procps/vmstat.8

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.\" This page Copyright (C) 1994 Henry Ware <al172@yfn.ysu.edu>
.\" Distributed under the GPL, Copyleft 1994.
.TH VMSTAT 8 "27 July 1994 " "Throatwobbler Ginkgo Labs" "Linux Administrator's Manual"
.SH NAME
vmstat \- Report virtual memory statistics
.SH SYNOPSIS
.ft B
.B vmstat
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.RB [ "\-a" ]
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.RB [ "\-n" ]
.RI [ delay " [ " count ]]
.br
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.B vmstat
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.RB [ "\-f" ]
.RB [ "\-s" ]
.br
.B vmstat
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.RB [ "\-S unit"]
.br
.B vmstat
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.RB [ "\-V" ]
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.SH DESCRIPTION
\fBvmstat\fP reports information about processes, memory, paging,
block IO, traps, and cpu activity.
The first report produced gives averages since the last reboot. Additional
reports give information on a sampling period of length \fIdelay\fP.
The process and memory reports are instantaneous in either case.
.SS Options
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The \fB-a\fP switch displays active/inactive memory, given a 2.5.41 kernel or better.
.PP
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The \fB-f\fP 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.
.PP
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The \fB-n\fP switch causes the header to be displayed only once rather than periodically.
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.PP
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The \fB-s\fP switch displays a table of various event counters
and memory statistics. This display does not repeat.
.PP
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.I delay
is the delay between updates in seconds. If no delay is specified,
only one report is printed with the average values since boot.
.PP
.I count
is the number of updates. If no count is specified and delay is
defined, \fIcount\fP defaults to infinity.
.PP
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The \fB-S\fP followed by k or K or m or M switches outputs between 1000, 1024, 1000000, or 1048576 bytes
.PP
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The \fB-V\fP switch results in displaying version information.
.PP
.SH FIELD DESCRIPTIONS
.SS
.B "Procs"
.nf
r: The number of processes waiting for run time.
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b: The number of processes in uninterruptible sleep.
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.fi
.PP
.SS
.B "Memory"
.nf
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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)
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.fi
.PP
.SS
.B "Swap"
.nf
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si: Amount of memory swapped in from disk (/s).
so: Amount of memory swapped to disk (/s).
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.fi
.PP
.SS
.B "IO"
.nf
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bi: Blocks received from a block device (blocks/s).
bo: Blocks sent to a block device (blocks/s).
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.fi
.PP
.SS
.B "System"
.nf
in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.
.if
.PP
.SS
.B "CPU "
These are percentages of total CPU time.
.nf
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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, shown as zero.
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.nf
.SH NOTES
.B "vmstat "
does not require special permissions.
.PP
These reports are intended to help identify system bottlenecks. Linux
.B "vmstat "
does not count itself as a running process.
.PP
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All linux blocks are currently 1024 bytes. Old kernels may report
blocks as 512 bytes, 2048 bytes, or 4096 bytes.
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.PP
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Since procps 3.1.9, vmstat lets you choose units (k, K, m, M)
.PP
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.SH FILES
.ta
.nf
/proc/meminfo
/proc/stat
/proc/*/stat
.fi
.SH "SEE ALSO"
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iostat(1), sar(1), mpstat(1), ps(1), top(1), free(1)
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.PP
.SH BUGS
Does not tabulate the block io per device or count the number of system calls.
.SH AUTHOR
Written by Henry Ware <al172@yfn.ysu.edu>.