VMSTAT(8) System Manager's Manual VMSTAT(8)
vmstat - report statistics about kernel activities
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:
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), __tfork(2), 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.
-i Report on the number of interrupts taken by each device since
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.
Extract the name list from the specified system instead of the
-s 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.
-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.
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
By default, vmstat displays the following information just once:
procs Information about the numbers of processes in various states.
r in run queue
b blocked for resources (I/O, paging, etc.)
w runnable or short sleeper (< 20 secs) but swapped
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 each five seconds, and given in units per second.
flt page faults
re page reclaims (simulating reference bits)
at pages attached (found in free list)
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
/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.
OpenBSD 5.9 April 12, 2012 OpenBSD 5.9
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