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Manual page for VMSTAT(8)

vmstat - report virtual memory statistics

SYNOPSIS

vmstat [ -cfisS ] [ interval [ count ] ]

DESCRIPTION

vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and CPU activity.

Without options, vmstat displays a one-line summary of the virtual memory activity since the system has been booted. If interval is specified, vmstat summarizes activity over the last interval seconds. If a count is given, the statistics are repeated count times.

For example, the following command displays a summary of what the system is doing every five seconds. This is a good choice of printing interval since this is how often some of the statistics are sampled in the system.

example% vmstat 5
procs     memory                       page      faults
r b w   avm  fre  re at  pi  po  fr  de  sr x0 x1 x2 x3  in   sy  cs  us  sy  id
2 0 0   918  286   0  0   0   0   0   0    0  1  0   0   0    4  12    5   3   5  91
1 0 0   846  254   0  0   0   0   0   0    0  6  0   1   0   42 153  31  7  40  54
1 0 0   840  268   0  0   0   0   0   0    0  5  0   0   0   27 103  25  8  26  66
1 0 0   620  312   0  0   0   0   0   0    0  6  0   0   0   26  76  25  6  27  67
CTRL-C
example%

The fields of vmstat's display are:

procs: Report the number of processes in each of the three following states:

r: in run queue
b: blocked for resources (i/o, paging, etc.)
w: runnable or short sleeper (< 20 secs) but swapped

memory: Report on usage of virtual and real memory. Virtual memory is considered active if it belongs to processes which are running or have run in the last 20 seconds.

avm: number of active virtual Kbytes
fre: size of the free list in Kbytes

page: Report information about page faults and paging activity. The information on each of the following activities is averaged each five seconds, and given in units per second.

re: page reclaims -- but see the -S option for how this field is modified.
at: number of attaches -- but see the -S option for how this field is modified.
pi: kilobytes per second paged in
po: kilobytes per second paged out
fr: kilobytes freed per second
de: anticipated short term memory shortfall in Kbytes
sr: pages scanned by clock algorithm, per-second

disk: Report number of disk operations per second (this field is system dependent). For Sun systems, four slots are available for up to four drives: ``x0'' (or ``s0'' for SCSI disks), ``x1'', ``x2'', and ``x3''.
faults: Report trap/interrupt rate averages per second over last 5 seconds.

in: (non clock) device interrupts per second
sy: system calls per second
cs: CPU context switch rate (switches/sec)

cpu: Give a breakdown of percentage usage of CPU time.

us: user time for normal and low priority processes
sy: system time
id: CPU idle

OPTIONS

-c: Report cache flushing statistics. By default, report the total number of each kind of cache flushed since boot time. The types are: user, context, region, segment, page, and partial-page.
-f: Report on the number of forks and vforks since system startup and the number of pages of virtual memory involved in each kind of fork.
-i: Report the number of interrupts per device. Autovectored interrupts (including the clock) are listed first.
-s: Display the contents of the sum structure, giving the total number of several kinds of paging-related events which have occurred since boot.
-S: Report on swapping rather than paging activity. This option will change two fields in vmstat's ``paging'' display: rather than the ``re'' and ``at'' fields, vmstat will report ``si'' (swap-ins), and ``so'' (swap-outs).

FILES

/dev/kmem
/vmunix

BUGS

If more than one autovectored device has the same name, interrupts are counted for all like-named devices regardless of unit number. Such devices are listed with a unit number of `?'.