report virtual memory statistics
utility reports certain kernel
statistics kept about process, virtual memory, disk, trap and cpu activity.
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 image).
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 specified, and
-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
- 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:
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
- 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
-p arguments may be
specified on the command line. All
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 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 second. The
command will accept and honor a non-integer number of seconds.
- Report on memory used by the kernel zone allocator,
arguments may be given after their
respective flags at any point on the command line before the
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
to avoid ambiguity.
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
- page reclaims (simulating reference bits)
- 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
display specific drives, their names may be supplied on the command line.
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 above),
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
vmstat -w 5
will print what the system is doing every five seconds.
vmstat -p da -p cd -w 1
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
The sections starting with ``Interpreting system activity'' in
Installing and Operating 4.3BSD.
options are only available with the