dynamic_pager(8) BSD System Manager's Manual dynamic_pager(8)NAME
dynamic_pager -- external storage manager for dynamic pager
SYNOPSIS
dynamic_pager [-F filename] [-S filesize] [-H high-water-trigger] [-L low-water-trigger] [-P priority]
DESCRIPTION
The dynamic_pager daemon manages a pool of external swap files which the kernel uses to support demand paging. This pool is expanded with
new swap files as load on the system increases. It is contracted when the swapping resources are no longer needed. The dynamic_pager daemon
also provides a notification service for those applications which wish to receive notices when the external paging pool expands or contracts.
OPTIONS -F The base name of the filename to use for the external paging files. By default this is /private/var/vm/swapfile.
-H If there are less than high-water-trigger bytes free in the external paging files, the kernel will signal dynamic_pager to add a new
external paging file.
-L If there are more than low-water-trigger bytes free in the external paging files, the kernel will coalese in-use pages and signal
dynamic_pager to discard an external paging file. Low-water-trigger must be greater than high-water-trigger + filesize.
-P This option is currently unimplemented.
-S The fixed filesize [in bytes] to use for the paging files. By default dynamic_pager uses variable sized paging files, using larger
sized files as paging demands increase. The -S, -H and -L options disable that default and cause dynamic_pager to use a series of
fixed sized external paging files.
FILES
/private/var/vm/swapfile* Default external paging files.
/Library/Preferences/com.apple.virtualMemory.plist Configuration file.
XML PROPERTY LIST KEYS
The following keys can be specified in the configuration file. Please see plist(5) for more information about property list files.
UseEncryptedSwap <boolean>
This optional key activates encrypted swap (aka Secure VM), so that all data is encrypted before being written to a swap file. The default
is on for portable computers and off for other computers.
Mac OS X July 8, 2003 Mac OS X
Check Out this Related Man Page
SWAPON(8) Linux Programmer's Manual SWAPON(8)NAME
swapon, swapoff - enable/disable devices and files for paging and swapping
SYNOPSIS
Get info:
swapon -s [-h] [-V]
Enable/disable:
swapon [-f] [-p priority] [-v] specialfile...
swapoff [-v] specialfile...
Enable/disable all:
swapon -a [-e] [-f] [-v]
swapoff -a [-v]
DESCRIPTION
swapon is used to specify devices on which paging and swapping are to take place.
The device or file used is given by the specialfile parameter. It may be of the form -L label or -U uuid to indicate a device by label or
uuid.
Calls to swapon normally occur in the system boot scripts making all swap devices available, so that the paging and swapping activity is
interleaved across several devices and files.
swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices
and files (as found in /proc/swaps or /etc/fstab).
-a, --all
All devices marked as ``swap'' in /etc/fstab are made available, except for those with the ``noauto'' option. Devices that are
already being used as swap are silently skipped.
-e, --ifexists
Silently skip devices that do not exist.
-f, --fixpgsz
Reinitialize (exec /sbin/mkswap) the swap space if its page size does not match that of the the current running kernel. mkswap(2)
initializes the whole device and does not check for bad blocks.
-h, --help
Provide help.
-L label
Use the partition that has the specified label. (For this, access to /proc/partitions is needed.)
-p, --priority priority
Specify the priority of the swap device. priority is a value between 0 and 32767. Higher numbers indicate higher priority. See
swapon(2) for a full description of swap priorities. Add pri=value to the option field of /etc/fstab for use with swapon -a.
-s, --summary
Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25.
-U uuid
Use the partition that has the specified uuid.
-v, --verbose
Be verbose.
-V, --version
Display version.
NOTES
You should not use swapon on a file with holes. Swap over NFS may not work.
swapon automatically detects and rewrites swap space signature with old software suspend data (e.g S1SUSPEND, S2SUSPEND, ...). The problem
is that if we don't do it, then we get data corruption the next time an attempt at unsuspending is made.
swapon may not work correctly when using a swap file with some versions of btrfs. This is due to the swap file implementation in the ker-
nel expecting to be able to write to the file directly, without the assistance of the file system. Since btrfs is a copy-on-write file
system, the file location may not be static and corruption can result. Btrfs actively disallows the use of files on its file systems by
refusing to map the file. This can be seen in the system log as "swapon: swapfile has holes." One possible workaround is to map the file to
a loopback device. This will allow the file system to determine the mapping properly but may come with a performance impact.
SEE ALSO swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8)FILES
/dev/sd?? standard paging devices
/etc/fstab ascii filesystem description table
HISTORY
The swapon command appeared in 4.0BSD.
AVAILABILITY
The swapon command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
Linux 1.x 25 September 1995 SWAPON(8)