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VMSTAT(8)                             System Administration                             VMSTAT(8)

NAME
       vmstat - Report virtual memory statistics

SYNOPSIS
       vmstat [options] [delay [count]]

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.  Additional  reports  give
       information  on a sampling period of length delay.  The process and memory reports are in-
       stantaneous in either case.

OPTIONS
       delay  The delay between updates in seconds.  If no delay is specified, only one report is
              printed with the average values since boot.

       count  Number  of  updates.   In absence of count, when delay is defined, default is infi-
              nite.

       -a, --active
              Display active and  inactive memory, given a 2.5.41 kernel or better.

       -f, --forks
              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 cre-
              ated.  Each process is represented by one or more tasks, depending on thread usage.
              This display does not repeat.

       -m, --slabs
              Displays slabinfo.

       -n, --one-header
              Display the header only once rather than periodically.

       -s, --stats
              Displays  a  table  of  various event counters and memory statistics.  This display
              does not repeat.

       -d, --disk
              Report disk statistics (2.5.70 or above required).

       -D, --disk-sum
              Report some summary statistics about disk activity.

       -p, --partition device
              Detailed statistics about partition (2.5.70 or above required).

       -S, --unit character
              Switches outputs between 1000 (k), 1024 (K), 1000000 (m),  or  1048576  (M)  bytes.
              Note  this  does  not change the block (bi/bo) fields, which are always measured in
              blocks.

       -t, --timestamp
              Append timestamp to each line

       -w, --wide
              Wide output mode (useful for systems with higher amount of memory,  where  the  de-
              fault output mode suffers from unwanted column breakage).  The output is wider than
              80 characters per line.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help and exit.

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

   Memory
       These are affected by the --unit option.
       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
       These are affected by the --unit option.
       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

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

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

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

AUTHORS
       Written by Henry Ware <al172 AT yfn.edu>.
       Fabian Frederick <ffrederick AT users.net> (diskstat, slab, partitions...)

REPORTING BUGS
       Please send bug reports to <procps AT freelists.org>

procps-ng                                 September 2011                                VMSTAT(8)

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