The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length delay. The process and memory reports are instantaneous in either case.
delay is the delay between updates in seconds. If no delay is specified, only one report is printed with the average values since boot.
count is the number of updates. If no count is specified and delay is defined, count defaults to infinity.
The -V switch results in displaying version information.
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).
Swap si: Amount of memory swapped in from disk (kB/s).
so: Amount of memory swapped to 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 second, including the clock.
cs: The number of context switches per second.
CPU These are percentages of total CPU time.
us: user time
sy: system time
id: idle time
These reports are intended to help identify system bottlenecks. Linux vmstat does not count itself as a running process.
All linux blocks are currently 1k, except for CD-ROM blocks which are 2k.
/proc/meminfo
/proc/stat
/proc/*/stat