATION
DISK OPERATION
DISK OPERATION
ERROR
ERROR
ERROR
ERROR
 The -c flag formats and displays each of the error entries concurrently, that is,
at the time they are logged. The existing entries in the log file are displayed in
the order in which they were logged. An example below:
# errpt -c
IDENTIFIER
9DBCFDEE
2BFA76F6
FFE305EE
75CE5DC5
E18E984F
E18E984F
E18E984F
FFE305EE
TIMESTAMP
0823160702
0823160002
0823160702
0823160702
0823160802
0823160802
0823160802
0823160802
T
T
T
P
I
P
P
P
P
C
O
S
H
H
S
S
S
H
RESOURCE_NAME
errdemon
SYSPROC
tok0
tok0
SRC
SRC
SRC
tok0
DESCRIPTION
ERROR LOGGING TURNED ON
SYSTEM SHUTDOWN BY USER
WIRE FAULT
ADAPTER ERROR
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
SOFTWARE PROGRAM ERROR
WIRE FAULT
Command summary
The following section discusses the errpt command.
The errpt command
The errpt command generates an error report from entries in an error log. The
command has the following syntax:
errpt [ -a ] [ -c ] [ -d ErrorClassList ] [ -e EndDate ] [ -j ErrorID ]
[ -s StartDate ] [ -N ResourceNameList ] [ -S ResourceClassList ]
[ -T ErrorTypeList ]
The commonly used flags are listed in Table A-1.
Table A-1 Commonly used flags of the errpt command
Flag
Description
-a
Displays information about errors in the error log file in detailed
format.
-c
Formats and displays each of the error entries concurrently, that is,
at the time they are logged. The existing entries in the log file are
displayed in the order in which they were logged.
Appendix A. The error log
295
Flag
Description
-d
ErrorClassList
Limits the error report to certain types of error records specified by
the valid ErrorClassList variables: H (hardware), S (software), 0
(errlogger command messages), and U (undetermined).
-e EndDate
Specifies all records posted prior to and including the EndDate
variable.
-j ErrorID
Includes only the error-log entries specified by the ErrorID (error
identifier) variable.
-s StartDate
Specifies all records posted on and after the StartDate variable.
-N
ResourceNam
eList
Generates a report of resource names specified by the
ResourceNameList variable. The ResourceNameList variable is a
list of names of resources that have detected errors.
-S
ResourceClas
sList
Generates a report of resource classes specified by the
ResourceClassList variable.
-T
ErrorTypeList
Limits the error report to error types specified by the valid
ErrorTypeList variables: INFO, PEND, PERF, PERM, TEMP, and
UNKN.
Quiz
The following assessment question helps verify your understanding of the topics
discussed in this appendix.
1. Which of the following commands should be used to list the system errors
logged following February 29, 2000?
A.
/usr/bin/errpt -s 0301000000
B.
/usr/bin/lssrc -s 0301000000
C. /usr/lib/errdemon -s 0301000000
D.
296
/usr/sbin/syslogd -m 0301000000
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Answers
The following is the preferred answer to the question provided in this section.
1. A
Exercises
The following exercises provide sample topics for self study. They will help
ensure comprehension of this appendix.
1. Change the default error log attributes.
2. Using the errpt command, generate a report of errors caused by the
errdemon resource.
3. Using the errpt command, generate a report of software errors, but limit it to
temporary errors.
4. Generate the same reports using the smitty tool.
5. Delete all software logs.
Appendix A. The error log
297
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
B
Appendix B.
Installing the performance
tools
Anyone faced with the task of keeping a computer system well tuned and
capable of performing as expected recognizes the following areas as essential
for success:
Load monitoring
Resource load must be monitored so performance
problems can be detected as they occur or (preferably)
predicted before they do.
Analysis and control Once a performance problem is encountered, the proper
tools must be selected and applied so that the nature of
the problem can be understood and corrective action
taken.
Capacity planning
© Copyright IBM Corp. 2002. All rights reserved.
Long-term capacity requirements must be analyzed so
that sufficient resources can be acquired before they are
required.
299
Tools and filesets
The intention of this section is to give you a list of all the performance tools
discussed in this book together with the path that is used to call the command
and the fileset the tool is part of.
Many of the performance tools are located in filesets that obviously would
contain them, such as bos.perf.tools or perfagent.tools. However, some of them
are located in filesets that are not quite as obvious. Common examples are
vmtune or schedtune, which are both part of the bos.adt.samples fileset. You will
often find that this fileset is not installed on a system because it does not contain
performance tools.
Table B-1 lists the tools discussed in this book, their full path names, and their
fileset information.
Table B-1 Commands or tools, path names, and filesets
Command or tool
Full path name
Fileset name/URL
3dmon
/usr/bin/3dmon
perfmgr.network
alstat
/usr/bin/alstat
bos.perf.tools
atmstat
/usr/bin/atmstat
devices.common.IBM.atm.rte
bindintcpu
/usr/sbin/bindintcpu
devices.chrp.base.rte
bindprocessor
/usr/sbin/bindprocessor
bos.mp
curt
-
ftp://software.ibm.com/
emstat
/usr/bin/emstat
bos.perf.tools
entstat
/usr/bin/entstat
devices.common.IBM.ethernet.rte
estat
/usr/lpp/ssp/css/css
ssp.css
fddistat
/usr/bin/fddistat
devices.common.IBM.fddi.rte
fdpr
/usr/bin/fdpr
perfagent.tools
filemon
/usr/bin/filemon
bos.perf.tools
fileplace
/usr/bin/fileplace
bos.perf.tools
genkex
/usr/bin/genkex
bos.perf.tools
genkld
/usr/bin/genkld
bos.perf.tools
genld
/usr/bin/genld
bos.perf.tools
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Command or tool
Full path name
Fileset name/URL
gennames
/usr/bin/gennames
bos.perf.tools
gprof
/usr/bin/gprof
bos.adt.prof
iostat
/usr/bin/iostat
bos.acct
ipcs
/usr/bin/ipcs
bos.rte.control
ipfilter
/usr/bin/ipfilter
bos.perf.tools
ipreport
/usr/sbin/ipreport
bos.net.tcp.server
iptrace
/usr/sbin/iptrace
bos.net.tcp.server
jazizo (PTX)
/usr/bin/jazizo
perfmgr.analysis.jazizo
locktrace
/usr/bin/locktrace
bos.perf.tools
lslv
/usr/sbin/lslv
bos.rte.lvm
lspv
/usr/sbin/lspv
bos.rte.lvm
lsvg
/usr/sbin/lsvg
bos.rte.lvm
lvmstat
/usr/sbin/lvmstat
bos.rte.lvm
netpmon
/usr/bin/netpmon
bos.perf.tools
netstat
/usr/bin/netstat
bos.net.tcp.client
nfso
/usr/sbin/nfso
bos.net.nfs.client
nfsstat
/usr/sbin/nfsstat
bos.net.nfs.client
nice
/usr/bin/nice
bos.rte.control
no
/usr/sbin/no
bos.net.tcp.client
PDT
/usr/sbin/perf/diag_tool
bos.perf.diag_tool
perfpmr
-
ftp://software.ibm.com/
Perfstat API
-
bos.perf.libperfstat
PM API
-
bos.pmapi.lib
pprof
/usr/bin/pprof
bos.perf.tools
prof
/usr/bin/prof
bos.adt.prof
ps
/usr/bin/ps
bos.rte.control
renice
/usr/bin/renice
bos.rte.control
Appendix B. Installing the performance tools
301
Command or tool
Full path name
Fileset name/URL
RMC
-
rsct.*
rmss
/usr/bin/rmss
bos.perf.tools
sar
/usr/sbin/sar
bos.acct
schedtune
/usr/samples/kernel/schedtune
bos.adt.samples
splat
-
ftp://software.ibm.com/
SPMI API
-
perfagent.tools, perfagent.server
stripnm
/usr/bin/stripnm
bos.perf.tools
svmon
/usr/bin/svmon
bos.perf.tools
tcpdump
/usr/sbin/tcpdump
bos.net.tcp.server
time
/usr/bin/time
bos.rte.misc_cmds
timex
/usr/bin/timex
bos.acct
tokstat
/usr/bin/tokstat
devices.common.IBM.tokenring.rte
topas
/usr/bin/topas
bos.perf.tools
tprof
/usr/bin/tprof
bos.perf.tools
trace
/usr/bin/trace
bos.sysmgt.trace
trcnm
/usr/bin/trcnm
bos.sysmgt.trace
trcrpt
/usr/bin/trcrpt
bos.sysmgt.trace
trpt
/usr/sbin/trpt
bos.net.tcp.server
truss
/usr/bin/truss
bos.sysmgt.serv_aid
vmstat
/usr/bin/vmstat
bos.acct
vmtune
/usr/samples/kernel/vmtune
bos.adt.samples
wlmmon
/usr/bin/wlmmon
perfagent.tools
wlmperf
/usr/bin/wlmperf
perfmgr.analysis.jazizo
wlmstat
/usr/sbin/wlmstat
bos.rte.control
xmperf (PTX)
/usr/bin/xmperf
perfmgr.network
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Tools by resource matrix
This section contains a table of the AIX monitoring and tuning tools (Table B-2)
and what system resources (CPU, memory, disk I/O, network I/O) they obtain
statistics for. Tools that are used by trace, that post-process the trace output, or
that are directly related to trace are listed in the Trace tools column. Tools that
are useful for application development are listed in the Application development
column.
