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authorValdis Kletnieks <valdis.kletnieks@vt.edu>2006-04-19 03:23:09 -0400
committerJens Axboe <axboe@nelson.home.kernel.dk>2006-04-20 07:04:36 -0400
commit73af994c7d58dd513922dc9d5cd76b124ec02b1b (patch)
tree793dfd57372a73a5c4b1e7c8b9f33a04fc08b61e /Documentation/block
parent5a7b46b369419493bab4de67b1526e9f76b22a7f (diff)
[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: Valdis Kletnieks <valdis.kletnieks@vt.edu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Jens Axboe <axboe@suse.de>
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1As of the Linux 2.6.10 kernel, it is now possible to change the
2IO scheduler for a given block device on the fly (thus making it possible,
3for instance, to set the CFQ scheduler for the system default, but
4set a specific device to use the anticipatory or noop schedulers - which
5can improve that device's throughput).
6
7To set a specific scheduler, simply do this:
8
9echo SCHEDNAME > /sys/block/DEV/queue/scheduler
10
11where SCHEDNAME is the name of a defined IO scheduler, and DEV is the
12device name (hda, hdb, sga, or whatever you happen to have).
13
14The list of defined schedulers can be found by simply doing
15a "cat /sys/block/DEV/queue/scheduler" - the list of valid names
16will be displayed, with the currently selected scheduler in brackets:
17
18# cat /sys/block/hda/queue/scheduler
19noop anticipatory deadline [cfq]
20# echo anticipatory > /sys/block/hda/queue/scheduler
21# cat /sys/block/hda/queue/scheduler
22noop [anticipatory] deadline cfq