NAME

vmstat − report virtual memory statistics

SYNOPSIS

vmstat [ −s ] [ interval [ count ] ]

DESCRIPTION

Vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and cpu activity.  If given a −s argument, it instead prints the contents of the sum structure, giving 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. 

RQin run queue
DWdisk wait
SWrunnable or short sleeper (< 20 secs) but swapped

Memory: information about the usage of virtual and real memory. Virtual pages are considered active if they belong to processes which are running or have run in the last 20 seconds. A “page” here is 1024 bytes.

AVMactive virtual pages
TXpercent of active pages which are shared text
FREsize of the free list

Swap: information about the swapping activity of the system.

Iprocess swap ins in last 5 seconds
Oprocess swap outs in last 5 seconds

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

D0disk 0
D1disk 1
D2disk 2
D3disk 3

Faults: trap/interrupt over last 5 seconds.

INdevice interrupts (per second)
SYsystem calls (per second)
TRtraps (per second)
OVoverlay traps (in 5 second period)
CScpu context switch rate (switches/sec)

Cpu: breakdown of percentage usage of CPU time

USuser time for normal processes
NIuser time for low priority processes
SYsystem time
IDcpu idle

FILES

/dev/kmem, /unix

SEE ALSO

The sections starting with “Interpreting system activity” in Setting up the Fourth Berkeley Software Tape by W. Joy, O. Babaoglu, and K. Sklower

AUTHORS

William Joy, Ozalp Babaoglu, and Mark Horton

BUGS

7th Edition  —  4/22/80