Table B-2 Performance tools by resource matrix
Command
alstat
CPU
Memory
Disk
I/O
Network
I/O
Trace
tools
x
atmstat
x
bindintcpu
x
bindprocessor
x
curt
x
emstat
x
x
entstat
x
estat
x
fddistat
x
fdpr
x
filemon
x
fileplace
x
x
genkex
x
genkld
x
genld
x
gennames
x
gprof
x
iostat
x
ipcs
ipfilter
Application
Development
x
x
x
x
x
Appendix B. Installing the performance tools
303
Command
CPU
Memory
Disk
I/O
ipreport
x
iptrace
x
locktrace
x
x
lspv
x
lsvg
x
lvmstat
x
x
x
netstat
x
nfso
x
nfsstat
x
nice
Trace
tools
Application
Development
x
lslv
netpmon
x
x
no
x
PDT
x
x
x
x
perfpmr
x
x
x
x
Perfstat API
x
x
x
x
PM API
x
pprof
x
prof
x
ps
x
x
PTX
x
x
x
x
renice
x
RMC
x
x
x
x
x
x
rmss
304
Network
I/O
x
x
x
x
x
sar
x
x
schedtune
x
x
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
x
Command
CPU
splat
x
SPMI API
x
Memory
x
Disk
I/O
x
Network
I/O
Trace
tools
Application
Development
x
x
x
x
x
stripnm
svmon
x
tcpdump
x
time
x
timex
x
tokstat
x
topas
x
tprof
x
trace
x
x
x
x
x
x
x
x
trcnm
x
trcrpt
x
trpt
x
truss
vmstat
x
x
x
vmtune
x
x
x
wlmmon
x
x
x
x
wlmperf
x
x
x
x
wlmstat
x
x
x
x
The bos.perf package, part of the base operating system, contains the
bos.perf.diag_tool fileset with the performance diagnostic tool. Performance
PMR data collection scripts were removed from this fileset in AIX Version 4.3.3.
They are available from the IBM support download Web site. In AIX 5L Version
5.1, the bos.perf.diag_tool fileset is part of base operating system.
Appendix B. Installing the performance tools
305
Performance Toolbox
The Performance Toolbox is a Motif-based, AIX Licensed Program Product
(LPP) that consolidates AIX performance tools in a toolbox framework. Users
can easily access tools for system and network performance tuning, monitoring,
and analysis. It consists of two major components: Performance Toolbox
Manager and Performance Toolbox Agent. The Performance Toolbox Manager
has three packages:
perfmgr.local
This package contains the commands and utilities that
allow monitoring of only the local system.
perfmgr.network
This package contains the commands and utilities that
allow monitoring of remote systems as well as the local
system.
perfmgr.common
This package contains the commands and utilities that
are common between the network support and the local
support.
The Performance Toolbox Agent has one package:
perfagent.server
This package contains the performance agent component
required by Performance Toolbox as well as some local
AIX analysis and control tools.
The packaging of the older levels of the Performance Toolbox contained two
system-level dependant filesets named perfagent.server and perfagent.tool,
causing installation misunderstandings. To reduce confusion over operating
system compatibility, the pieces that are required to be built with the AIX kernel
have been moved into the perfagent.tools fileset. The agent is now, mainly, an
interface routine to those pieces.
Starting with AIX Version 4.3.2, the perfagent.tools fileset is shipped with the
base. For AIX Version 4.3.2 and above, the Performance Toolbox Agent will
require perfagent.tools as a prerequisite. Therefore, the tools fileset must be
installed first.
Table B-3 lists the various minimum fileset levels required with a particular AIX
level.
Table B-3 Performance Toolbox releases
306
AIX version
Performance Agent
Performance Manager
AIX 4.1.5
perfagent 2.1.6.0
perfmgr 2.2.1.0
perfmgr.common 2.2.1.2
perfmgr.local 2.2.1.4
perfmgr.network 2.2.1.4
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
AIX version
Performance Agent
Performance Manager
AIX 4.2.1
perfagent 2.2.1.0
perfmgr 2.2.1.0
perfmgr.common 2.2.1.2
perfmgr.local 2.2.1.4
perfmgr.network 2.2.1.4
AIX 4.3.1
perfagent.tools 2.2.31.0
perfmgr 2.2.1.0
perfmgr.common 2.2.1.2
perfmgr.local 2.2.1.4
perfmgr.network 2.2.1.4
AIX 4.3.2
perfagent.tools 2.2.32.0
perfagent.server 2.2.32.0
perfmgr 2.2.1.0
perfmgr.common 2.2.1.2
perfmgr.local 2.2.1.4
perfmgr.network 2.2.1.4
AIX 4.3.3
perfagent.tools 2.2.33.82
perfagent.server 2.2.32.10
perfmgr 2.2.1.10
perfmgr.common 2.2.1.10
perfmgr.local 2.2.1.10
perfmgr.network 2.2.1.10
AIX 5.1.0
perfagent.tools 5.1.0.27
perfagent.server 3.0.0.0
perfmgr.common 3.0.0.0
perfmgr.network 3.0.0.0
As listed, the Performance Manager releases remain the same throughout AIX
Version 4.1.5 to 4.3.3. However, you should choose the correct version of the
Agent component, because it will only work properly when installed on the
correct level of AIX.
Before you install Performance Toolbox software, you have to determine the AIX
and the maintenance level of your system. To determine the AIX and
maintenance level of the system, enter the following command:
# oslevel
5.1.0.0
The current maintenance level of the system shown in this example is 5.1.0.0. To
list the names of known maintenance levels, use the following command:
# oslevel -q
Known Maintenance Levels
-----------------------5.1.0.0
5.0.0.0
To determine the filesets at levels later than the current AIX maintenance level,
enter:
# oslevel -g|more
Appendix B. Installing the performance tools
307
Fileset
Actual Level
Maintenance Level
----------------------------------------------------------------------------IMNSearch.bld.DBCS
2.3.1.15
2.3.1.0
IMNSearch.bld.SBCS
2.3.1.15
2.3.1.0
IMNSearch.rte.com
2.3.1.15
2.3.1.0
IMNSearch.rte.httpdlite
2.0.0.15
2.0.0.2
Java130.rte.bin
1.3.0.14
1.3.0.5
Java130.rte.lib
1.3.0.14
1.3.0.5
X11.Dt.ToolTalk
5.1.0.15
5.1.0.0
.....
.....
Another command that can be used to determine the software levels installed is
the instfix command. To list the names of installed maintenance levels on
another server with AIX5L Version 5.1 installed, use the following command:
# instfix -i |grep ML
All filesets for 5.0.0.0_AIX_ML
All filesets for 5.1.0.0_AIX_ML
All filesets for 5.1.0.0_AIX_ML
All filesets for 5100-01_AIX_ML
All filesets for 5100-02_AIX_ML
were
were
were
were
were
found.
found.
found.
found.
found.
The instfix command allows you to install a fix or set of fixes without knowing
any information other than the Authorized Program Analysis Report (APAR)
number. The instfix command also allows you to determine if a fix is installed
on your system.
The oslevel command reports the level of the operating system using a subset
of all filesets installed on you system. These filesets include the Base Operating
System (BOS), and the device drivers and base printers. The oslevel command
also prints information about maintenance levels, including which filesets are not
at a specified maintenance level.
To check if any of the Performance Toolbox packages are installed, use the
following command:
# lslpp -l perf*
Fileset
Level State
Description
---------------------------------------------------------------------------Path: /usr/lib/objrepos
5.1.0.25
5.1.0.0
perfagent.server
3.0.0.0 COMMITTED Performance Agent Daemons &
Utilities
perfmgr.common
3.0.0.0 COMMITTED Performance Toolbox Manager Common Support
perfmgr.network
3.0.0.0 COMMITTED Performance Toolbox Manager Network Support
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Path: /etc/objrepos
perfagent.server
3.0.0.0
COMMITTED
Performance Agent Daemons &
Utilities
You can receive similar information using the smitty list_software command.
