||FreeBSD System Manager's Manual
report virtual memory statistics
[disks ...] [wait [count]]
vmstat utility reports certain kernel statistics
kept about process, virtual memory, disk, trap and cpu activity.
-M option is not specified,
information is obtained from the currently running kernel via the
interface. Otherwise, information is read from the specified core file,
using the name list from the specified kernel image (or from the default
The options are as follows:
- Generate output via
in a selection of different human and machine readable formats. See
for details on command line arguments.
- When used with
-i, include statistics about
interrupts that have never been generated.
- 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
-w is specified, the default is
infinity, otherwise the default is one.
- Report on the number
system calls since system startup, and the number of pages of virtual
memory involved in each.
- Changes memory columns into more easily human readable form. The default
if standard output is a terminal device.
- Changes memory columns into straight numbers. The default if standard
output is not a terminal device (such as a script).
- Report on the number of interrupts taken by each device since system
- Extract values associated with the name list from the specified
-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.
- Report on the usage of kernel dynamic memory allocated using
- Change the maximum number of disks to display from the default of 2.
- Display a list of virtual memory objects in the system and the resident
memory used by each object.
- Report per-cpu system/user/idle cpu statistics.
- Specify which types of devices to display. There are three different
categories of devices:
- device type:
- Direct Access devices
- Sequential Access devices
- Processor devices
- Write Once Read Multiple devices
- CD devices
- Scanner devices
- Optical Memory devices
- Medium Changer devices
- Communication devices
- Storage Array devices
- Enclosure Services devices
- Floppy devices
- Integrated Drive Electronics devices
- Small Computer System Interface devices
- Any other device interface
- 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
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.
- Display the contents of the sum structure, giving the
total number of several kinds of paging related events which have occurred
since system startup.
- Pause wait seconds between each display. If no
repeat wait interval is specified, the default is 1
vmstat command will accept and honor a
non-integer number of seconds.
- Report on memory used by the kernel zone allocator,
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
-c to avoid
vmstat displays the following
- Information about the number of threads in various states:
- running or in run queue
- blocked for resources (i/o, paging, etc.)
- swapped out
- 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.
- mapped virtual memory (previously called active in
- size of the free list
- Information about page faults and paging activity. These are given in
units per second.
- total number of page faults
- pages reactivated (found in laundry or inactive queues)
- pages paged in
- pages paged out
- pages freed
- pages scanned by page daemon
- 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
vmstat will only display the given devices
or the devices matching the pattern, and will not randomly select other
devices in the system.
- Trap/interrupt rates per second.
- device interrupts (including clock interrupts)
- system calls
- cpu context switches
- Breakdown of percentage usage of CPU time.
- user time for normal and low priority processes
- system and interrupt time
- cpu idle
- default kernel namelist
- default memory file
will print what the system is doing every five seconds.
vmstat -w 5
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
vmstat -p da -p cd -w 1
The sections starting with ``Interpreting system activity'' in
Installing and Operating 4.3BSD.
vmstat utility first appeared in
-w options are only
available with the default output.
Visit the GSP FreeBSD Man Page Interface.
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