+++ /dev/null
-.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" Modified by Michael Haardt <michael@moria.de>
-.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
-.\" Modified 1995-07-22 by Michael Chastain <mec@duracef.shout.net>
-.\" Modified 1995-07-23 by aeb
-.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
-.\" Modified 1998-09-08 by aeb
-.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" Modified 2004-10-10 by aeb
-.\" 2004-12-14 mtk, Anand Kumria: added new errors
-.\" 2007-06-22 Ivana Varekova <varekova@redhat.com>, mtk
-.\" Update text describing limit on number of swap files.
-.\"
-.\" FIXME Linux 3.11 added SWAP_FLAG_DISCARD_ONCE and SWAP_FLAG_DISCARD_PAGES
-.\" commit dcf6b7ddd7df8965727746f89c59229b23180e5a
-.\" Author: Rafael Aquini <aquini@redhat.com>
-.\" Date: Wed Jul 3 15:02:46 2013 -0700
-.\"
-.TH SWAPON 2 2014-05-28 "Linux" "Linux Programmer's Manual"
-.SH NAME
-swapon, swapoff \- start/stop swapping to file/device
-.SH SYNOPSIS
-.B #include <unistd.h>
-.br
-.B #include <sys/swap.h>
-.sp
-.BI "int swapon(const char *" path ", int " swapflags );
-.br
-.BI "int swapoff(const char *" path );
-.SH DESCRIPTION
-.BR swapon ()
-sets the swap area to the file or block device specified by
-.IR path .
-.BR swapoff ()
-stops swapping to the file or block device specified by
-.IR path .
-.PP
-If the
-.B SWAP_FLAG_PREFER
-flag is specified in the
-.BR swapon ()
-.I swapflags
-argument, the new swap area will have a higher priority than default.
-The priority is encoded within
-.I swapflags
-as:
-.br
-.sp
-.I " (prio << SWAP_FLAG_PRIO_SHIFT) & SWAP_FLAG_PRIO_MASK"
-.br
-.PP
-If the
-.B SWAP_FLAG_DISCARD
-flag is specified in the
-.BR swapon ()
-.I swapflags
-argument, freed swap pages will be discarded before they are reused,
-if the swap device supports the discard or trim operation.
-(This may improve performance on some Solid State Devices,
-but often it does not.)
-See also NOTES.
-.PP
-These functions may be used only by a privileged process (one having the
-.B CAP_SYS_ADMIN
-capability).
-.SS Priority
-Each swap area has a priority, either high or low.
-The default priority is low.
-Within the low-priority areas,
-newer areas are even lower priority than older areas.
-.PP
-All priorities set with
-.I swapflags
-are high-priority, higher than default.
-They may have any nonnegative value chosen by the caller.
-Higher numbers mean higher priority.
-.PP
-Swap pages are allocated from areas in priority order,
-highest priority first.
-For areas with different priorities,
-a higher-priority area is exhausted before using a lower-priority area.
-If two or more areas have the same priority,
-and it is the highest priority available,
-pages are allocated on a round-robin basis between them.
-.PP
-As of Linux 1.3.6, the kernel usually follows these rules,
-but there are exceptions.
-.SH RETURN VALUE
-On success, zero is returned.
-On error, \-1 is returned, and
-.I errno
-is set appropriately.
-.SH ERRORS
-.TP
-.B EBUSY
-(for
-.BR swapon ())
-The specified
-.I path
-is already being used as a swap area.
-.TP
-.B EINVAL
-The file
-.I path
-exists, but refers neither to a regular file nor to a block device;
-.TP
-.B EINVAL
-.RB ( swapon ())
-The indicated path does not contain a valid swap signature or
-resides on an in-memory filesystem such as tmpfs.
-.TP
-.BR EINVAL " (since Linux 3.4)"
-.RB ( swapon ())
-An invalid flag value was specified in
-.IR flags .
-.TP
-.B EINVAL
-.RB ( swapoff ())
-.I path
-is not currently a swap area.
-.TP
-.B ENFILE
-The system limit on the total number of open files has been reached.
-.TP
-.B ENOENT
-The file
-.I path
-does not exist.
-.TP
-.B ENOMEM
-The system has insufficient memory to start swapping.
-.TP
-.B EPERM
-The caller does not have the
-.B CAP_SYS_ADMIN
-capability.
-Alternatively, the maximum number of swap files are already in use;
-see NOTES below.
-.SH CONFORMING TO
-These functions are Linux-specific and should not be used in programs
-intended to be portable.
-The second
-.I swapflags
-argument was introduced in Linux 1.3.2.
-.SH NOTES
-The partition or path must be prepared with
-.BR mkswap (8).
-
-There is an upper limit on the number of swap files that may be used,
-defined by the kernel constant
-.BR MAX_SWAPFILES .
-Before kernel 2.4.10,
-.B MAX_SWAPFILES
-has the value 8;
-since kernel 2.4.10, it has the value 32.
-Since kernel 2.6.18, the limit is decreased by 2 (thus: 30)
-if the kernel is built with the
-.B CONFIG_MIGRATION
-option
-(which reserves two swap table entries for the page migration features of
-.BR mbind (2)
-and
-.BR migrate_pages (2)).
-Since kernel 2.6.32, the limit is further decreased by 1
-if the kernel is built with the
-.B CONFIG_MEMORY_FAILURE
-option.
-
-Discard of swap pages was introduced in kernel 2.6.29,
-then made conditional
-on the
-.B SWAP_FLAG_DISCARD
-flag in kernel 2.6.36,
-.\" To be precise: 2.6.35.5
-which still discards the
-entire swap area when
-.BR swapon ()
-is called, even if that flag bit is not set.
-.SH SEE ALSO
-.BR mkswap (8),
-.BR swapoff (8),
-.BR swapon (8)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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