The output is shown in Figure B-1.
Figure B-1 smitty list_software output
If you are missing some filesets and have media containing the Performance
Toolbox software, you can check what it contains. You can use either the
installp command or smitty. The Web-based System Manager is an additional
tool for system administration and is the strategic interface.
The output from the installp command appears as follows:
# installp -ld . -I
Fileset Name
Level
I/U Q Content
====================================================================
perfagent.server
3.0.0.0
I N usr,root
#
Performance Agent Daemons & Utilities
perfmgr.common
3.0.0.0
Performance Toolbox Manager - Common Support
I
N usr
#
perfmgr.network
3.0.0.0
Performance Toolbox Manager - Network Support
I
N usr
#
Appendix B. Installing the performance tools
309
This indicates that the media contains both components: The Performance
Toolbox Manager and the Performance Toolbox Agent.
The next step is to install the Performance Toolbox. The most direct way to install
software is with the smitty install_all command, as shown in Figure B-2.
Figure B-2 smitty install_all
Do not commit software until you are sure that the installation process does not
impact the system. After installation, check the $HOME/smit.log file for errors
and run the lppchk command to verify a successful installation process. If
everything is normal, you can commit your installation with the installp -c all
command. Or use SMIT as shown below:
# smitty commit
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Figure B-3 Commit software updates
Clean up any failed installation with the installp -C command.
For example, to check that you have the filesets installed for both the manager
and agent part, perform the following steps (a server with AIX Version 4.3.3 was
used).
For the agent, enter the following command:
# lslpp -l perfagent.*
Fileset
Level State
Description
-------------------------------------------------------------------------Path: /usr/lib/objrepos
perfagent.html.en_US.usergd
4.3.0.0 COMMITTED Performance Toolbox Guides U. S. English
perfagent.server
2.2.32.3 APPLIED
Performance Agent Daemons &
Utilities
perfagent.tools
2.2.34.0 COMMITTED Local Performance Analysis&
Control Commands
Path: /etc/objrepos
perfagent.server
2.2.30.0
COMMITTED
Performance Agent Daemons &
Utilities
Appendix B. Installing the performance tools
311
For the manager, enter the following command:
# lslpp -l perfmgr.*
Fileset
Level State
Description
-------------------------------------------------------------------------Path: /usr/lib/objrepos
perfmgr.common
2.2.1.5 APPLIED
Performance Toolbox Manager
Common Support
perfmgr.local
2.2.1.7 APPLIED
Performance Toolbox Manager
Local Support
perfmgr.network
2.2.1.7 APPLIED
Performance Toolbox Manager
Network Support
Examine what is inside the filesets that you installed. This completes the
installation:
# lslpp -f perfmgr.local
Fileset
File
-------------------------------------------------------------------------Path: /usr/lib/objrepos
perfmgr.local 2.2.1.0
/usr/lpp/perfmgr/local/bin
/usr/lpp/perfmgr/local/bin/3dmon
/usr/lpp/perfmgr
/usr/lpp/perfmgr/local/bin/exmon
/usr/lpp/perfmgr/local
/usr/lpp/perfmgr/local/bin/xmperf
/usr/lpp/perfmgr/README.perfmgr.local
/usr/lpp/perfmgr/local/bin/ptxrlog
Another tool used by IBM support personnel is perfpmr, a collection facility that
uses standard AIX performance commands. Go to the following site and follow
the readme file for further instructions on how to install this utility:
ftp://ftp.software.ibm.com/aix/tools/perftools/perfpmr/perf51/
Command summary
The following section provides a list of the key commands discussed in this
appendix.
The installp command
The installp command is a very useful and powerful software installation tool.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
To install with apply only or with apply and commit:
installp [ -a |
[ -S ] [ -B ] [
[-F | -g ] [ -O
[ -zBlockSize ]
-ac [ -N ] ] [ -eLogFile ] [ -V Number ] [ -dDevice ] [ -b ]
-D ] [ -I ] [ -p ] [ -Q ] [ -q ] [ -v ] [ -X ]
{ [ r ] [ s ] [ u ] } ] [ -tSaveDirectory ] [ -w ]
{ FilesetName [ Level ]... | -f ListFile | all }
To commit applied updates:
installp -c [ -eLogFile ] [ -VNumber ] [ -b ] [ -g ] [ -p ] [ -v ]
[ -X ] [ -O { [ r ] [ s ] [ u ] } ] [ -w ] { FilesetName [ Level ]... | -f
ListFile | all }
To reject applied updates:
installp -r [ -eLogFile ] [ -VNumber ] [ -b ] [ -g ] [ -p ] [ -v ] [ -X ]
[ -O { [ r ] [ s ] [ u ] } ] [ -w ] { FilesetName [ Level ]... |
-f ListFile }
To uninstall (remove) installed software:
installp -u [ -eLogFile ] [ -VNumber ] [ -b ] [ -g ] [ -p ] [ -v ] [ -X ]
[ -O { [ r ] [ s ] [ u ] } ] [ -w ] { FilesetName [ Level ]... |
-f ListFile }
To clean up a failed installation:
installp -C [ -b ] [ -eLogFile ]
To list all installable software on a selected media:
installp { -l | -L } [ -eLogFile ] [ -dDevice ] [ -B ] [ -I ] [ -q ]
[ -zBlockSize ] [ -O { [ s ] [ u ] } ]
To list all customer-reported problems fixed with software or display all
supplemental information:
installp { -A | -i } [ -eLogFile ] [ -dDevice ] [ -B ] [ -I ] [ -q ]
[ -z BlockSize ] [ -O { [ s ] [ u ] } ] { FilesetName [ Level ]... | -f
ListFile | all }
To list installed updates that are applied but not committed:
installp -s [ -eLogFile ] [ -O { [ r ] [ s ] [ u ] } ] [ -w ]
{ FilesetName [ Level ]... | -fListFile | all }
Table B-4 provides a general summary of some useful installp flags.
Table B-4 General installp summary
Flag
Description
-ac
Commits
Appendix B. Installing the performance tools
313
Flag
Description
-g
Includes requisites
-N
Overrides saving of existing files
-q
Quiet mode
-w
Does not place a wildcard at end of fileset name
-X
Attempts to expand file system size if needed
-d
Inputs device
-l
Lists installable filesets
-c
Commits an applied fileset
-C
Cleans up after an failed installation
-u
Uninstalls
-r
Rejects an applied fileset
-p
Previews installation
-e
Defines an installation log
-F
Forces overwrite of same or newer version
The lslpp command
The lslpp command displays information about installed filesets or fileset
updates. The command has the following syntax:
lslpp { -f | -h | -i | -L } ] [ -a ] [ FilesetName ... | FixID ... | all ]
Table B-5 provides a general summary of some useful lslpp flags.
Table B-5 Commonly used flags of the lslpp command
314
Flag
Description
-a
Displays all the information about filesets specified when combined
with other flags.
-f
Displays the names of the files added to the system during installation
of the specified fileset. This flag cannot be specified with the -a flag.
-h
Displays the installation and update history information for the
specified fileset.
-i
Displays the product information for the specified fileset.
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Flag
Description
-L
Displays the name, most recent level, state, and description of the
specified fileset. Part of the information (usr, root, and share) is
consolidated into the same listing.
-w
Lists fileset that owns this file.
The lppchk command
The lppchk command verifies files of an installable software product. The
command has the following syntax:
lppchk { -c | -f | -l | -v } [ -O { [ r ] [ s ] [ u ] } ]
[ ProductName [ FileList ... ] ]
Table B-6 provides a general summary of some useful lppchk flags.
Table B-6 Commonly used flags of the lppchk command
Flag
Description
-c
Performs a checksum operation on the FileList items and verifies
that the checksum and the file size are consistent with the SWVPD
database.
-f
Checks that the FileList items are present and the file size matches
the SWVPD database.
-l
Verifies symbolic links for files as specified in the SWVPD database.
-O {[r] [s] [u]}
Verifies the specified parts of the program. The flags specify the
following parts: root, share, usr.
Appendix B. Installing the performance tools
315
Quiz
The following assessment questions help verify your understanding of the topics
discussed in this appendix.
1. Which of the following commands should be used to obtain information about
the level of the operating system and conformance with maintenance levels?
A.
lslpp
B.
uname
C. oslevel
D.
rpcinfo
2. Which of the following commands should be used to obtain information about
the installed software filesets?
A.
lslpp
B.
uname
C. oslevel
D.
rpcinfo
3. Which of the following commands should be used to obtain information about
the fixes available on some media?
A.
installp -Ad . all
B.
/usr/sbin/inutoc .
C. lsresource -dl rmt0
D.
