swapd(8)
NAME
swapd - dynamic swapping manager
SYNOPSIS
swapd [-h] [--help] [--copyright] [--config file] [--maxswaps n] [--memlimit kb] [--mkswap path] [--pause msec] [--pidfile file] [--swapdir dir] [--swapsize kb] [--timeout sec]
DESCRIPTION
- swapd is a dynamic swapping manager. It provides the sys
- tem with as much swap space (virtual memory) as is required at a
- particular time by dynamicly creating swap files. This is more
- convinient than using fixed swap files and/or partitions because
- they (a) are unused most of the time and are just taking up disk
- space; and (b) provide a limited amount of virtual memory.
OPTIONS
- All values given on the command line will override config
- file values.
- -h, --help Displays the command line help.
- --copyright Displays the copyright notice.
- --config file Location of an alternate configuration
- file.
- --maxswaps n Maximum number of swap files. No more than
- n swap files will be used. The default is 8 (as many as the de
- fault kernel will allow).
- --memlimit kb Memory limit in kilobytes. When the total
- amount of free memory gets below this number, swapd creates a new
- swap file.
- --mkswap path Location of mkswap(8), usually /sbin/mk
- swap.
- --pause msec Pause between memory checks in miliseconds
- (when the total amount of free memory is above memlimit).
- --pidfile file Location of the PID file, usually
- /var/run/swapd.pid.
- --swapdir dir Swap directory where all the swap files
- are kept.
- --swapsize kb Swap file size (>=64k).
- --timeout sec Timeout. If the last created swap file is
- unused for sec seconds, it will be removed. The last created
- swapfile is considered unused when there are more than memlimit +
- swapsize kb of free memory (physical + swap).
CONFIGURATION
This is an example configuration file:
# swapd.conf - config file for swapd
#
# Copyright 2000 Neven Lovric <nlovric@jagor.srce.hr>
#
- # Memory limit in kilobytes.
# When the total amount of free memory gets below this - number, swapd creates
# a new swap file.
# 16384 or more recommended
memlimit 16384 - # Pause between memory checks in miliseconds.
# When the total amount of free memory is above <memlim - it>, swapd will pause
# for <pause> miliseconds before checking memory again.
# 1000 should be ok for most systems
pause 1000 - # Swap file size in kilobytes.
# >= 64, 4096 recommended
swapsize 4096 - # Maximum number of swap files.
# No more than <maxswaps> swap files will be used.
# 0 = unlimited (as many as the kernel will allow)
# 8 = how many a default kernel allows
maxswaps 8 - # Timeout in seconds.
# If the last created swap file is unused for <sec> sec - onds, it will be
# removed. The last created swapfile is considered unused - when there are
# more than <memlimit> + <swapsize> kb of free memory - (physical + swap).
# 60 is nice
timeout 60 - # Swap directory where all the swap files are kept.
swapdir /swap - # PID file (where the currently running swapd stores it's
- PID so a new swapd
# can find it)
pidfile /var/run/swapd.pid - # Full path to mkswap.
mkswap /sbin/mkswap
PERFORMANCE
- The most important parameter which may drasticly effect
- performance is the memory limit. If the memory limit is low, (1)
- there may not be enough memory ready for a program to allocate at
- once or (2) swapd may not be able to create new swap files before
- we run out of memory. If your programs are running out of memory,
- it will primarily be due to a low memory limit. If you really
- want to have a low memory limit, you should decrease the swap
- size and pause.
- The second important parameter is the swap size. If you
- choose to use bigger swap files, you may experience slowdowns
- when swap files are created. On the other hand, small swap files
- may lower performance when there are many of them. The important
- thing is not to make them too big to create before we run out of
- memory.
- Another important parameter is the pause, which should be
- shorter on faster systems. If it is too long, swapd may fail to
- detect rapid memory changes and therefore fail to create new swap
- files when they are needed. However, if you notice swapd is con
- stantly using too much CPU, increase the pause.
FILES
/etc/swapd.conf
/var/run/swapd.pid
/etc/init.d/swapd
SWAPDIR/linux*.swp
BUGS
Might fail if swapping over NFS
SEE ALSO
mkswap(8), swapon(8), swapoff(8), free(8)
MAINTAINER
Aigars Mahinovs <aigarius@debian.org>
AUTHOR
Neven Lovric <nlovric@linux.hr>
- The latest upstream version is available via anonymous
- ftp:
ftp://ftp.linux.hr/pub/swapd- swapd May 21, 2000