VMSTAT(1)

NAME
vmstat - report virtual memory statistics

SYNOPSIS
vmstat [ -fs ] [ interval [ count ] ]

DESCRIPTION
Vmstat delves into the system and reports certain statistics kept about process, virtual memory, disk and cpu activity. If given a -f argument, it reports on the number of forks and vforks since system startup and the number of pages of virtual memory involved in each kind of fork. If given a -s argument, it prints the contents of the sum structure, given the total number of several kinds of paging related events which have occurred since boot.

If none of these options are given, vmstat will report in a (usually) iterative fashion on the virtual memory activity in the system. In this case, the optional interval argument causes vmstat to report once each interval seconds; ``vmstat 5'' will print what the system is doing every five seconds; this is a good choice of printing interval since this is how often the statistics are sampled in the system. If a count is given, the statistics are repeated count times. The fields are:

Procs: information about numbers of processes in various states.

RQ	in run queue
DW	sleeping on short event (disk wait)
PW	in page wait
SL	sleeping for short time, and in main memory
SW	runnable or sleeping for a short time, but swapped out

Virtual: information about the state of virtual memory in the system.

AVM	active virtual pages
TX	percentage of active pages which were shared text pages

Real: information about the state of real memory in the system.

USE	page frames in use for data+text+stack of active processes
TX	percentage of USE which is text (shared program) pages
FRE	size of the free list

Fault: information about page faults and paging activity. These are averaged each five seconds, and given in units per second.

RE	page reclaims (simulating reference bits)
PI	pages paged in
PO	dirty page write back rate (pages per second)
FR	rate at which free list is replenished (pages per second)
SR	scan rate: pageout daemon rpm (this is in revs/minute)

Swp: information about the activity of the swap daemon (process 0).

I	process swap in rate (processes per 10 seconds)
O	process swap out rate (processes per 10 seconds)

Disk: operations per second (this field is system dependent).

RP	/usr (user) file transactions and root file activity
RM	paging and /tmp (temporary) file activity

Cpu: cpu context switch rate and breakdown of cpu usage by percentage in last few seconds.

CS	cpu context switch rate in switches per second

US	user time
SY	system time
ID	cpu idle

Any time not accounted for by US+SY+ID is given to low priority jobs.

FILES
/dev/kmem, /vmunix

SEE ALSO
The section on configuration in Setting up the Virtual Memory Extensions to the UNIX System by O. Babaoglu and W. Joy

AUTHORS
William Joy and Ozalp Babaoglu

BUGS
So many numbers print out that its sometimes hard to figure out what to watch.