/usr/sbin/lsattr -Dl rmt0
4. Which of the following commands should be used to commit applied filesets?
A.
/usr/sbin/lsattr
B.
/usr/sbin/inutoc
C. /usr/sbin/installp
D.
/usr/sbin/lsresource
5. An AIX Version 4.3 system must be evaluated and tuned. In order to use a set
of performance tools (for example, filemon, svmon, and tprof) which of the
following packages should exist on the system in question?
A.
Java.adt
B.
bos.perf
C. bos.adt.utils
D.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
6. Which of the following packages once contained the Performance PMR Data
Collection scripts (removed in AIX Version 4.3.3, although they are available
for download from the perfpmr site)?
A.
bos.perf
B.
Java.adt
C. bos.adt.utils
D.
perfagent.tools
7. Which of the following resources will provide the latest available performance
data capture tools?
A.
The system’s software depositories
B.
The IBM support download Web site
C. The standard documentation included with the system
D.
The software distribution media included with the system
8. Which of the following filesets is used to install tprof?
A.
bos.acct
B.
bos.perf.pmr
C. bos.rte.control
D.
perfagent.tools
9. The components xmperf, 3dmon, and 3dplay are part of the Performance
Toolbox contained in which of the following packages?
A.
perfmgr
B.
perfagent.server
C. perfagent.tools
D.
perfagent.client
Appendix B. Installing the performance tools
317
Answers
The following are the preferred answers to the questions provided in this section.
1. C
2. A
3. A
4. C
5. D
6. A
7. B
8. D
9. A
Exercises
The following exercises provide sample topics for self study. They will help
ensure comprehension of this appendix.
1. Use the lslpp command to list installed filesets.
2. Use the lslpp command to find out which fileset is used to package a given
command.
3. Use the lslpp command to display state, description, and all updates of the
different filesets.
4. Use the oslevel command to determine the filesets at levels later than the
current AIX maintenance level.
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Abbreviations and acronyms
ABI
Application Binary Interface
BIST
Built-In Self-Test
AC
Alternating Current
BLAS
ACL
Access Control List
Basic Linear Algebra
Subprograms
ADSM
ADSTAR Distributed Storage
Manager
BLOB
Binary Large Object
BLV
Boot Logical Volume
ADSTAR
Advanced Storage and
Retrieval
BOOTP
Boot Protocol
BOS
Base Operating System
AFPA
Adaptive Fast Path
Architecture
BSC
Binary Synchronous
Communications
AFS
Andrew File System
CAD
Computer-Aided Design
AH
Authentication Header
CAE
Computer-Aided Engineering
AIX
Advanced Interactive
Executive
CAM
Computer-Aided
Manufacturing
ANSI
American National Standards
Institute
CATE
Certified Advanced Technical
Expert
APAR
Authorized Program Analysis
Report
CATIA
API
Application Programming
Interface
Computer-Graphics Aided
Three-Dimensional
Interactive Application
CCM
Common Character Mode
ARP
Address Resolution Protocol
CD
Compact Disk
ASCI
Accelerated Strategic
Computing Initiative
CDE
Common Desktop
Environment
ASCII
American National Standards
Code for Information
Interchange
CDLI
Common Data Link Interface
CD-R
CD Recordable
ASR
Address Space Register
CD-ROM
ATM
Asynchronous Transfer Mode
Compact Disk-Read Only
Memory
AuditRM
Audit Log Resource Manager
CE
Customer Engineer
AUI
Attached Unit Interface
CEC
Central Electronics Complex
AWT
Abstract Window Toolkit
CFD
Computational Fluid
Dynamics
BCT
Branch on CounT
CGE
BFF
Backup File Format
Common Graphics
Environment
BI
Business Intelligence
CHRP
BIND
Berkeley Internet Name
Daemon
Common Hardware
Reference Platform
© Copyright IBM Corp. 2002. All rights reserved.
319
CISPR
International Special
Committee on Radio
Interference
DHCP
Dynamic Host Configuration
Protocol
DIMM
Dual In-Line Memory Module
CLIO/S
Client Input/Output Sockets
DIP
Direct Insertion Probe
CLVM
Concurrent LVM
DIT
Directory Information Tree
CMOS
Complimentary Metal-Oxide
Semiconductor
DIVA
Digital Inquiry Voice Answer
CMP
Certificate Management
Protocol
DLT
Digital Linear Tape
DMA
Direct Memory Access
COFF
Common Object File Format
DMT
Directory Management Tool
Computer Output to Laser
Disk
DN
Distinguished Name
DNS
Domain Naming System
CPU
Central Processing Unit
DOE
Department of Energy
CRC
Cyclic Redundancy Check
DOI
Domain of Interpretation
CSID
Character Set ID
DOS
Disk Operating System
CSR
Customer Service
Representative
DPCL
Dynamic Probe Class Library
DRAM
CSS
Communication Subsystems
Support
Dynamic Random Access
Memory
DS
Differentiated Service
CSU
Customer Set-Up
DSA
Dynamic Segment Allocation
CWS
Control Workstation
DSE
Diagnostic System Exerciser
DAD
Duplicate Address Detection
DSMIT
Distributed SMIT
DAS
Dual Attach Station
DSU
Data Service Unit
DASD
Direct Access Storage Device
DTE
Data Terminating Equipment
DAT
Digital Audio Tape
DW
Data Warehouse
DBCS
Double Byte Character Set
EA
Effective Address
DBE
Double Buffer Extension
EC
Engineering Change
DC
Direct Current
ECC
DCE
Distributed Computing
Environment
Error Checking and
Correcting
EEPROM
DDC
Display Data Channel
DDS
Digital Data Storage
Electrically Erasable
Programmable Read Only
Memory
DE
Dual-Ended
EFI
Extensible Firmware Interface
DES
Data Encryption Standard
EHD
Extended Hardware Drivers
DFL
Divide Float
EIA
DFP
Dynamic Feedback Protocol
Electronic Industries
Association
DFS
Distributed File System
EISA
Extended Industry Standard
Architecture
COLD
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IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
ELA
Error Log Analysis
FRU
Field Replaceable Unit
ELF
Executable and Linking
Format
FSRM
File System Resource
Manager
EMU
European Monetary Union
FTP
File Transfer Protocol
EOF
End of File
FTP
File Transfer Protocol
EPOW
Environmental and Power
Warning
GAI
Graphic Adapter Interface
GAMESS
ERRM
Event Response resource
manager
General Atomic and
Molecular Electronic Structure
System
ESID
Effective Segment ID
GPFS
General Parallel File System
ESP
Encapsulating Security
Payload
GPR
General-Purpose Register
GUI
Graphical User Interface
ESSL
Engineering and Scientific
Subroutine Library
GUID
Globally Unique Identifier
HACMP
High Availability Cluster Multi
Processing
HACWS
High Availability Control
Workstation
HCON
IBM AIX Host Connection
Program/6000
ETML
Extract, Transformation,
Movement, and Loading
F/C
Feature Code
F/W
Fast and Wide
FC
Fibre Channel
FCAL
Fibre Channel Arbitrated Loop
HDX
Half Duplex
FCC
Federal Communication
Commission
HFT
High Function Terminal
HIPPI
High Performance Parallel
Interface
HiPS
High Performance Switch
HiPS LC-8
Low-Cost Eight-Port High
Performance Switch
HMC
Hardware Management
Console
FCP
Fibre Channel Protocol
FDDI
Fiber Distributed Data
Interface
FDPR
Feedback Directed Program
Restructuring
FDX
Full Duplex
FIFO
First In/First Out
HostRM
Host Resource Manager
FLASH EPROM
Flash Erasable
Programmable Read-Only
Memory
HP
Hewlett-Packard
HPF
High Performance FORTRAN
HPSSDL
High Performance
Supercomputer Systems
Development Laboratory
FLIH
First Level Interrupt Handler
FMA
Floating point Multiply Add
operation
HP-UX
Hewlett-Packard UNIX
FPR
Floating Point Register
HTML
Hyper-text Markup Language
FPU
Floating Point Unit
HTTP
Hypertext Transfer Protocol
FRCA
Fast Response Cache
Architecture
Hz
Hertz
Abbreviations and acronyms
321
I/O
Input/Output
IS
Integrated Service
I2 C
Inter Integrated-Circuit
Communications
ISA
IAR
Instruction Address Register
Industry Standard
Architecture, Instruction Set
Architecture
IBM
International Business
Machines
ISAKMP
Internet Security Association
Management Protocol
ICCCM
Inter-Client Communications
Conventions Manual
ISB
Intermediate Switch Board
ISDN
Integrated-Services Digital
Network
ICE
Inter-Client Exchange
ICElib
Inter-Client Exchange library
ISMP
InstallSheild Multi-Platform
ICMP
Internet Control Message
Protocol
ISNO
Interface Specific Network
Options
ID
Identification
ISO
IDE
Integrated Device Electronics
International Organization for
Standardization
IDS
Intelligent Decision Server
ISV
Independent Software Vendor
IEEE
Institute of Electrical and
Electronics Engineers
ITSO
International Technical
Support Organization
IETF
Internet Engineering Task
Force
JBOD
Just a Bunch of Disks
JDBC
Java Database Connectivity
IHV
Independent Hardware
Vendor
JFC
Java Foundation Classes
JFS
Journaled File System
IIOP
Internet Inter-ORB Protocol
