Skip to main content

vmstat command man page

VMSTAT(8) Linux Administrator’s Manual     VMSTAT(8)

       vmstat - Report virtual memory statistics

       vmstat [-a] [-n] [-S unit] [delay [ count]]
       vmstat [-s] [-n] [-S unit]
       vmstat [-m] [-n] [delay [ count]]
       vmstat [-d] [-n] [delay [ count]]
       vmstat [-p disk partition] [-n] [delay [ count]]
       vmstat [-f]
       vmstat [-V]

       vmstat  reports information about processes, memory, paging, block IO,
       traps, and cpu activity.

       The first report produced gives averages since the last reboot. Addi-
       tional  reports give information on a sampling period of length delay.
       The process and memory reports are instantaneous in either case.

       The -a switch displays active/inactive memory, given a 2.5.41 kernel or

       The  -f switch displays the number of forks since boot. This includes
       the fork, vfork, and clone system calls, and is equivalent to the total
       number  of  tasks  created.  Each process is represented by one or more
       tasks, depending on thread usage.  This display does not repeat.

       The -m displays slabinfo.

       The -n switch causes the header to be displayed only once  rather  than

       The  -s switch displays  a table of various event counters and memory
       statistics. This display does not repeat.

       delay is the delay between updates in seconds.  If no delay  is speci-
       fied, only one report is printed with the average values since boot.

       count  is the number of updates. If no count is specified and delay is
       defined, count defaults to infinity.

       The -d reports disk statistics (2.5.70 or above required)

       The -w enlarges field width for big memory sizes

       The -p followed by some partition name for detailed statistics  (2.5.70
       or above required)

       The  -S followed  by  k or K or m or M switches outputs between 1000,
       1024, 1000000, or 1048576 bytes

       The -V switch results in displaying version information.

       r: The number of processes waiting for run time.
       b: The number of processes in uninterruptible sleep.

       swpd: the amount of virtual memory used.
       free: the amount of idle memory.
       buff: the amount of memory used as buffers.
       cache: the amount of memory used as cache.
       inact: the amount of inactive memory. (-a option)
       active: the amount of active memory. (-a option)

       si: Amount of memory swapped in from disk (/s).
       so: Amount of memory swapped to disk (/s).

       bi: Blocks received from a block device (blocks/s).
       bo: Blocks sent to a block device (blocks/s).

       in: The number of interrupts per second, including the clock.
       cs: The number of context switches per second.

       These are percentages of total CPU time.
       us: Time spent running non-kernel code. (user time, including nice time)
       sy: Time spent running kernel code. (system time)
       id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
       wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle.
       st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.

       total: Total reads completed successfully
       merged: grouped reads (resulting in one I/O)
       sectors: Sectors read successfully
       ms: milliseconds spent reading

       total: Total writes completed successfully
       merged: grouped writes (resulting in one I/O)
       sectors: Sectors written successfully
       ms: milliseconds spent writing

       cur: I/O in progress
       s: seconds spent for I/O

       reads: Total number of reads issued to this partition
       read sectors: Total read sectors for partition
       writes : Total number of writes issued to this partition
       requested writes: Total number of write requests made for partition

       cache: Cache name
       num: Number of currently active objects
       total: Total number of available objects
       size: Size of each object
       pages: Number of pages with at least one active object
       totpages: Total number of allocated pages
       pslab: Number of pages per slab

       vmstat does not require special permissions.

       These reports are intended to help identify system bottlenecks. Linux
       vmstat does not count itself as a running process.

       All  linux  blocks  are currently  1024 bytes. Old kernels may report
       blocks as 512 bytes, 2048 bytes, or 4096 bytes.

       Since procps 3.1.9, vmstat lets you choose units (k, K, m,  M)  default
       is K (1024 bytes) in the default mode

       vmstat uses slabinfo 1.1   FIXME


       iostat(1), sar(1), mpstat(1), ps(1), top(1), free(1)

       Does not tabulate the block io per device or count the number of system

       Written by Henry Ware <>.
       Fabian Frédérick <> (diskstat, slab, partitions...)

Throatwobbler Ginkgo Labs 27 July 1994     VMSTAT(8)


Popular posts from this blog

Find and replace with sed command in Linux

Find and replace feature is always handy. It can turn into a torture when it comes to change or delete a simple constant string in a text file. There is a handy tool in linux for doing these kind of tihngs. Actually sed is not a text editor but it is used outside of the text file to make changes.