# uname -r
2.6.32-358.14.1.el6.x86_64

全CPU100%にする為、わざと無限ループさせる
今回はCPU4つなので、4回実行する。

# python -c "while True: True" &
# python -c "while True: True" &
# python -c "while True: True" &
# python -c "while True: True" &

# vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 5  0      0 247944   8012 186900    0    0    20     6   62    6  5  0 90  0  5	
 4  0      0 247812   8012 186928    0    0     0     0 3492   63 11  0 88  0  1	
 4  0      0 247812   8012 186928    0    0     0     0 3488   45 11  0 88  0  2	
 4  0      0 247812   8012 186928    0    0     0     0 3356   36 10  0 87  0  2	
 4  0      0 247812   8012 186928    0    0     0     0 3467   38 11  0 87  0  2

Tasks: 132 total,   5 running, 127 sleeping,   0 stopped,   0 zombie
Cpu(s): 11.0%us,  0.0%sy,  0.0%ni, 87.5%id,  0.0%wa,  0.0%hi,  0.0%si,  1.6%st
Mem:    666700k total,   418648k used,   248052k free,     7848k buffers
Swap:  2097144k total,        0k used,  2097144k free,   186908k cached


 1571 root      20   0  112m 3732 1760 R 99.8  0.6   0:09.32 python                                                                                                    
 1573 root      20   0  112m 3728 1760 R 99.8  0.6   0:07.47 python                                                                                                    
 1572 root      20   0  112m 3724 1760 R 99.5  0.6   0:07.95 python                                                                                                    
 1574 root      20   0  112m 3728 1760 R 99.5  0.6   0:06.88 python 

top後、「1」を押して、CPUごとの使用率を表示させる

Tasks: 134 total,   5 running, 128 sleeping,   0 stopped,   1 zombie
Cpu0  : 99.7%us,  0.3%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu1  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:    666700k total,   574912k used,    91788k free,    11700k buffers
Swap:  2097144k total,        0k used,  2097144k free,   323568k cached


 1571 root      20   0  112m 3732 1760 R 100.0  0.6  26:38.39 python                                                                                                   
 1572 root      20   0  112m 3724 1760 R 99.7  0.6  26:37.16 python                                                                                                    
 1574 root      20   0  112m 3728 1760 R 99.7  0.6  26:34.97 python                                                                                                    
 1573 root      20   0  112m 3728 1760 R 99.4  0.6  26:36.89 python 

同じ事をした場合、CentOS 6.0ではちゃんとvmstatのidleは0になる。

# uname -r
2.6.18-274.3.1.el5xen

# vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 4  0      0 502296   9012 127460    0    0    30     3  103   15 95  0  4  1  0
 4  0      0 502296   9012 127460    0    0     0     0  410   33 100  0  0  0  0
 4  0      0 502296   9012 127460    0    0     0     0  410   28 100  0  0  0  0
 4  0      0 502296   9012 127460    0    0     0     0  410   34 100  0  0  0  0
<code>

==== top結果 ====

<code console>
top - 09:35:19 up 21 min,  1 user,  load average: 4.00, 3.96, 2.94
Tasks: 105 total,   5 running, 100 sleeping,   0 stopped,   0 zombie
Cpu(s):100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1048576k total,   546320k used,   502256k free,     9084k buffers
Swap:  2097144k total,        0k used,  2097144k free,   127452k cached


 2126 root      25   0 72172 2664 1344 R 100.0  0.3  20:17.04 python                                                                                                   
 2124 root      25   0 72172 2664 1344 R 100.0  0.3  20:19.48 python                                                                                                   
 2127 root      25   0 72172 2660 1344 R 100.0  0.3  20:16.56 python                                                                                                   
 2128 root      25   0 72172 2664 1344 R 99.7  0.3  20:16.12 python 

top後、「1」を押して、CPUごとの使用率を表示させる

Tasks: 105 total,   5 running, 100 sleeping,   0 stopped,   0 zombie
Cpu0  : 95.6%us,  0.1%sy,  0.0%ni,  2.6%id,  1.7%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu1  : 95.5%us,  0.1%sy,  0.0%ni,  4.1%id,  0.2%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  : 95.4%us,  0.1%sy,  0.0%ni,  4.5%id,  0.1%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  : 95.4%us,  0.1%sy,  0.0%ni,  4.3%id,  0.2%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1048576k total,   546312k used,   502264k free,     9148k buffers
Swap:  2097144k total,        0k used,  2097144k free,   127464k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                   
 2124 root      25   0 72172 2664 1344 R 100.0  0.3  21:02.59 python                                                                                                   
 2126 root      25   0 72172 2664 1344 R 100.0  0.3  21:00.12 python                                                                                                   
 2128 root      25   0 72172 2664 1344 R 100.0  0.3  20:59.23 python                                                                                                   
 2127 root      25   0 72172 2660 1344 R 97.8  0.3  20:59.65 python