vmstat

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



NAME
       vmstat - Report virtual memory statistics

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

DESCRIPTION
       vmstat  reports  information about processes, memory, paging, block IO,
       traps, disks 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.


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

       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
       periodically.

       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 -D reports some summary statistics about disk activity.

       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.

FIELD DESCRIPTION FOR VM MODE
   Procs
       r: The number of processes waiting for run time.
       b: The number of processes in uninterruptible sleep.

   Memory
       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)

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

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

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

   CPU
       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.


FIELD DESCRIPTION FOR DISK MODE
   Reads
       total: Total reads completed successfully
       merged: grouped reads (resulting in one I/O)
       sectors: Sectors read successfully
       ms: milliseconds spent reading

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

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


FIELD DESCRIPTION FOR DISK PARTITION MODE
       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



FIELD DESCRIPTION FOR SLAB MODE
       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


NOTES
       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

FILES
       /proc/meminfo
       /proc/stat
       /proc/*/stat


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

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

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



Throatwobbler Ginkgo Labs         2009 Jan 9                         VMSTAT(8)