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VMSTAT(8) System Manager's Manual VMSTAT(8)

vmstat — report statistics about kernel activities

vmstat [-fimstvz]

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

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:

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.
Report on the number of fork(2), __tfork(3), and vfork(2) system calls as well as kernel thread creations since system startup, and the number of pages of virtual memory involved in each.
Report on the number of interrupts taken by each device since system startup.
core
Extract values associated with the name list from the specified core instead of the running kernel.
Report on the usage of kernel dynamic memory listed first by size of allocation and then by type of usage.
system
Extract the name list from the specified system instead of the running kernel.
Display the contents of the uvmexp structure (see uvm(9)), giving the total number of several kinds of paging related events which have occurred since system startup.
Report on the number of page in and page reclaims since system startup, and the amount of time required by each.
Print more verbose information.
wait
Pause wait seconds between each display. If no repeat count is specified, the default is infinity.
When used with -i, also list devices which have not yet generated an interrupt.

By default, vmstat displays the following information just once:

Information about the numbers of processes in various states.

in run queue
blocked for resources (I/O, paging, etc.)
runnable or short sleeper (< 20 secs) but swapped
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.

active virtual pages
size of the free list
Information about page faults and paging activity. These are averaged each five seconds, and given in units per second.

page faults
page reclaims (simulating reference bits)
pages attached (found in free list)
pages paged in
pages paged out
pages freed
pages scanned by clock algorithm
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.
Trap/interrupt rate averages per second over last 5 seconds.

device interrupts per interval (including clock interrupts)
system calls per interval
CPU context switch rate (switches/interval)
Breakdown of percentage usage of CPU time.

user time for normal and low priority processes
system time
CPU idle

/bsd
default kernel image
/dev/kmem
default memory file

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.

fstat(1), netstat(1), nfsstat(1), procmap(1), ps(1), systat(1), top(1), iostat(8), pstat(8), uvm(9)

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

This manual page lacks an incredible amount of detail.

March 30, 2016 OpenBSD-6.0