--- name: "vmstat" section: "8" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["linux", "freebsd", "openbsd"] url: "https://new.carta.tech/vmstat" --- # vmstat(8) report virtual memory statistics ## NAME **vmstat** – report virtual memory statistics ## SYNOPSIS **vmstat** \[**--libxo**\] \[**-afHhimoPsz**\] \[**-M** *core* \[**-N** *system*\]\] \[**-c** *count*\] \[**-n** *devs*\]\[ **-p** *type*,*if*,*pass*\] \[**-w** *wait*\] \[*disks* *...*\] \[wait \[count\]\] ## DESCRIPTION The **vmstat** utility reports certain kernel statistics kept about process, virtual memory, disk, trap and cpu activity. If the **-M** option is not specified, information is obtained from the currently running kernel via the [sysctl(3)](/sysctl/3.md) interface. Otherwise, information is read from the specified core file, using the name list from the specified kernel image (or from the default image). The options are as follows: - **--libxo** Generate output via [libxo(3)](/libxo/3.md) in a selection of different human and machine readable formats. See [xo\_options(7)](/xo_options/7.md) for details on command line arguments. - **-a** When used with **-i**, include statistics about interrupts that have never been generated. - **-c** 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 repeat *count* is specified, and **-w** is specified, the default is infinity, otherwise the default is one. - **-f** Report on the number [fork(2)](/fork/2.md), [vfork(2)](/vfork/2.md) and [rfork(2)](/rfork/2.md) system calls since system startup, and the number of pages of virtual memory involved in each. - **-h** Changes memory columns into more easily human readable form. The default if standard output is a terminal device. - **-H** Changes memory columns into straight numbers. The default if standard output is not a terminal device (such as a script). - **-i** Report on the number of interrupts taken by each device since system startup. - **-M** Extract values associated with the name list from the specified *core*. - **-N** If **-M** is also specified, extract the name list from the specified *system* instead of the default, which is the kernel image the system has booted from. - **-m** Report on the usage of kernel dynamic memory allocated using [malloc(9)](/malloc/9.md) by type. - **-n** Change the maximum number of disks to display from the default of 2. - **-o** Display a list of virtual memory objects in the system and the resident memory used by each object. - **-P** Report per-cpu system/user/idle cpu statistics. - **-p** Specify which types of devices to display. There are three different categories of devices: - device type: - da Direct Access devices - sa Sequential Access devices - printer Printers - proc Processor devices - worm Write Once Read Multiple devices - cd CD devices - scanner Scanner devices - optical Optical Memory devices - changer Medium Changer devices - comm Communication devices - array Storage Array devices - enclosure Enclosure Services devices - floppy Floppy devices - interface: - IDE Integrated Drive Electronics devices - SCSI Small Computer System Interface devices - NVME NVM Express Interface devices - other Any other device interface - passthrough: - pass Passthrough devices The user must specify at least one device type, and may specify at most one device type from each category. Multiple device types in a single device type statement must be separated by commas. Any number of **-p** arguments may be specified on the command line. All **-p** arguments are ORed together to form a matching expression against which all devices in the system are compared. Any device that fully matches any **-p** argument will be included in the **vmstat** output, up to two devices, or the maximum number of devices specified by the user. - **-s** Display the contents of the *sum* structure, giving the total number of several kinds of paging related events which have occurred since system startup. - **-w** Pause *wait* seconds between each display. If no repeat *wait* interval is specified, the default is 1 second. The **vmstat** command will accept and honor a non-integer number of seconds. - **-z** Report on memory used by the kernel zone allocator, [uma(9)](/uma/9.md), by zone. The *wait* and *count* arguments may be given after their respective flags at any point on the command line before the *disks* argument(s), or without their flags, as the final argument(s). The latter form is accepted for backwards compatibility, but it is preferred to use the forms with **-w** and **-c** to avoid ambiguity. By default, **vmstat** displays the following information: - procs Information about the number of threads in various states: - r running or in run queue - b blocked for resources (i/o, paging, etc.) - w swapped out - memory Information about the usage of virtual and real memory. Mapped virtual memory is a sum of all of the virtual pages belonging to mapped virtual memory objects. Note that the entire memory object's size is considered mapped even if only a subset of the object's pages are currently mapped. This statistic is not related to the active page queue which is used to track real memory. - avm mapped virtual memory (previously called active in **vmstat** output) - fre size of the free list - page Information about page faults and paging activity. These are given in units per second. - flt total number of page faults - re pages reactivated (found in laundry or inactive queues) - pi pages paged in - po pages paged out - fr pages freed - sr pages scanned by page daemon - disks Disk operations per second (this field is system dependent). Typically paging will be split across the available drives. The header of the field is the first two characters 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, unless the user specifies the **-n** argument to increase the number of drives displayed. This will probably cause the display to exceed 80 columns, however. To force **vmstat** to display specific drives, their names may be supplied on the command line. The **vmstat** utility defaults to show disks first, and then various other random devices in the system to add up to two devices, if there are that many devices in the system. If devices are specified on the command line, or if a device type matching pattern is specified (see above), **vmstat** will only display the given devices or the devices matching the pattern, and will not randomly select other devices in the system. - faults Trap/interrupt rates per second. - in device interrupts (including clock interrupts) - sy system calls - cs cpu context switches - cpu Breakdown of percentage usage of CPU time. - us user time for normal and low priority processes - sy system and interrupt time - id cpu idle ## FILES - */boot/kernel/kernel* default kernel namelist - */dev/kmem* default memory file ## EXAMPLES The command: ``` vmstat -w 5 ``` will print what the system is doing every five seconds. The command: ``` vmstat -p da -p cd -w 1 ``` will tell vmstat to select the first two direct access or CDROM devices and display statistics on those devices, as well as other systems statistics every second. ## SEE ALSO [fstat(1)](/fstat/1.md), [netstat(1)](/netstat/1.md), [nfsstat(1)](/nfsstat/1.md), [ps(1)](/ps/1.md), [systat(1)](/systat/1.md), [libmemstat(3)](/libmemstat/3.md), [libxo(3)](/libxo/3.md), [xo\_options(7)](/xo_options/7.md), [gstat(8)](/gstat/8.md), [iostat(8)](/iostat/8.md), [pstat(8)](/pstat/8.md), [sysctl(8)](/sysctl/8.md), [malloc(9)](/malloc/9.md), [uma(9)](/uma/9.md) The sections starting with \`\`Interpreting system activity'' in ## HISTORY The **vmstat** utility first appeared in 3BSD. ## BUGS The **-c** and **-w** options are only available with the default output.