Linux 操作系统 系统优化

1. Linux操作系统系统优化 周炯 上海艾基信息技术有限公司 Acegene IT Co. Ltd.

2. 内容提要 • Performance concepts and measurement tools: • CPU • Memory • Disk I/O • Network • Process • Profiling Kernel & Applications Acegene IT Co. Ltd.

3. Measurement Tools • Linux has measurement tools common toUNIX platforms: • System Activity Reporter: sar • Historical database • Virtual Memory Statistics: vmstat, free • I/O Statistics: iostat • Top Resource Consumers: top -c • X-based tools: xosview, gnome-system-monitor, ksysguard, gkrellm

4. CPU Measurements • Identify the CPU statistics and interpret them: • Idle time: %idle • Executing user code: %user • Executing system code: %system • Load average: runq-sz • Start with cat /proc/cpuinfo • Total CPU count/speed • There are several ways to see the same information, for example: CPU activity

5. CPU Activity - mpstat • What is my CPU doing?: mpstat # mpstat -P <cpu> <interval> <count> # mpstat -P ALL 1 1 Linux 2.4.21-15.EL (raclinux1) 08/04/2004 CPU %user %nice %system %idle intr/s all 19.50 0.00 31.50 49.00 111.00 0 27.00 0.00 42.00 31.00 111.00 1 12.00 0.00 21.00 67.00 111.00

6. CPU Activity - sar • What is my CPU doing?: sar # sar -u <interval> <count> # sar -u 2 3 Linux 2.4.21-15.EL (raclinux1) 08/04/2004 02:02:34 AM CPU %user %nice %system %idle 02:02:36 AM all 1.14 0.00 1.71 97.14 02:02:38 AM all 2.62 0.00 3.66 93.72 02:02:40 AM all 0.54 0.00 3.78 95.68 Average: all 1.45 0.00 3.09 95.46

7. CPU Activity - iostat • What is my CPU doing?: iostat # iostat -c <interval> <count> # iostat -c 2 3 Linux 2.4.21-15.EL (raclinux1) 08/04/2004 avg-cpu: %user %nice %sys %idle 5.73 0.00 17.16 77.11 avg-cpu: %user %nice %sys %idle 4.62 0.00 27.18 68.21 avg-cpu: %user %nice %sys %idle 9.55 0.00 35.96 54.49

8. Linux Virtual Memory • Each process is assigned a contiguous address space in virtual memory that maps process memory allocations to the real memory • User address space is a contiguous set of pages and is limited to 4GB per process • Physical Address Extension (PAE), allows access to more than 4GB of physical memory • RHat: ‘enterprise’ kernel (implied SMP) • SuSE: 64GB kernel (implied SMP)

9. Swap Swapped-in pages Physical memory (RAM) Swapped-out pages Virtual memory Swap space (disk)

10. Measuring Swap • How much is available/used? • swapon -s (cat /proc/swaps) • vmstat • so:Amount of memory KB/s SWAP OUT to disk • si: Amount of memory KB/s SWAP IN from disk • swapd: Amount of virtual memory KB reserved • Create/Add more? • # mkswap /dev/sdc3 • fstab:/dev/sdc3 swap swap pri=42 0 0

11. Memory Usage Buffer cache Dynamically adjusted Page cache Process memory Process memory Paged Process memory Paged/locked Shared memory Kernel modules Not paged Kernel (not paged)

12. Page in Page out Measuring Memory Usage • Measure memory utilization and paging. Identify the significant memory statistics. • cat /proc/meminfo (units KB) • MemTotal: Total physical memory • MemFree: Total free memory • LowFree: Free memory below 1GB physical • Buffers: Linux Buffer Cache • Cached: Linux Page Cache • BigFree: Free bigpages memory

13. No Free Memory? • freecommand reports a very low number, should I be worried • It’s OK if Linux buffer or page cache are big • Look in -/+ buffer/cache row of free for projected free memory • Very useful stat

14. Memory - sar • -B paging statistics • -R memory statistics • -W swapping statistics #sar -B <frequency> <count> #sar -R <frequency> <count>

15. Measuring Disk I/O • You should monitor the I/O across all devices and look for ‘slow’ devices using: • sar, iostat, vmstat • Archive collected statistics for comparison Acegene IT Co. Ltd.

16. Network Traffic • Check the following sources of network traffic: • Oracle SQL*Net Servicing SQL connections • Interconnect in RAC environment • Network file system • Samba • HTTP server • Start with sar -n DEV • iptraf also very useful Acegene IT Co. Ltd.

17. sar Flags • -f read from sar historical file • /var/log/sa/… • -s -e start/end times • -s hh:mm:ss • -r memory/swap utilization • -c process creation activity • -w context switching activity

18. Process Specific • Specific process is a suspect: • System call trace: • strace –p <pid> • Library call trace: • ltrace –p <pid> • Detailed process statistics: • ps –o <options> • Try: ps -e -o pid,ppid,pcpu,rss,vsz,pri,wchan,cmd • Who has my file open? • lsof [-p <pid] • For Process Tree, use pstree –p • Not seeing a process, it’s probably a thread, try: ps -efm Acegene IT Co. Ltd.

19. What Does the Kernel Do? • It’s possible to profile the kernel and identify where it’s spending time: • Boot with “profile=2 nmi_watchdog=1” • Either in Lilo or Grub or add manually at boottime • Use readprofile -m <map> • Start with readprofile -r (to reset counters) • Very easy to use, but useful only if you see high system time. • To profile user applications use oprofile • http://oprofile.sourceforge.net/ Acegene IT Co. Ltd.

20. System Wide • RDA (Remote Diagnostic Agent) • http://set.oraclecorp.com/tools/dca/index.html • Lshw (Hardware Lister) • http://freshmeat.net/projects/lshw/ Acegene IT Co. Ltd.

21. Summary: Linux Monitoring Tools • Overall tools • sar , vmstat • CPU • /proc/cpuinfo , mpstat , top • Memory • /proc/meminfo , /proc/slabinfo • Disk I/O • iostat, sar • Network • iptraf, netstat, mii-tool • Individual process debugging • strace , ltrace, lsof Acegene IT Co. Ltd.

22. Q & Q U E S T I O N S A N S W E R S A

23. 练习 • 执行下列命令 • sar , vmstat • /proc/cpuinfo , mpstat , top • /proc/meminfo , /proc/slabinfo • iostat, sar • iptraf, netstat, mii-tool • strace , ltrace, lsof Acegene IT Co. Ltd.