20ece57af8
- added support for start and stop options to profile scripts calls - fixed CMDLINE_ELEVATOR test (rhbz#496940#c9) - new README.ktune
141 lines
5 KiB
Text
141 lines
5 KiB
Text
ktune
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===============================================================================
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This description will give you a quick overview of ktune and what it can do for
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you.
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1) What is ktune?
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2) What it does
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2.1) ktune start
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2.2) ktune stop
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3) How you can use it
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4) How you can extend it
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5) Planned features
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1) What is ktune?
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-------------------------------------------------------------------------------
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The kernel in a Linux system is configured to fit the needs of a lot of
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customers and use cases. But for certain use cases these defaults might not be
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appropriate. For example there are use cases where much more shared memory
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segments are needed as with others. Also the size of network buffers might be
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important and also the elevator used for block devices to get maximum
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performance.
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Initially the service ktune was created to have a simple way to tune kernel
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parameters according to a usage profile. Over time this service has been
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expanded to support multiple profiles and provide more than kernel parameter
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tuning as well as adding a way for customers to use their own tuning settings.
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The package ktune provides a service init script together with a global config
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file and a sysctl throughput settings file, a directory to store additional
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profiles and some documentation.
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/etc/rc.d/init.d/ktune
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/etc/sysconfig/ktune
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/etc/sysctl.ktune
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/etc/ktune.d/
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/usr/share/doc/ktune-0.4
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/usr/share/doc/ktune-0.4/COPYING
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/usr/share/doc/ktune-0.4/README
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2) What it does
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-------------------------------------------------------------------------------
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ktune is a system service that is primarily managed by chkconfig. If the
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service is enabled and started, it will use the configuration options from
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/etc/sysconfig/ktune:
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SYSCTL="/etc/sysctl.ktune"
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USE_KTUNE_D="yes"
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SYSCTL_POST="/etc/sysctl.conf"
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ELEVATOR="deadline"
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ELEVATOR_TUNE_DEVS="/sys/block/{sd,cciss}*/queue/scheduler"
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SYSCTL is the primary ktune sysctl profile. If you comment it out, it will not
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get applied.
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USE_KTUNE_D is a switch, that enables or disabled the use of additional
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profiles from the /etc/ktune.d directory. A profile has to have the extension
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.conf to be used. If there is an additional file with the same name, but the
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extension .sh it will be used as a profile script.
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SYSCTL_POST references the system wide sysctl file for customer settings.
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ELEVATOR is the I/O scheduler, ktune will set for ELEVATOR_TUNE_DEVS. If you
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want to disable the setting of the I/O scheduler, just comment out the ELEVATOR
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line. ktune will not apply any scheduler if a scheduler is set on the kernel
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command line. It is safe to leave this on "deadline", but "as", "cfq", and
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"noop" are also legal values. ELEVATOR_TUNE_DEVS references the devices which
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should be tuned with the ELEVATOR.
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2.1) ktune start
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When the service starts, it is applying the sysctl settings from the SYSCTL
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file and afterwards the sysctl settings from the conf files in the /etc/ktune.d
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directory. For each sysctl settings, that will be modified, it will store the
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original value in a save file to be able to restore the initial settings if the
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service is stopped. This way it can easily be evaluated if settings are good or
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bad for a specific environment. After a profile from the ktune.d directory has
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been applied, the profile script will be called if available. The script will
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get the service parameter, the service has been started with: If "service ktune
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start" has been used, profile scripts will be called with the parameter
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"start". This way custom settings, for which the sysctl settings file can not
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be used, can be made.
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After applying the sysctl settings, the elevators will be set.
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2.2) ktune stop
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When the service stopps, it applies the settings saved while starting.
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3) How you can use it
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-------------------------------------------------------------------------------
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The service is managed by chkconfig and can be enabled or disabled for
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automatic system start and stop. If you want to evaluate settings or want to
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find te best settings for your system it is save to leave the service disabled
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and to start or stop it manually with the service command.
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To start or stop ktune you can use the service command:
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service ktune <start|stop>
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To enable or disable ktune for automatic system start, use the chkconfig
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command:
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chkconfig ktune <on|off>
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4) How you can extend it
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-------------------------------------------------------------------------------
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To change the primary profile, use the SYSCTL variable in the ktune sysconfig
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file. If you want to add additional profiles, put them into the /etc/ktune.d
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directory altogether with a profile scrip if needed.
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Skeleton of a profile scipt:
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#!/bin/sh
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case "$1" in
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start)
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# do something
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RETVAL=$?
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;;
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stop)
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# do something
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RETVAL=$?
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;;
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*)
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echo $"Usage: $0 {start|stop}"
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RETVAL=2
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;;
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esac
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exit $RETVAL
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5) Planned features
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-------------------------------------------------------------------------------
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* Readahead tuning for block devices
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