Hack 97. vmstat Command Examples

For a typical performance monitoring all you need is only vmstat command. This display memory, swap, IO, system and cpu performance information.

The following command executes vmstat every 1 second for 100 times.

# vmstat 1 100
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 0  0      0 282120 134108 5797012    0    0     0     2    0     0  0  0 100  0
 0  0      0 282120 134108 5797012    0    0     0     0 1007   359  0  0 100  0
 0  0      0 282120 134108 5797012    0    0     0     0 1117   577  0  0 100  0
 0  0      0 282120 134108 5797012    0    0     0     0 1007   366  0  0 100  0

Vmstat procs Section

  • r field: Total number of runnable process
  • b field: Total number of blocked process

Memory section

  • Swpd field: Used swap space
  • Free field: Available free RAM
  • Buff field: RAM used for buffers
  • Cache field: RAM used for filesystem cache

Swap Section

  • Si field: Amount of memory swapped from disk per second
  • So field: Amount of memory swapped to disk per second

IO Section

  • Bi field: Blocks received from disk
  • Bo field: Blocks sent to disk.

System Section

  • In field: Number of interrupts per second.
  • Cs field: Number of context switches per second.

CPU Section

  • Us field: Time spend running user code. (non-kernel code)
  • Sy field: Time spent running kernel code.
  • Id field: Idle time.
  • Wa field: Time spent waiting for the IO

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