Linux 操作系统系统优化

Acegene IT Co. Ltd. 1

Linux 操作系统系统优化

周炯周炯上海艾基信息技术有限公司上海艾基信息技术有限公司


内容提要• Performance concepts and

measurement tools:– CPU– Memory– Disk I/O– Network– Process– Profiling Kernel & Applications

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

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

CPU Activity - mpstat

# mpstat -P <cpu> <interval> <count>

# mpstat -P ALL 1 1Linux 2.4.21-15.EL (raclinux1) 08/04/2004CPU %user %nice %system %idle intr/sall 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

• What is my CPU doing?: mpstat

CPU Activity - sar

# sar -u 2 3Linux 2.4.21-15.EL (raclinux1) 08/04/200402:02:34 AM CPU %user %nice %system %idle02:02:36 AM all 1.14 0.00 1.71 97.1402:02:38 AM all 2.62 0.00 3.66 93.7202:02:40 AM all 0.54 0.00 3.78 95.68Average: all 1.45 0.00 3.09 95.46

# sar -u <interval> <count>

• What is my CPU doing?: sar

CPU Activity - iostat

# iostat -c 2 3Linux 2.4.21-15.EL (raclinux1) 08/04/2004avg-cpu: %user %nice %sys %idle 5.73 0.00 17.16 77.11avg-cpu: %user %nice %sys %idle 4.62 0.00 27.18 68.21avg-cpu: %user %nice %sys %idle 9.55 0.00 35.96 54.49

# iostat -c <interval> <count>

• What is my CPU doing?: iostat

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)

Swap

Swap space (disk)

Physical memory (RAM)

Virtual memory

Swapped-in pages

Swapped-out pages

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

Memory Usage

Kernel (not paged)

Shared memory

Process memory

Process memory

Process memory

Page cache

Buffer cache

Kernel modules

Dynamically adjusted

Paged

Paged/locked

Not paged

• 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

Measuring Memory UsagePage outPa

ge in

No Free Memory?• free command 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

Memory - sar• -B paging statistics• -R memory statistics• -W swapping statistics

#sar -B <frequency> <count>

#sar -R <frequency> <count>


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


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

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


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


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/


System Wide• RDA (Remote Diagnostic Agent)

– http://set.oraclecorp.com/tools/dca/index.html• Lshw (Hardware Lister)

– http://freshmeat.net/projects/lshw/


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

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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

Documents

Linux 操作系统 系统优化

Linux 操作系统系统优化