VMSTAT(1) BSD General Commands Manual VMSTAT(1)NAMEvmstat — report virtual memory statistics
SYNOPSISvmstat [-CefHiLlmstUvW] [-c count] [-h hashname] [-M core] [-N system]
[-u histname] [-w wait] [disks]
DESCRIPTIONvmstat reports certain kernel statistics kept about process, virtual mem‐
ory, 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 speci‐
fied 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 fol‐
lowing 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 char‐
acter 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 ALSOfstat(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.
BSD October 22, 2009 BSD
