VMSTAT(8)

NAME
vmstat - Report virtual memory statistics

SYNOPSIS
vmstat [-a] [-n] [delay [ count]]
vmstat [-f] [-s]
vmstat [-V]

DESCRIPTION
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity. 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.

  Options
The -a switch displays active/inactive memory, given a 2.5.41 kernel or better.

The -f switch displays the number of forks since boot. This includes the fork, vfork, and clone system calls, and is equivalent to the total number of tasks created. Each process is represented by one or more tasks, depending on thread usage. This display does not repeat.

The -n switch causes the header to be displayed only once rather than periodically.

The -s switch displays a table of various event counters and memory statistics. This display does not repeat.

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.

FIELD DESCRIPTIONS

  Procs
r: The number of processes waiting for run time.
b: The number of processes in uninterruptable 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).
inact: the amount of inactive memory (kB). (-a option)
active: the amount of active memory (kB). (-a option)

  Swap
si: Amount of memory swapped in from disk (kB/s).
so: Amount of memory swapped to disk (kB/s).

  IO
bi: Blocks received from a block device (blocks/s).
bo: Blocks sent to 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: Time spent running non-kernel 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 includes IO-wait time.
wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.

NOTES
vmstat does not require special permissions.

These reports are intended to help identify system bottlenecks. Linux vmstat does not count itself as a running process.

All linux blocks are currently 1024 bytes. Old kernels may report blocks as 512 bytes, 2048 bytes, or 4096 bytes.

FILES
/proc/meminfo
/proc/stat
/proc/*/stat

SEE ALSO
ps(1), top(1), free(1)

BUGS
Does not tabulate the block io per device or count the number of system calls.

AUTHOR
Written by Henry Ware <al172@yfn.ysu.edu>.