---
name: "vmstat"
section: "8"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["linux", "freebsd", "openbsd"]
url: "https://new.carta.tech/vmstat"
---

# vmstat(8)

report statistics about kernel activities

## NAME

**vmstat** – report statistics about kernel activities

## SYNOPSIS

**vmstat** \[**-fimstvz**\]

**vmstat** \[**-c** *count*\] \[**-M** *core*\] \[**-N** *system*\] \[**-w** *wait*\] \[*disk* *...*\]

## DESCRIPTION

**vmstat** reports certain kernel statistics kept about process, virtual memory, disk, trap, and CPU activity. The default behavior is to print a one-line summary of these statistics. The **-c** and **-w** flags may be used to continually report summaries.

The options are as follows:

- **-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.

- **-f**

  Report on the number of [fork(2)](/fork/2.md), \_\_tfork(3), and [vfork(2)](/vfork/2.md) system calls as well as kernel thread creations since system startup, and the number of pages of virtual memory involved in each.

- **-i**

  Report on the number of interrupts taken by each device since system startup.

- **-M** *core*

  Extract values associated with the name list from the specified core instead of the running kernel.

- **-m**

  Report on the usage of kernel dynamic memory listed first by size of allocation and then by type of usage.

- **-N** *system*

  Extract the name list from the specified system instead of the running kernel.

- **-s**

  Display the contents of the *uvmexp* structure (see uvm\_init(9)), giving the total number of several kinds of paging related events which have occurred since system startup.

- **-t**

  Report on the number of page in and page reclaims since system startup, and the amount of time required by each.

- **-v**

  Print more verbose information.

- **-w** *wait*

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

- **-z**

  When used with **-i**, also list devices which have not yet generated an interrupt.

By default, **vmstat** displays the following information just once:

- procs

  Information about the numbers of processes in various states.

  - r

    in run queue

  - s

    sleeping

- memory

  Information about the usage of virtual and real memory.

  - avm

    active virtual pages

  - fre

    size of the free list

- page

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

  - flt

    page faults

  - re

    page reclaims (simulating reference bits)

  - pi

    pages paged in

  - po

    pages paged out

  - fr

    pages freed

  - sr

    pages scanned by clock algorithm

- 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 two disk drives are configured in the system, **vmstat** displays only the first two drives. To force **vmstat** to display specific drives, their names may be supplied on the command line.

- traps

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

  - int

    device interrupts per interval (including clock interrupts)

  - sys

    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

- */bsd*

  default kernel image

- */dev/kmem*

  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)](/fstat/1.md), [netstat(1)](/netstat/1.md), [nfsstat(1)](/nfsstat/1.md), [procmap(1)](/procmap/1.md), [ps(1)](/ps/1.md), [systat(1)](/systat/1.md), [top(1)](/top/1.md), [iostat(8)](/iostat/8.md), [pstat(8)](/pstat/8.md), uvm\_init(9)

## BUGS

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

This manual page lacks an incredible amount of detail.