NAME

vmstat — report virtual memory statistics

SYNOPSIS

vmstat

[-CefHiLlmstUvW] [-c count] [-h hashname] [-M core] [-N system] [-u histname] [-w wait] [disks]

DESCRIPTION

vmstat reports certain kernel statistics kept about process, virtual memory, disk, trap, and CPU activity.

The options are as follows:

-C

Report on kernel memory caches. Combine with the -m option to see information about memory pools that back the caches.

-c count

Repeat the display count times. The first display is for the time since a reboot and each subsequent report is for the time period since the last display. If no wait interval is specified, the default is 1 second.

-e

Report the values of system event counters.

-f

Report fork statistics.

-H

Report all hash table statistics.

-h hashname

Report hash table statistics for hashname.

-i

Report the values of system interrupt counters.

-L

List all the hashes supported for -h and -H.

-l

List the UVM histories being maintained by the kernel.

-M core

Extract values associated with the name list from the specified core instead of the default /dev/mem.

-m

Report on the usage of kernel dynamic memory listed first by size of allocation and then by type of usage, followed by a list of the kernel memory pools and their usage.

-N system

Extract the name list from the specified system instead of the default /netbsd.

-s

Display the contents of the uvmexp structure. This contains various paging event and memory status counters.

-t

Display the contents of the vmtotal structure. This includes information about processes and virtual memory.

The process part shows the number of processes in the following states:

ru

on the run queue

dw

in disk I/O wait

pw

waiting for paging

sl

sleeping

The virtual memory section shows:

total-v

Total virtual memory

active-v

Active virtual memory in use

active-r

Active real memory in use

vm-sh

Shared virtual memory

avm-sh

Active shared virtual memory

rm-sh

Shared real memory

arm-sh

Active shared real memory

free

Free memory

All memory values are shown in number of pages.

-U

Dump all UVM histories.

-u histname

Dump the specified UVM history.

-v

Print more verbose information. When used with the -i, -e, or -m options prints out all counters, not just those with non-zero values.

-W

Print more verbose information about kernel memory pools.

-w wait

Pause wait seconds between each display. If no repeat count is specified, the default is infinity.

By default, vmstat displays the following information:

procs

Information about the numbers of processes in various states.

r

in run queue

b

blocked for resources (i/o, paging, etc.)

memory

Information about the usage of virtual and real memory. Virtual pages (reported in units of 1024 bytes) are considered active if they belong to processes which are running or have run in the last 20 seconds.

avm

active virtual pages

fre

size of the free list

page

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

flt

total page faults

re

page reclaims (simulating reference bits)

pi

pages paged in

po

pages paged out

fr

pages freed per second

sr

pages scanned by clock algorithm, per-second

disks

Disk transfers per second. Typically paging will be split across the available drives. The header of the field is the first character of the disk name and the unit number. If more than four disk drives are configured in the system, vmstat displays only the first four drives. To force vmstat to display specific drives, their names may be supplied on the command line.

faults

Trap/interrupt rate averages per second over last 5 seconds.

in

device interrupts per interval (including clock interrupts)

sy

system calls per interval

cs

CPU context switch rate (switches/interval)

cpu

Breakdown of percentage usage of CPU time.

us

user time for normal and low priority processes

sy

system time

id

CPU idle

FILES

/netbsd

default kernel namelist

/dev/mem

default memory file

EXAMPLES

The command “vmstat -w 5” will print 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. Others vary every second and running the output for a while will make it apparent which are recomputed every second.

SEE ALSO

fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), iostat(8), pstat(8)

The sections starting with “Interpreting system activity” in Installing and Operating 4.3BSD.

BUGS

The -c and -w options are only available with the default output.

The -l, -U, and -u options are useful only if the system was compiled with support for UVM history.