vmstat -- report virtual memory statistics
vmstat [-fimsz] [-c count] [-M core] [-N system] [-w wait] [-n devs] [-p
The vmstat utility reports certain kernel statistics kept about process,
virtual memory, disk, trap and cpu activity.
The options are as follows:
-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), vfork(2) and rfork(2) system calls
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
-M Extract values associated with the name list from the specified
core instead of the default /dev/kmem.
-N Extract the name list from the specified system instead of the
-m Report on the usage of kernel dynamic memory listed first by size
of allocation and then by type of usage.
-n Change the maximum number of disks to display from the default of
-p Specify which types of devices to display. There are three different
categories of devices:
da Direct Access devices
sa Sequential Access devices
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
IDE Integrated Drive Electronics devices
SCSI Small Computer System Interface devices
other Any other device interface
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 three 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.
-z Report on memory used by the kernel zone allocator, by zone. The
information shown is the same as that returned by the vm.zone
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.)
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 total number of 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 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 three disk drives are configured
in the system, vmstat displays only the first three 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 three 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 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
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.
vmstat -p da -p cd -w 1
will tell vmstat to select the first three direct access or CDROM devices
and display statistics on those devices, as well as other systems statistics
/boot/kernel/kernel default kernel namelist
/dev/kmem default memory file
fstat(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.
The -c and -w options are only available with the default output.
FreeBSD 5.2.1 April 14, 2003 FreeBSD 5.2.1 [ Back ]