JTAG
Joint Test Action Group
IJG
Independent JPEG Group
KDC
Key Distribution Center
IKE
Internet Key Exchange
L1
Level 1
ILS
International Language
Support
L2
Level 2
L2
Level 2
IM
Input Method
LAN
Local Area Network
INRIA
Institut National de Recherche
en Informatique et en
Automatique
LANE
Local Area Network
Emulation
IP
Internetwork Protocol (OSI)
LAPI
Low-Level Application
Programming Interface
IPL
Initial Program Load
LDAP
IPSec
IP Security
Lightweight Directory Access
Protocol
IrDA
Infrared Data Association
(which sets standards for
infrared support including
protocols for data
interchange)
LDIF
LDAP Directory Interchange
Format
LED
Light Emitting Diode
LFD
Load Float Double
Interrupt Request
LFT
Low Function Terminal
IRQ
322
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
LID
Load ID
MP
Multiprocessor
LLNL
Lawrence Livermore National
Laboratory
MPC-3
Multimedia PC-3
MPI
Message Passing Interface
LP
Logical Partition
MPOA
Multiprotocol over ATM
LP64
Long-Pointer 64
MPP
Massively Parallel Processing
LPI
Lines Per Inch
MPS
LPP
Licensed Program Product
Mathematical Programming
System
LPR/LPD
Line Printer/Line Printer
Daemon
MST
Machine State
MTU
Maximum Transmission Unit
LRU
Least Recently Used
MWCC
LTG
Logical Track Group
Mirror Write Consistency
Check
LV
Logical Volume
MX
Mezzanine Bus
LVCB
Logical Volume Control Block
NBC
Network Buffer Cache
LVD
Low Voltage Differential
NCP
Network Control Point
LVM
Logical Volume Manager
ND
Neighbor Discovery
MAP
Maintenance Analysis
Procedure
NDP
Neighbor Discovery Protocol
NFB
No Frame Buffer
MASS
Mathematical Acceleration
Subsystem
NFS
Network File System
MAU
Multiple Access Unit
NHRP
Next Hop Resolution Protocol
MBCS
Multi-Byte Character Support
NIM
Network Installation
Management
Mbps
Megabits Per Second
NIS
Network Information System
MBps
Megabytes Per Second
NL
National Language
MCA
Micro Channel Architecture
NLS
National Language Support
MCAD
Mechanical Computer-Aided
Design
NT-1
Network Terminator-1
NTF
No Trouble Found
NTP
Network Time Protocol
NUMA
Non-Uniform Memory Access
MDI
Media Dependent Interface
MES
Miscellaneous Equipment
Specification
MFLOPS
Million of FLoating point
Operations Per Second
NUS
Numerical Aerodynamic
Simulation
MII
Media Independent Interface
NVRAM
MIP
Mixed-Integer Programming
Non-Volatile Random Access
Memory
MLR1
Multi-Channel Linear
Recording 1
NWP
Numerical Weather Prediction
OACK
Option Acknowledgment
MMF
Multi-Mode Fibre
OCS
Online Customer Support
MODS
Memory Overlay Detection
Subsystem
ODBC
Open DataBase Connectivity
ODM
Object Data Manager
Abbreviations and acronyms
323
OEM
Original Equipment
Manufacturer
POE
Parallel Operating
Environment
OLAP
Online Analytical Processing
POP
Power-On Password
OLTP
Online Transaction
Processing
POSIX
Portable Operating Interface
for Computing Environments
ONC+
Open Network Computing
POST
Power-On Self-test
OOUI
Object-Oriented User
Interface
POWER
OSF
Open Software Foundation,
Inc.
Performance Optimization
with Enhanced Risc
(Architecture)
PPC
PowerPC
OSL
Optimization Subroutine
Library
PPM
Piecewise Parabolic Method
PPP
Point-to-Point Protocol
OSLp
Parallel Optimization
Subroutine Library
PREP
PowerPC Reference Platform
PSE
Portable Streams
Environment
P2SC
POWER2 Single/Super Chip
PAM
Pluggable Authentication
Mechanism
PSSP
Parallel System Support
Program
PAP
Privileged Access Password
PTF
Program Temporary Fix
PBLAS
Parallel Basic Linear Algebra
Subprograms
PTPE
Performance Toolbox Parallel
Extensions
PCI
Peripheral Component
Interconnect
PTX
Performance Toolbox
PV
Physical Volume
PVC
Permanent Virtual Circuit
PVID
Physical Volume Identifier
QMF
Query Management Facility
QoS
Quality of Service
PDT
Paging Device Table
PDU
Power Distribution Unit
PE
Parallel Environment
PEDB
Parallel Environment
Debugging
PEX
PHIGS Extension to X
QP
Quadratic Programming
PFS
Perfect Forward Security
RAID
PGID
Process Group ID
Redundant Array of
Independent Disks
PHB
Processor Host Bridges
RAM
Random Access Memory
PHY
Physical Layer
RAN
Remote Asynchronous Node
PID
Process ID
RAS
Reliability, Availability, and
Serviceability
PID
Process ID
RDB
Relational DataBase
PIOFS
Parallel Input Output File
System
RDBMS
Relational Database
Management System
PKR
Protection Key Registers
RDISC
ICMP Router Discovery
PMTU
Path MTU
RDN
Relative Distinguished Name
324
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
RDP
Router Discovery Protocol
RFC
Request for Comments
SDLC
Synchronous Data Link
Control
RIO
Remote I/O
SDR
System Data Repository
RIP
Routing Information Protocol
SDRAM
RIPL
Remote Initial Program Load
Synchronous Dynamic
Random Access Memory
RISC
Reduced Instruction-Set
Computer
SE
Single Ended
SEPBU
RMC
Resource Monitoring and
Control
Scalable Electrical Power
Base Unit
SGI
Silicon Graphics Incorporated
SGID
Set Group ID
SHLAP
Shared Library Assistant
Process
ROLTP
Relative Online Transaction
Processing
RPA
RS/6000 Platform
Architecture
SID
Segment ID
RPC
Remote Procedure Call
SIT
Simple Internet Transition
RPL
Remote Program Loader
SKIP
RPM
Redhat Package Manager
Simple Key Management for
IP
RSC
RISC Single Chip
SLB
Segment Lookaside Buffer
RSCT
Reliable Scalable Cluster
Technology
SLIH
Second Level Interrupt
Handler
RSE
Register Stack Engine
SLIP
Serial Line Internet Protocol
RSVP
Resource Reservation
Protocol
SLR1
Single-Channel Linear
Recording 1
RTC
Real-Time Clock
SM
Session Management
RVSD
Recoverable Virtual Shared
Disk
SMB
Server Message Block
SMIT
SA
Secure Association
System Management
Interface Tool
SACK
Selective Acknowledgments
SMP
Symmetric Multiprocessor
SAN
Storage Area Network
SMS
SAR
Solutions Assurance Review
System Management
Services
SAS
Single Attach Station
SNG
Secured Network Gateway
SBCS
Single-Byte Character
Support
SOI
Silicon-on-Insulator
SP
ScaLAPACK
Scalable Linear Algebra
Package
IBM RS/6000 Scalable
POWER parallel Systems
SP
Service Processor
SCB
Segment Control Block
SPCN
SCSI
Small Computer System
Interface
System Power Control
Network
SPEC
SCSI-SE
SCSI-Single Ended
System Performance
Evaluation Cooperative
SPI
Security Parameter Index
Abbreviations and acronyms
325
System Performance
Measurement
UDI
Uniform Device Interface
UIL
User Interface Language
SPOT
Shared Product Object Tree
ULS
Universal Language Support
SPS
SP Switch
UP
Uniprocessor
SPS-8
Eight-Port SP Switch
USB
Universal Serial Bus
SRC
System Resource Controller
USLA
User-Space Loader Assistant
SRN
Service Request Number
UTF
UCS Transformation Format
SSA
Serial Storage Architecture
UTM
Uniform Transfer Model
SSC
System Support Controller
UTP
Unshielded Twisted Pair
SSL
Secure Socket Layer
UUCP
STFDU
Store Float Double with
Update
UNIX-to-UNIX
Communication Protocol
VESA
STP
Shielded Twisted Pair
Video Electronics Standards
Association
SUID
Set User ID
VFB
Virtual Frame Buffer
SUP
Software Update Protocol
VG
Volume Group
SVC
Switch Virtual Circuit
VGDA
SVC
Supervisor or System Call
Volume Group Descriptor
Area
SWVPD
Software Vital Product Data
VGSA
Volume Group Status Area
SYNC
Synchronization
VHDCI
TCE
Translate Control Entry
Very High Density Cable
Interconnect
Tcl
Tool Command Language
VLAN
Virtual Local Area Network
TCP/IP
Transmission Control
Protocol/Internet Protocol
VMM
Virtual Memory Manager
VP
Virtual Processor
TCQ
Tagged Command Queuing
VPD
Vital Product Data
TGT
Ticket Granting Ticket
VPN
Virtual Private Network
TLB
Translation Lookaside Buffer
VSD
Virtual Shared Disk
TOS
Type Of Service
VSM
Visual System Manager
TPC
Transaction Processing
Council
VSS
Versatile Storage Server
VT
Visualization Tool
TPP
Toward Peak Performance
WAN
Wide Area Network
TSE
Text Search Engine
WLM
Workload Manager
TSE
Text Search Engine
WTE
Web Traffic Express
TTL
Time To Live
XCOFF
UCS
Universal Coded Character
Set
Extended Common Object
File Format
XIE
X Image Extension
XIM
X Input Method
XKB
X Keyboard Extension
SPM
UDB EEE
326
Universal Database and
Enterprise Extended Edition
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
XLF
XL Fortran
XOM
X Output Method
XPM
X Pixmap
XSSO
Open Single Sign-on Service
XTF
Extended Distance Feature
XVFB
X Virtual Frame Buffer
Abbreviations and acronyms
327
328
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Related publications
The publications listed in this section are considered particularly suitable for a
more detailed discussion of the topics covered in this redbook.
