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Linux 操作系统 系统优化. 周炯 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 to UNIX platforms: System Activity Reporter: sar Historical database

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linux

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.

slide2
内容提要
  • Performance concepts and measurement tools:
    • CPU
    • Memory
    • Disk I/O
    • Network
    • Process
    • Profiling Kernel & Applications

Acegene IT Co. Ltd.

measurement tools
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
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
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

cpu activity sar
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

cpu activity iostat
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

linux virtual memory
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)
slide9
Swap

Swapped-in pages

Physical

memory (RAM)

Swapped-out pages

Virtual memory

Swap space (disk)

measuring swap
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
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)

measuring memory usage

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
no free memory
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
memory sar
Memory - sar
  • -B paging statistics
  • -R memory statistics
  • -W swapping statistics

#sar -B <frequency> <count>

#sar -R <frequency> <count>

measuring disk i o
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.

network traffic
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.

sar flags
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
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.

what does the kernel do
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.

system wide
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.

summary linux monitoring tools
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.

slide22

Q

&

Q U E S T I O N S

A N S W E R S

A

slide23
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.