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Commit 73af994c authored by Valdis Kletnieks's avatar Valdis Kletnieks Committed by Jens Axboe
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[PATCH] Document online io scheduler switching 



We added the ability to change a block device's IO elevator scheduler both
at kernel boot and on-the-fly, but we only documented the elevator= boot
parameter.  Add a quick how-to on doing it on the fly.

Signed-off-by: default avatarValdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 5a7b46b3

Documentation/block/switching-sched.txt

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+22 −0
Original line number Diff line number Diff line 
As of the Linux 2.6.10 kernel, it is now possible to change the

IO scheduler for a given block device on the fly (thus making it possible,

for instance, to set the CFQ scheduler for the system default, but

set a specific device to use the anticipatory or noop schedulers - which

can improve that device's throughput).



To set a specific scheduler, simply do this:



echo SCHEDNAME > /sys/block/DEV/queue/scheduler



where SCHEDNAME is the name of a defined IO scheduler, and DEV is the

device name (hda, hdb, sga, or whatever you happen to have).



The list of defined schedulers can be found by simply doing

a "cat /sys/block/DEV/queue/scheduler" - the list of valid names

will be displayed, with the currently selected scheduler in brackets:



# cat /sys/block/hda/queue/scheduler

noop anticipatory deadline [cfq]

# echo anticipatory > /sys/block/hda/queue/scheduler

# cat /sys/block/hda/queue/scheduler

noop [anticipatory] deadline cfq