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NAME    [Toc]    [Back]

     vmstat -- report virtual memory statistics

SYNOPSIS    [Toc]    [Back]

     vmstat [-fimsz] [-c count] [-M core] [-N system] [-w wait] [-n devs] [-p
	    type,if,pass] [disks]

DESCRIPTION    [Toc]    [Back]

     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
	     system startup.

     -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
	     default /boot/kernel/kernel.

     -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:

	     device type:
		     da 	Direct Access devices
		     sa 	Sequential Access devices
		     printer	Printers
		     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
	     sysctl variable.

     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

EXAMPLES    [Toc]    [Back]

     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.

     The command:
	   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
 every second.

FILES    [Toc]    [Back]

     /boot/kernel/kernel  default kernel namelist
     /dev/kmem		  default memory file

SEE ALSO    [Toc]    [Back]

     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.

BUGS    [Toc]    [Back]

     The -c and -w options are only available with the default output.

FreeBSD 5.2.1			April 14, 2003			 FreeBSD 5.2.1
[ Back ]
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