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authorValdis Kletnieks <valdis.kletnieks@vt.edu>2006-04-19 09:23:09 +0200
committerJens Axboe <axboe@nelson.home.kernel.dk>2006-04-20 13:04:36 +0200
commit73af994c7d58dd513922dc9d5cd76b124ec02b1b (patch)
tree793dfd57372a73a5c4b1e7c8b9f33a04fc08b61e /Documentation/block
parent5a7b46b369419493bab4de67b1526e9f76b22a7f (diff)
downloadlinux-linaro-stable-73af994c7d58dd513922dc9d5cd76b124ec02b1b.tar.gz
[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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+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