1===================
2Switching Scheduler
3===================
4
5Each io queue has a set of io scheduler tunables associated with it. These
6tunables control how the io scheduler works. You can find these entries
7in::
8
9	/sys/block/<device>/queue/iosched
10
11assuming that you have sysfs mounted on /sys. If you don't have sysfs mounted,
12you can do so by typing::
13
14	# mount none /sys -t sysfs
15
16It is possible to change the IO scheduler for a given block device on
17the fly to select one of mq-deadline, none, bfq, or kyber schedulers -
18which can improve that device's throughput.
19
20To set a specific scheduler, simply do this::
21
22	echo SCHEDNAME > /sys/block/DEV/queue/scheduler
23
24where SCHEDNAME is the name of a defined IO scheduler, and DEV is the
25device name (hda, hdb, sga, or whatever you happen to have).
26
27The list of defined schedulers can be found by simply doing
28a "cat /sys/block/DEV/queue/scheduler" - the list of valid names
29will be displayed, with the currently selected scheduler in brackets::
30
31  # cat /sys/block/sda/queue/scheduler
32  [mq-deadline] kyber bfq none
33  # echo none >/sys/block/sda/queue/scheduler
34  # cat /sys/block/sda/queue/scheduler
35  [none] mq-deadline kyber bfq
36