understanding vmstat

understanding vmstat

vmstat provides information about "processes", "memory", "paging", "block I/O", "traps" and "cpu" activity.

vmstat -n 2 10 [ generates vmstat 10 times with a sampling rate of two seconds. ]

process (procs):
 r: The number of processes waiting for runtime.
 b: The number of processes in uninterpretable sleep.

Memory:
 swpd: the amount of virtual memory used (KB)
 free: The amount of idle memory (KB)
 buff: the amount of memory used as buffers (KB)
 cache: The amount of memory used as cache (KB)

swap:
 si: Amount of memory swapped from the disk. (KB/s)
 so: Amount of memory swapped to the disk. (KB/s)

IO:
 bi: Blocks sent to a block device (blocks/s)
 bo: Blocks received from a block device (blocks/s)

system:
 in: The number of interrupts per seconds, including the clock.
 cs: The number of context switches per seconds.

cpu (% of total cpu time)
 us: Time spent running non-kernal code (user time, including nice time)
 sy: Time spent running kernel code  (system time)
 id: Time spent idle. (prior to linux 2.5.41, this included I/O-wait time. )
 wa: Time spent waiting for I/O. (prior to Linux 2.5.41, this appeared as zero)

some useful flags:

 -m: display the memory utilization of the kernal (slabs)
 -a: provides information about about active and inactive memory pages.
 -n: displays only one header line.
 -p: {partition} flag, vmstat also provides I/O statistics.