IBM Redbooks
For information on ordering these publications, see “How to get IBM Redbooks”
on page 331.
 AIX 5L Differences Guide, SG24-5765
 AIX 5L Performance Tools Handbook, SG24-6039
 AIX 5L Workload Manager (WLM), SG24-5977
 AIX Logical Volume Manager From A to Z: Introduction and Concepts,
SG24-5432
 IBM ^ Certification Study Guide - AIX Communications,
SG24-6186
 IBM ^ Certification Study Guide - AIX Installation and
System Recovery, SG24-6183
 IBM ^ Certification Study Guide - AIX Problem
Determination Tools and Techniques, SG24-6185
 IBM ^ Certification Study Guide - pSeries AIX System
Administration, SG24-6191
 IBM ^ Certification Study Guide - pSeries AIX System
Support, SG24-6199
 IBM ^ Certification Study Guide - pSeries HACMP for AIX,
SG24-6187
 IBM ^ Certification Study Guide - RS/6000 SP, SG24-5348
 Managing AIX Server Farms, SG24-6606
 Problem Solving and Troubleshooting in AIX 5L, SG24-5496
 RS/6000 Performance Tools in Focus, SG24-4989
 TCP/IP Tutorial and Technical Overview, GG24-3376
© Copyright IBM Corp. 2002. All rights reserved.
329
Other resources
These publications are also relevant as further information sources:
 AIX Version 4 System Management Guide: Operating System and Devices,
SC23-2525
 AIX Version 4.3 System Management Concepts: Operating System and
Devices, SC23-4311
 RS/6000 and pSeries PCI Adapter Placement Reference, SA38-0538
 SSA Adapters: User’s Guide and Maintenance Information, SA33-3272
 The following types of documentation are located through the Internet at the
following URL:
http://www-1.ibm.com/servers/eserver/pseries/library
– User guides
– System management guides
– Application programmer guides
– All commands reference volumes
– Files reference
– Technical reference volumes used by application programmers
Referenced Web sites
These Web sites are also relevant as further information sources:
 IBM certification tests information
http://www.ibm.com/certify/tests/info.shtml
 IBM eServer pSeries support
http://techsupport.services.ibm.com/server/support?view=pSeries
 IBM hardware documentation
http://www.ibm.com/servers/eserver/pseries/library/hardware_docs/index.html
 IBM Professional Certification Program
http://www.ibm.com/certify
 IBM TotalStorage
http://www.storage.ibm.com
330
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
 Open Group Technical Standard, Protocols for Interworking XNFS Version
3W
http://www.opengroup.org/onlinepubs/9629799/toc.htm
 perfpmr installation readme file
ftp://ftp.software.ibm.com/aix/tools/perftools/perfpmr/perf51/
 UNIX servers (pSeries) information
http://www-132.ibm.com/content/home/store_IBMPublicUSA/en_US/eServer/pSerie
s/pSeries.html
How to get IBM Redbooks
You can order hardcopy Redbooks, as well as view, download, or search for
Redbooks at the following Web site:
ibm.com/redbooks
You can also download additional materials (code samples or diskette/CD-ROM
images) from that site.
IBM Redbooks collections
Redbooks are also available on CD-ROMs. Click the CD-ROMs button on the
Redbooks Web site for information about all the CD-ROMs offered, as well as
updates and formats.
Related publications
331
332
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Index
Symbols
(SLA) 34
/etc/hosts 194–195
/etc/netsvc.conf 194
/etc/rc.nfs 197
/etc/resolv.conf 194
/proc
see also proc pseudo file system 103
__prof.all 67
Numerics
32bit, WLM process type 240
64bit
WLM process type 240
automatic reboot 124
availability
logical volume manager 134
B
bad block policy 133
base value 210
batch 252
BB policy 133
bigfile file system 151
BIND / DNS 194
bindprocessor 221
bos.perf fileset 305
bosboot 129
bottleneck 125
SCSI adapter 128
A
adapter
SCSI bottleneck 128
administration
workload manager 230
AIX tools
By system resource 303
Full path name 300
Monitoring tools 303
See also Commands
allocation
logical volume 139
allocation policy
intra disk 134
Application 303
application path names (WLM) 240
application performance 157
application tags (WLM) 240
as pseudo file 105
assignment rules (WLM) 237
at 252
atmstat 187
attributes
classes 234
logical volume 132
attributes, localshm 236
automatic assignment (WLM) 236
© Copyright IBM Corp. 2002. All rights reserved.
