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vmstat - report virtual memory statistics



      vmstat - report virtual memory statistics


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


      The vmstat utility reports certain kernel statistics kept about process,
      virtual memory, disk, trap and cpu activity.
      If the -M option is not specified, information is obtained from the cur‐
      rently running kernel via the sysctl(3) interface.  Otherwise, informa‐
      tion 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:
      -a      When used with -i, include statistics about interrupts that have
              never been generated.
      -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
      -N      If -M is also specified, extract the name list from the specified
              system instead of the default, which is the kernel image the sys‐
              tem has booted from.
      -m      Report on the usage of kernel dynamic memory allocated using
              malloc(9) by type.
      -n      Change the maximum number of disks to display from the default of
      -p      Specify which types of devices to display.  There are three dif‐
              ferent 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 com‐
              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 two devices, or the maximum number of devices spec‐
              ified by the user.
      -s      Display the contents of the sum structure, giving the total num‐
              ber 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, uma(9), by
      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 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 ran‐
              dom 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.
      faults  Trap/interrupt rate averages per second over last 5 seconds.
              in      device interrupts per interval (including clock inter‐
              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


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


      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 statis‐
      tics are sampled in the system.  Others vary every second and running the
      output for a while will make it apparent which are recomputed every sec‐
      The command:
            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 statis‐
      tics every second.
      fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), libmemstat(3),
      gstat(8), iostat(8), pstat(8), sysctl(8), malloc(9), uma(9)
      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.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.