Linux 操作系統跑Linux慢的分析

發表于:2007-05-26來源:作者:點擊數: 標簽:
挺詳細的。是好東東。 iostat的默認參數是td 默認參數將被完全替代,例 c(terminal, disk, and CPU)。 如,iostat -d將只反 映磁盤的 如果任何其他的選項被指定,這個 統計結果。 語法: 基本語法: iostat interval count option - 讓你指定所 。x 選項給出
挺詳細的。是好東東。

 

  iostat的默認參數是td
默認參數將被完全替代,例
c(terminal, disk, and CPU)。
如,iostat -d將只反 映磁盤的
如果任何其他的選項被指定,這個
統計結果。

  語法:

  基本語法: iostat interval count                       

  option - 讓你指定所
。x 選項給出了完整的統計
需信息的設備,像磁盤、cpu或
結果(gives the extended
者終端(-d , -c , -t or -tdc )


  statistic)。                                                       

  interval - 在兩個samples之間的時間(秒)。                 

  count - 就是需要統計幾次                                             

  例子:

  $ iostat -xtc 5 2                                           
  extended disk statistics tty cpu             
  disk r/s w/s Kr/s Kw
/s wait actv svc_t %w %b tin
tout us sy wt id
  sd0 2.6 3.0 20.7 22.7 0.1 0.2 59
.2 6 19 0 84 3 85 11 0
  sd1 4.2 1.0 33.5 8.0 0.0 0.2 47.2 2 23
  sd2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0       
  sd3 10.2 1.6 51.4 12.8 0.1 0.3 3
1.2 3 31


  The fields have the
following meanings:

  disk name of the disk                                   
  r/s reads per second                                     
  w/s writes per second                                   
  Kr/s kilobytes read per second                 
  Kw/s kilobytes written per second           
  wait average number of transacti
ons waiting for service (Q length)

  actv average number
of transactions actively
  being serviced (removed from the             
  queue but not yet                                           
  completed)                                                         
  %w percent of time t
here are transactions waitin
g
  for service (queue non-empty)                   
  %b percent of time t
he disk is busy (transaction
s
  in progress)                                                     

  Results and Solutions:                                 

  從iostat輸出結果中需要注意的值:                                       

  Reads/writes per second (r/s , w/s)       
  Percentage busy (%b)                                     
  Service time (svc_t)                                     

  如果磁盤顯示長時間的高reads/writ
同時average service time (svc_t)也遠
es,并且磁盤的percentage busy (%b)也遠大于5%,
大于30

  milliseconds,這以下的措施需要被執行:                           
  1.)調整應用,令其使用磁盤i/o更加
cache
有效率,可以通過修改磁盤隊列、使用應用服務器


  2.)將文件系統分布到2

個或多個磁盤上,并使用volume

manager/disksuite的條帶化特點


  3.) 增加系統參數值,
values for inode cache ,
如inode cache , ufs_ninode。
ufs_ninode , which
Increase the system parameter


  is Number of inodes to be held i
UFS), not on a per-file system basis
n memory. Inodes are cached globally (for


  4.) 將文件系統移到更快的磁盤/控制器,或者用更好的設備來代替              
  vmstat - vmstat反映
?)和cpu的活動情況
了進程的虛擬內存、虛擬內存、

磁盤、trap(是不是翻譯成中斷?


  在多cpu系統中,vmsta
果沒有選項,vmstat顯示一
t在輸出結果中平均了cpu數量。
行虛擬內存活動的概要
For per-process statistics .如


  結果,是從系統啟動時開始的。                                                 

  語法:

  vmstat interval count                                   

  option - 讓你指定所需的信息類型
etc.
,例如 paging -p , cache -c ,.interrupt -i


  如果沒有指定選項,將會顯示進程、內存、頁、磁盤、中斷和cpu信息             

  interval - 同iostat                                         

  count - 同iostat                                               

  例子                                                                         
  The following comman
d displays a summary of what
the system
  is doing every five seconds.                     

  example% vmstat 5                                           
  procs memory page disk faults cpu           
  r b w swap free re mf pi p fr de
sr s0 s1 s2 s3 in sy cs us sy id
  0 0 0 11456 4120 1 4
1 19 1 3 0 2 0 4 0 0 48 112
130 4 14 82
  0 0 1 10132 4280 0 4
44 0 0 0 0 0 23 0 0 211 230
144 3 35 62
  0 0 1 10132 4616 0 0 20 0 0 0 0
0 19 0 0 150 172 146 3 33 64
  0 0 1 10132 5292 0 0
9 0 0 0 0 0 21 0 0 165 105
130 1 21 78

  The fields of vmstat's display are         
  procs                                                                   
  r in run queue                                                 
  b blocked for resources I/O, pag
ing etc.
  w swapped                                                           

  memory (in Kbytes)                                         
  swap - amount of swap space curr
ently available
  free - size of the free list                     

  page ( in units per second).                     
  re page reclaims - s
ee -S option for how this fi
eld is modified.
  mf minor faults - se
e -S option for how this fie
ld is modified.
  pi kilobytes paged in                                   
  po kilobytes paged out                                 
  fr kilobytes freed                                         
  de anticipated short-term memory
shortfall (Kbytes)
  sr pages scanned by clock algorithm       

  disk ( operations per second )                 
  There are slots for up to four d

isks, labeled with a single letter and number.

  The letter indicates

the type of disk (s = SCSI,

i = IPI, etc) . The number is

  the logical unit number.                             

  faults                                                                 
  in (non clock) device interrupts             
  sy system calls                                               
  cs CPU context switches                               

  cpu - breakdown of p
an a
ercentage usage of CPU time.

On multiprocessors this is

  verage across all processors.                   
  us user time                                                     
  sy system time                                                 
  id idle time                                                     

  結果和解決方案:

  A. CPU issues:                                                 

  下面幾列需要被察看,以確定cpu是否有問題                                   

  Processes in the run queue (procs r)     
  User time (cpu us)                                         
  System time (cpu sy)                                     
  Idle time (cpu id)                                         
  procs cpu                                                           
  r b w us sy id                                                 
  0 0 0 4 14 82                                                   
  0 0 1 3 35 62                                                   
  0 0 1 3 33 64                                                   
  0 0 1 1 21 78                                                   

  問題情況:

  1.) 如果processes in
統便慢。
run queue (procs r)的數量遠

大于系統中cpu的數量,將會使系

  2.) 如果這個數量是cp
幅度降低
u的4倍的話,說明系統正面臨cp

u能力短缺,這將使系統運行速度大

  3.) 如果cpu的idle時
(cpu us)兩輩的話,系統面
間經常為0的話,或者系統占用
臨缺少cpu資源
時間(cpu sy)是用戶占用時間


  解決方案 :

  解決這些情況,涉及到調整應用程序
量。
,使其能更有效的使用cpu,同時增加cpu的能力或數


  B. Memory Issues:                                           
  內存的瓶頸取決于scan
is the pages scanned by
rate (sr) 。scan rate是每秒
the clock algorithm per
時鐘對頁的掃描 (he scan rate


  second.)如果 scan r
ate (sr)一直大于200 pages每
秒,這時就是內存短缺的現實。

  解決方案 :

  1. 調整應用和服務器,使其能更好的使用memory和cache             
  2. 增加系統內存                                                            
  dmidecode類似AIX的lsdev,所有的設備基本都可以看到。          

原文轉自:http://www.anti-gravitydesign.com

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