NAME

vmstat − report virtual memory statistics

SYNTAX

vmstat [ interval [ count ] ]
vmstat −f
vmstat −s [ interval [ count ] ]
vmstat −k namelist [ corefile ]
vmstat −z

DESCRIPTION

The vmstat command reports statistics kept about processes, virtual memory, disk, trap 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, giving the total number of several kinds of paging related events that have occurred since boot.  If given a −z argument and if the UID indicates root privilege, the sum structure is zeroed out.  If given a −k argument and a namelist and corefile, a dump may be interrogated to print the contents of the sum structure (default). 

If none of these options is given, vmstat summarizes the virtual memory activity since the system was booted. If interval is specified, then successive lines are summaries of activity over the last interval seconds.  The command vmstat 5, for example, prints what the system is doing every five seconds. This is a good choice of printing interval since some of the statistics are sampled in the system every 5 seconds; others vary every second. If a count is given, the statistics are repeated count times. 

When you run vmstat the format fields are as follows:

Procs: information about numbers of processes in various states. 

rin run queue
bblocked for resources (i/o, paging, etc.)
wrunnable or short sleeper (< 20 secs) but swapped

Memory: information about the use 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 is 1024 bytes.

avmactive virtual pages
fresize of the free list
If the number of pages exceeds 9999, it is shown in a scaled
representation.  The suffix k indicates multiplication
by 1000 and the suffix m indicates multiplication by
1000000.  For example, the value 12345 appears as 12k.

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

repage reclaims (simulating reference bits)
atpages attached (found in free list not swapdev or filesystem)
pipages paged in
popages paged out
frpages freed per second
deanticipated short term memory shortfall
srpages scanned by clock algorithm, per-second

Disk:  up/hp/rk:  Disk operations per second (this field is system dependent). Typically paging is split across several of the available drives. The number under each of these is the unit number. Faults: trap/interrupt rate averages per second over the last 5 seconds.

in(non clock) device interrupts per second
sysystem calls per second
cscpu context switch rate (switches/sec)

Cpu: breakdown of percentage usage of CPU time

ususer time for normal and low priority processes
sysystem time
idcpu idle
If given a -S argument, the page reclaim (re)
and pages attached (at) fields are
replaced with:

siprocesses swapped in
soprocesses swapped out

OPTIONS

−fDisplays number of forks and vforks since system startup and number of pages of virtual memory involved in each kind of fork. 

−sDisplays total number of paging-related events occurring since boot. 

−SReplaces the page reclaim (re) and pages attached (at) fields with processes swapped in (si) and processes swapped out (so). 

−kAllows a dump to be interrogated to print the contents of the sum structure (default).  For vmstat to print the contents, however, the namelist and corefile arguments must be specified also. 

−zZeroes out the sum structure.  The user’s UID must indicate root privilege. 

FILES

/dev/kmem
/vmunix

Commands