man/free.1 - master - githubmirror/procps

man/free.1
171 строка5 KB
Jan Rybar
free manpage: note on negative value with overcommitt enabled
28 окт 2025, 09:37
28 окт 2025, 09:379a8dc78
.\"
.\" Copyright (c) 2011-2023 Craig Small <csmall@dropbear.xyz>
.\" Copyright (c) 2013-2023 Jim Warner <james.warner@comcast.net>
.\" Copyright (c) 2011-2012 Sami Kerola <kerolasa@iki.fi>
.\" Copyright (c) 2002-2003 Albert Cahalan
.\" Copyright (c) 1993      Matt Welsh <mdw@sunsite.unc.edu>
.\"
.\" This program is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\"
.\"
.TH FREE 1 2023-05-02 procps-ng
.SH NAME
free \- Display amount of free and used memory in the system
.SH SYNOPSIS
.B free
.RI [ option " .\|.\|.]"
.SH DESCRIPTION
.B free
displays the total amount of free and used physical and swap memory in the
system, as well as the buffers and caches used by the kernel. The
information is gathered by parsing /proc/meminfo. The displayed
columns are:
.TP
\fBtotal\fR
Total usable memory (MemTotal and SwapTotal in /proc/meminfo). This includes
the physical and swap memory minus a few reserved bits and kernel binary code.
.TP
\fBused\fR
Used or unavailable memory (calculated as \fBtotal\fR - \fBavailable\fR)
.TP
\fBfree\fR
Unused memory (MemFree and SwapFree in /proc/meminfo)
.TP
\fBshared\fR
Memory used (mostly) by tmpfs (Shmem in /proc/meminfo)
.TP
\fBbuffers\fR
Memory used by kernel buffers (Buffers in /proc/meminfo)
.TP
\fBcache\fR
Memory used by the page cache and slabs (Cached and SReclaimable in /proc/meminfo)
.TP
\fBbuff/cache\fR
Sum of \fBbuffers\fR and \fBcache\fR
.TP
\fBavailable\fR
Estimation of how much memory is available for starting
new applications, without swapping. Unlike the data
provided by the \fBcache\fR or \fBfree\fR fields,
this field takes into account page cache and also that
not all reclaimable memory slabs will be reclaimed
due to items being in use (MemAvailable in /proc/meminfo, available on
kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as \fBfree\fR)
.SH OPTIONS
.TP
\fB\-b\fR, \fB\-\-bytes\fR
Display the amount of memory in bytes.
.TP
\fB\-k\fR, \fB\-\-kibi\fR
Display the amount of memory in kibibytes.  This is the default.
.TP
\fB\-m\fR, \fB\-\-mebi\fR
Display the amount of memory in mebibytes.
.TP
\fB\-g\fR, \fB\-\-gibi\fR
Display the amount of memory in gibibytes.
.TP
\fB\-\-tebi\fR
Display the amount of memory in tebibytes.
.TP
\fB\-\-pebi\fR
Display the amount of memory in pebibytes.
.TP
\fB\-\-kilo\fR
Display the amount of memory in kilobytes. Implies --si.
.TP
\fB\-\-mega\fR
Display the amount of memory in megabytes. Implies --si.
.TP
\fB\-\-giga\fR
Display the amount of memory in gigabytes. Implies --si.
.TP
\fB\-\-tera\fR
Display the amount of memory in terabytes. Implies --si.
.TP
\fB\-\-peta\fR
Display the amount of memory in petabytes. Implies --si.
.TP
\fB\-h\fR, \fB\-\-human\fP
Show all output fields automatically scaled to shortest three digit unit and
display the units of print out.  Following units are used.
.sp
.nf
  B = bytes
  Ki = kibibyte
  Mi = mebibyte
  Gi = gibibyte
  Ti = tebibyte
  Pi = pebibyte
.fi
.sp
If unit is missing, and you have exbibyte of RAM or swap, the number is in
tebibytes and columns might not be aligned with header.
.TP
\fB\-w\fR, \fB\-\-wide\fR
Switch to the wide mode. The wide mode produces lines longer
than 80 characters. In this mode \fBbuffers\fR and \fBcache\fR
are reported in two separate columns.
.TP
\fB\-c\fR, \fB\-\-count\fR \fIcount\fR
Display the result
.I count
times.  Requires the
.B \-s
option.
.TP
\fB\-l\fR, \fB\-\-lohi\fR
Show detailed low and high memory statistics.
.TP
\fB\-L\fR, \fB\-\-line\fR
Show output on a single line, often used with the
.B \-s
option to show memory statistics repeatedly.
.TP
\fB\-s\fR, \fB\-\-seconds\fR \fIdelay\fR
Continuously display the result \fIdelay\fR  seconds
apart.  You may actually specify any floating point number for
\fIdelay\fR using either . or , for decimal point.
.BR usleep (3)
is used for microsecond resolution delay times.
.TP
\fB\-\-si\fR
Use kilo, mega, giga etc (power of 1000) instead of kibi, mebi, gibi (power
of 1024).
.TP
\fB\-t\fR, \fB\-\-total\fR
Display a line showing the column totals.
.TP
\fB\-v\fR, \fB\-\-committed\fR
Display a line showing the memory commit limit and amount of committed/uncommitted
memory. The \fBtotal\fR column on this line will display the memory commit
limit.   This line is relevant if memory overcommit is disabled.   On systems
with memory overcommit enabled, the \fBfree\fR value can temporarily appear
negative. This is not a bug, but an effect of overcommit, as the system has promised
more memory than the total of its virtual address space.
The negative value indicates the magnitude of the system's memory over-allocation.
.TP
\fB\-\-help\fR
Print help.
.TP
\fB\-V\fR, \fB\-\-version\fR
Display version information.
.SH FILES
.TP
/proc/meminfo
memory information
.SH BUGS
The value for the \fBshared\fR column is not available from kernels before
2.6.32 and is displayed as zero.
.P
Please send bug reports to
.MT procps@freelists.org
.ME .
.SH "SEE ALSO"
.BR ps (1),
.BR slabtop (1),
.BR top "(1),
.BR vmstat (8).