Name

vmstat − report virtual memory statistics

Syntax

vmstat [ interval [ count ] ]
vmstat −vS [ interval [ count ] ]
vmstat −fKsz
vmstat −Kks namelist [ corefile ]

Description

The vmstat command reports statistics on processes, virtual memory, disk, trap, and cpu activity.

If vmstat is specified without arguments, this command summarizes the virtual memory activity since the system was last booted.  If the interval argument is specified, then successive lines are summaries of activity over the last interval seconds.  Because many statistics are sampled in the system every five seconds, five is a good specification for interval; other statistics vary every second.  If the count argument is provided, 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, and so on.) 

wrunnable or short sleeper (< 20 seconds) but swapped

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/second)

cpu:  breakdown of percentage usage of cpu time

ususer time for normal and low priority processes

sysystem time

idcpu idle time

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. 

avmactive virtual pages

fresize of the free list

Pages are reported in units of 1024 bytes. 

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.  The size of a unit is always 1024 bytes and is independent of the actual page size on a machine. 

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:  s0, s1 ...sn: Paging/swapping disk sector transfers per second (this field is system dependent).  Typically paging is split across several of the available drives.  This will print for each paging/swapping device configured into the kernel. 

Options

−fProvides 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. 

−KDisplays usage statistics of the kernel memory allocator. 

−kAllows a dump to be interrogated to print the contents of the sum structure when specified with a namelist and corefile.  This is the default. 

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

−sPrints the contents of the sum structure, giving the total number of several kinds of paging related events that have occurred since boot. 

−vPrints an expanded form of the virtual memory statistics. 

−zZeroes out the sum structure if the UID indicates root privilege. 

Examples

The following command prints what the system is doing every five seconds:

vmstat 5

To find the status after a core dump use the following:

cd /usr/adm/crash
vmstat −k vmunix.? vmcore.?

Files

/dev/kmem
Kernel memory

/vmunix System namelist