C
center disk allocation 134
chdev 175, 177, 193
chnfs 196, 198
class
inheritance 235
class assignment rules 239
class name (WLM) 239
classes 229
classification process 236
collecting
disk I/O history 120
collecting data
sar command 40
svmon 70
commads
netpmon 32
nice 220
commands 177
/etc/netsvc.conf 194
/etc/resolv.conf 194
at 252
batch 252
chdev 175, 177, 193
chnfs 196, 198
defragfs 160
333
emstat 102
entstat 175–176
filemon 28, 141, 164
fileplace 29, 157, 164
host 194
ifconfig 175, 193
installp 310
iostat 27, 118, 250
iptrace 190
lockstat 129
lsattr 175, 193
lsdev 271
lslpp 103, 311
lslv 29, 131, 165
lsps 22, 126, 271
lsrset 243
migratepv 263
mkclass 236
netpmon 188
netstat 31, 95, 175, 180
nfso 177, 196
nfsstat 31
nice 15, 218
no 173, 181
nslookup 194
od 107
ping 179
ps 14, 22, 61, 209, 251, 264
renice 15, 218, 220
reorgvg 260
rmss 23
rmss, rmss command 73
sa1 52
sa2 52
sadc 51
sar 12, 40, 44, 95
schedtune 15, 214
svmon 22, 70–71, 73, 77, 80, 83, 85, 266
tcpdump 177, 190
time 13, 250
tokstat 175
topas 95
command output 100
tprof 14, 67
traceroute 180
trcstop 188
vmstat 13, 20, 53, 95, 103, 179, 251, 264
vmtune 22, 27, 59, 222, 271
wlmcntrl 246
334
compatibility
workload manager 242
computational memory 19
copies
logical volume 132
CPU
bound problem 126
iostat utilization report 125
statistics with iostat 125
CPU bound 9
process and thread table 12
process state figure 11
processes 10
threads 10
CPU penalty 210
CPU testcase 250
at 252
batch 252
iostat 250
ps 251
recent CPU usage 252
rescheduling 252
time 250
vmstat 251
cred pseudo file 105
crfs 152
crontab 252
ctl pseudo file 105
D
Data fragmentation 155
DEFAULT_NICE 210
deferred page space allocation 20
defragfs command 160
de-fragmentation of file system 160
detailed file stats report in filemon 145
disk
I/O statistics with iostat 118
I/O wait 179
iostat utilization report 127
unbalanced load 126
disk bound 23
logical volume device driver 23
logical volume manager 23
lvdd figure 24
disk bound problem 126
disk bound problems 149
disk I/O pacing 121
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Disk-I/O pacing 121
distribution column in lslv -l 138
DPSA 20
E
early alloaction algorithm 20
emstat 102
emulation routines 102
Enhanced Journaled File System (JFS2) 152
entstat 175, 183
entstat command 176
errclear 290
exec() system call 237, 241
Extents 155
F
fddistat 184
figures
128 run queues 209
code, data.private and shared segments 17
CPU penalty 216
Disk, LVM and file system levels 118
global run queue 208
JFS file system organization 151
lvdd 24
LVM figure 25
LVM intra disk positions 135
memory registers 18
muliple run queues 212
network parameters 30
performance tuning flowchart 10
process state 11
VMM segments 16
file memory 19
file system
bigfile file system 151
de-fragmentation 160
fileplace command 157
fragmentation size 150
i-node 150
journaled file system - JFS 150
logical fragment 159
organization 150
performance 150
recommendations 162
filemon 28
command 141, 164
detailed file stats report 145
disk access 149
frequently accessed files 149
logical file system 141
logical volume monitoring 142
monitoring scenario 260
most active files report 145
physical volume monitoring 142
report
logical file level 143
logical volume level report 146
physical volume level 147
virtual memory level 148
report analysis 143
virtual memory system monitoring 142
fileplace 29
fileplace command 157, 164
files
/etc/hosts 194
/etc/rc.nfs 197
/usr/include/sys/lockname.h 131
__prof.all 67
crontab 12
filesets
bos.perf 305
fixed 240
fork 237
fragmentation
fileplace command 158
logical volume fragmentation scenario 259
fragmentation of logical volume 138
fragmentation size 150
fragmented files 158
free list 18
frequent periodic load balancing 213
frequently accessed files 149
G
global run queue 207
group (WLM) 240
H
hash anchor table 19
high- and low-water marks 121
high-water mark 27
historical disk I/O 120
Historical-record retention period for PDT reports
34
host 194
Index
335
I
I/O bottlenecks
scenarios 256
I/O pacing 27
idle load balancing 213
ifconfig 175, 193
in band column in lslv -l 138
infrequent periodic load balancing 214
initial load balancing 213
inner edge disk allocation 134
inner middle disk allocation 134
i-node 150
installp 310
instfix 308
inter disk policy 135
for logical volume 132
maximum 135
minimum 135
internal fragmentation 155
intra disk
allocation 134
policy
center 134
inner edge 134
inner middle 134
outer edge 134
outer middle 134
policy for logical volume 132
iostat 27, 95, 250
enhancement to 4.3.3 28
iostat command 118
historical disk I/O 120
SMP behaviour 126
IP 172
data flow 174
input queue 178, 183
ipforwarding 178
ipqmaxlen 178, 183
iptrace 177, 190
J
JFS 25
bigfile file system 151
file system organization 150
fileplace command 157
fragmentation 25
fragmentation size 150
i-node 150
336
performance tools 117
JFS log 156
Journeled filesystems log 156
K
kernel locks
display with lockstat 129
L
late allocation algorithm 19
limitations
striping 162
List of files monitored by PDT 34
load balancing 213
frequent periodic load balancing 213
idle load balancing 213
infrequent periodic load balancing 214
initial load balancing 213
lock
display of lock contention with lockstat 129
lock contention
display with lockstat 129
lockstat command 129
logical fragment 159
logical partition 24
logical volume 24
allocation 139
allocation scenario 260
attributes 132
bad block policy 133
copies 132
distribution 138
fragmentation 138
fragmentation scenario 259
highest performance 141
inter disk policy 132, 135
intra disk policy 132
mirror write consistency 132
organization for highest performance 160
relocateable 133
scheduling policy 133
stripe size 136
stripe width 136
striping 136, 161
upper bound 133
write policy
parallel 133
parallel/round robin 133
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
parallel/sequential 133
sequential 134
write verify 133
logical volume device dirver 23
logical volume manager
availability 134
monitoring 141
performance
analysis with lslv 131
tools 117
logical volume manger 23
low-water mark 27
lsattr 175, 193
lsdev command 271
lsfs 152
lslpp 103, 311
lslv 29
lslv command 131, 165
lsps 22
lsps -a command 126
lsps command 271
lsrset command 243
LVDD 23
LVM 23
dependecies figure 25
fragmentation 25
high-water mark 27
I/O pacing 27
JFS 25
logical partition 24
logical volume 24
low-water mark 27
maxpgahead 26
minpgahead 26
physical partition 24
physical volume 24
sequential-access read ahead 26
volume group 24
write-behind 26
lwp pseudo file directory 106
lwpctl pseudo file 107
lwpsinfo pseudo file 107
lwpstatus pseudo file 107
M
manual assignment (WLM) 237
map pseudo file 105
maximum transfer unit (MTU) 172
maxpgahead 26
mbufs 177, 182
memory bound 15
virtual memory 15
migratepv 156
migratepv command 263
minpgahead 26
mirror write consistency 132
Mirroring 133
mkclass command 236
mkfs 152
Modifying the list of hosts monitored by PDT 34
monitoring
filemon command 141
logical volume 141
scenario with filemon 260
Monitoring tools 303
most active files report 145
MTU 193
MTU discovery algorithm 178
MTU discovery for TCP 178
MTU discovery for UDP 178
multiple run queues 211
multiprocessor
behaviour of iostat 126
N
name resolution
performance 194
netpmon 32, 188
netstat 31, 95, 175, 180, 183, 185–186
netstat -r 178
network
I/O wait 179
tuning tools 192
network bound 29
parameter figure 30
NFS 189
client performance 197
file system 198
mount options 198
server performance 195
tuning 195
nfs 196
nfso 177
nfso command 196
nfsstat 31
NICE 210
Index
337
nice 15, 210, 218–220
changing value on running thread 220
flag table 220
running program with nice 219
NIS 194
no 173, 178, 181
nointegrity 157
nslookup 194
NSORDER 194
O
object pseudo file directory 106
od command 107
organization
file system 150
oslevel 308
outer edge disk allocation 134
outer middle disk allocation 134
overhead
of performing tools 163
P
packet
dropped 177, 182
page fault 18
page frame table 18
page stealing 18
paging performance problem 263
investigation 271
recommendations 274
paging space
disk performance 163
parallel write policy 133
parallel/round robin write policy 133
parallel/sequential write policy 133
Path names for AIX tools 300
PDT 33
PDT collection, retention and reporting times 34
PDT error reporting 34
PDT report on demand 34
PDT report recipient 34
PDT security leve 34
PDT thresholds 34
performace
filemon 141
performance
analysis and control 299
controlling resource allocation 9
338
CPU bound 9
define and prioritizie 8
disk bound 23
file system 150
file system recommendations 162
highest logical volume performance 141
identify resources 8
identify workload 8
load monitoring 299
logical volume manager
analysis with lslv 131
lvdd 24
LVM and JFS performance tools 117
LVM dependencies figure 25
memory bound 15
memory register figure 18
minimize requirements 9
network bound 29
network parameter figure 30
process and thread table 12
process state figure 11
processes 10
resource table 8
threads 10
tuning flowchart picture 10
VMM segment figure 16
VMM segment picture 17
vmstat table 21
performance capacity planning 299
Performance PMR Data Collection 305
performance tools 299
fileset
perfagent.server 306
perfagent.tool 306
perfmgr.common 306
