Front cover Tuning Red Hat Enterprise Linux on IBM Eserver xSeries Servers Describes ways to tune the operating system Introduces performance tuning tools Covers key server applications Eduardo Ciliendo ibm.com/redbooks Redpaper International Technical Support Organization Tuning Red Hat Enterprise Linux on IBM Eserver xSeries Servers July 2005 Note: Before using this information and the product it supports, read the information in “Notices” on page vii. Second Edition (July 2005) This edition applies to Red Hat Enterprise Linux AS running on IBM Eserver xSeries servers. © Copyright International Business Machines Corporation 2005. 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 Notices . vii Trademarks . viii Preface . ix How this Redpaper is structured . ix The team that wrote this Redpaper . .x Become a published author . xi Comments welcome. xi Chapter 1. Understanding Linux performance . 1 1.1 The Linux CPU scheduler . 3 1.2 The Linux memory architecture. 4 1.3 The virtual memory manager . 5 1.4 Modular I/O elevators . 6 1.4.1 Anticipatory . 7 1.4.2 Complete Fair Queuing (CFQ) . 7 1.4.3 Deadline . 7 1.4.4 NOOP . 7 1.5 The network subsystem . 7 1.5.1 TCP/IP transfer window . 8 1.6 Linux file systems . 9 1.6.1 ext2 . 9 1.6.2 ext3, the default Red Hat file system . 9 1.6.3 ReiserFS . 9 1.6.4 JFS . 10 1.6.5 XFS . 10 1.7 The proc file system . 10 1.8 Understanding Linux performance metrics . 12 1.8.1 Processor metrics . 12 1.8.2 Memory metrics. 13 1.8.3 Network interface metrics . 13 1.8.4 Block device metrics . 14 Chapter 2. Monitoring tools . 15 2.1 Overview of tool function. 16 2.2 uptime . 16 2.3 dmesg . 17 2.4 top . 18 2.4.1 Process priority and nice levels. 19 2.4.2 Zombie processes. 19 2.5 iostat . 20 2.6 vmstat . 21 2.7 ps and pstree . 22 2.8 numastat . 22 2.9 sar . 23 2.10 KDE System Guard. 24 2.10.1 Work space . 25 2.11 Gnome System Monitor . 28 2.12 free . 28 © Copyright IBM Corp. 2005. All rights reserved. iii 2.13 pmap . 29 2.14 strace . 29 2.15 ulimit . 30 2.16 mpstat . 31 2.17 Capacity Manager . 32 Chapter 3. Tuning the operating system. 35 3.1 Change management . 36 3.2 Installation . 36 3.3 Daemons. 38 3.4 Changing run levels . 40 3.5 Limiting local terminals . 42 3.6 SELinux. 42 3.7 Compiling the kernel . 43 3.8 Changing kernel parameters. 44 3.8.1 Where the parameters are stored . 45 3.8.2 Using the sysctl command . ..