perfmgr.local 306
perfmgr.network 306
installing 299
Performance Toolbox 306
releases 306
Performance Toolbox Agent 306
Performance Toolbox Manager 306, 310
physical partition 24
physical volume 24
filemon report 147
unbalanced load 126
physical volume utilization 128
ping 179
plock 240
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
plock() system call 241
priority 210
priority calculation 4.3.2 207
priority calculation 4.3.3 210
problems
disk bound 149
proc pseudo file system
as pseudo file 105
cred pseudo file 105
ctl pseudo file 105
lwp pseudo file directory 106
lwpctl pseudo file 107
lwpsinfo pseudo file 107
lwpstatus pseudo file 107
map pseudo file 105
object pseudo file directory 106
psinfo pseudo file 105
sigact pseudo file 105
status pseudo file 105
sysent pseudo file 105
vfs entry 104
process type (WLM) 240
processes 10
processor
601 PowerPC 102
604 PowerPC 102
POWER 102
instructions 102
PowerPC 102
prof
total collumn 68
protocol
statistics 180
protocols
IP 172
TCP 172
tuning 176
UDP 172
ps 14, 22, 61, 209, 251
%CPU column 63
%MEM column 66
C column 62
PGIN column 66
RSS column 65
SIZE column 65
TIME column 63
TRS column 67
TSIZ column 67
ps command 264
PSALLOC 19
Deferred Page Space Allocation 20
early allocation algorithm 20
late allocation algorithm 19
pseudo file directories 106
pseudo files 105, 107
psinfo pseudo file 105
Q
queue
receive 174
size 175
transmit 174
R
reachable 194
receive queue 172
recent CPU usage 209
Redbooks Web site 331
Contact us xviii
registers 17
relocatable
attribute for logical volume 133
renice 15, 218, 220
flag table 221
reorgvg command 260
report
iostat 120
CPU utilization 125
disk utilization 127
TTY utilization 125
rescheduling 252
resent CPU usage 252
resource sets (WLM) 243
rfc1323 178
rmss 23
rset 244
rset registry 244
rx_que_size 172
S
sa1 command 52
sa2 command 52
sadc command 51
sar 12, 40, 95
/usr/lib/sa/sa1 12
usr/lib/sa/sa2 12
Index
339
sar command 40, 44
flags 45
saturated SCSI adapter 129
sb_max 178
scenarios
filemon monitoring 260
I/O bottlenecks 256
iostat 257
logical volume allocation 260
logical volume fragmentation 259
SCHED_D 210, 214
SCHED_FIFO 206
SCHED_FIFO2 207
SCHED_FIFO3 207
SCHED_OTHER 206
SCHED_R 210, 214
SCHED_RR 206
schedtune 15, 214
commands
schedtune 218
example 1 215
example 2 215
example 3 215
flag table
tables
schedtune flags 218
SCHED_D 214
SCHED_R 214
SCHED_R and SCHED_D guidelines 216
scheduler
128 run queue figure 209
base value 210
CPU penalty 210
CPU penalty figure 216
DEFAULT_NICE 210
global run queue 207
global run queue figure 208
load balancing 213
multiple run queue figure 212
multiple run queues 211
NICE 210
nice value 210
priority 210
priority calculation 4.3.2 207
priority calculation 4.3.3 210
recent CPU usage 209
SCHED_D 210, 214
SCHED_FIFO 206
SCHED_FIFO2 207
340
SCHED_FIFO3 207
SCHED_OTHER 206
SCHED_R 210, 214
SCHED_R and SCHED_D guidelines 216
SCHED_RR 206
schedtune example 1 215
schedtune example 2 215
schedtune example 3 215
steal threshold 213
steal_max 213
waitproc 213
xnice 210
scheduling policy for logial volume 133
SCSI
adapter bottleneck 128
segment registers 17
sequential write policy 134
sequential-access read ahead 26
Service level agreement 34
setgid() system call 241
setpri() system calls 241
setuid() system call 241
sigact pseudo file 105
slowest average seek 135
SMIT fast path
smit chgsys 120
smitty
install_all 310
list_software 309
smitty chgsys 122, 124
SMP
iostat behaviour 126
socket
active 180
buffer 195
buffer overflows 196
receive buffer 173, 177
send buffe 177
send buffer 172
Solaris affinity 107
Solaris tools 107
statfs 152
statistics
CPU 188
disk I/O 118
Internet socket calls 189
mbufs 182
network device-driver I/O 189
terminal I/O 118
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
statisticsprotocols 180
statistisc
Ethernet 175
status pseudo file 105
steal threshold 213
steal_max 213
stripe size logical volume attribute 136
stripe width logical volume attribute 136
striping 136
limitations 162
logical volume striping 161
subclass 230
superclass 230
svmon 22
svmon command 70–71, 73, 77, 80, 83, 85, 266
command report 85
output description 87
syntax 85
detailed segment report 83
output description 85
syntax 83
flags 90
global report 71
output description 72
syntax 71
process report 77
output description 80
syntax 77
report types 70
segment report 80
output description 81
syntax 80
user report 73
output description 76
syntax 73
workload class report 88
output description 89
syntax 88
sysent pseudo file 105
system
typical AIX system behaviour 149
system calls
exec() 237, 241
plock() 241
setgid() 241
setpri() 241
setuid() 241
System resources 303
T
tables
hardware and logical resources 8
nice flags 220
processes and threads 12
renice flags 221
VMM related output from vmstat 21
TCP 172, 195
data flow 174
tcp_pmtu_discover 178
tcp_recvspace 177
tcp_sendspace 172, 177
tcpdump 177, 190
telnet
session 190
terminal
I/O statistics with iostat 118
I/O wait 179
testcase
CPU 250
The performance diagnostic tool (PDT) 33
thewall 177, 182, 193
threads 10
R state 11
ready to run 11
S state 11
sleeping 11
state 10
suspended 11
T state 11
throughput
SCSI adapters 128
time 13, 250
tokstat 175
tools
LVM and JFS performance tools 117
topas 95
command output 100
tprof 14, 67
FREQ collumn 69
general report 67
using tprof on a program 69
traceroute 180
traceroute command 180
translation lookaside buffer 18
transmit queue 172
trcstop 188
TTY
devices 125
Index
341
iostat utilization report 125
tx_que_size 172, 176
U
UDP 172, 195
data flow 174
udp_pmtu_discover 178
udp_recvspace 177
udp_sendspace 172, 177
unbalanced disk load 126
Uninstalling PDT 34
upper bound attribute for logical volume 133
user (WLM) 239
usr/sbin/perf/diag_tool/pdt_config 33
utilization
CPU with iostat 125
disk with iostat 127
TTY with iostat 125
V
virtual memory
client segment 16
code segment 17
computational memory 19
data segment 17
file memory 19
filemon report 148
free list 18
HAT 19
high-water mark 27
I/O pacing 27
low-water mark 27
maxpgahead 26
memory register figure 18
minpgahead 26
page fault 18
page stealing 18
persistent segment 16
private segment 17
PSALLOC 19
PTF 18
segment figure 16
segment picture 17
segment registers 17
segments 15
sequential-access read ahead 26
shared segment 17
TLB 18
342
vmstat table 21
working segment 16
write-behind 26
Virtual Memory Manager (VMM) 222–223
virtual memory monitoring
filemon command 141
vmstat 13, 20, 95, 103, 179, 251
vmstat command 53, 264
cpu column description 273
faults column description 273
kthr column description 272
memory column description 272
output description 54
output interpretation 60
page column description 272
sum structure 56
vmtune 22, 27, 222
vmtune command 59, 222, 271
flags 224
syntax 222
volume group 24
W
waitproc 213
wirte-behind 26
WLM
32bit 240
64bit 240
fixed 240
plock 240
wlm, localshm 236
wlm, shared memory segment 235
wlmcntrl command 246
workload
identify 8
Workload Manager
class attributes 234
classes 229
inheritance 235
subclass 230
superclass 230
write policy
parallel 133
parallel/round robin 133
parallel/sequential 133
sequential 134
write verify for logical volume 133
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
X
xnice 210
Index
343
344
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
IBM ^ Certification Study Guide - AIX 5L Performance and System Tuning
Back cover
®
IBM
Certification Study Guide AIX 5L Performance and
System Tuning
Developed
specifically for the
purpose of preparing
for AIX certification
Makes an excellent
companion to
classroom education
For experienced AIX
professionals
This IBM Redbook is designed as a study guide for
professionals wishing to prepare for the AIX 5L Performance
and System Tuning certification exam as a selected course of
study in order to achieve the IBM ^ Certified
Advanced Technical Expert - pSeries and AIX 5L certification.
INTERNATIONAL
TECHNICAL
SUPPORT
ORGANIZATION
This IBM Redbook is designed to provide a combination of
theory and practical experience needed for a general
understanding of the subject matter. It also provides sample
questions that will help with the evaluation of personal
progress and provide familiarity with the types of questions
that will be encountered on the exam.
BUILDING TECHNICAL
INFORMATION BASED ON
PRACTICAL EXPERIENCE
This publication does not replace practical experience, nor is
it designed to be a stand-alone guide for any subject. Instead,
it is an effective tool that, when combined with education
activities and experience, can be a very useful preparation
guide for the exam. Whether you are planning to take the AIX
5L Performance and System Tuning certification exam, or if
you just want to validate your AIX skills, this redbook is for
you.
IBM Redbooks are developed by
the IBM International Technical
Support Organization. Experts
from IBM, Customers and
Partners from around the world
create timely technical
information based on realistic
scenarios. Specific
recommendations are provided
to help you implement IT
solutions more effectively in
your environment.
This publication was updated to include the new content
included in Test 234, which is based on AIX 5L Version 5.1.
For more information:
ibm.com/redbooks
SG24-6184-01
ISBN 0738427012