Based on kernel version 3.15.4. Page generated on 2014-07-07 09:00 EST.
1 To choose IO schedulers at boot time, use the argument 'elevator=deadline'. 2 'noop' and 'cfq' (the default) are also available. IO schedulers are assigned 3 globally at boot time only presently. 4 5 Each io queue has a set of io scheduler tunables associated with it. These 6 tunables control how the io scheduler works. You can find these entries 7 in: 8 9 /sys/block/<device>/queue/iosched 10 11 assuming that you have sysfs mounted on /sys. If you don't have sysfs mounted, 12 you can do so by typing: 13 14 # mount none /sys -t sysfs 15 16 As of the Linux 2.6.10 kernel, it is now possible to change the 17 IO scheduler for a given block device on the fly (thus making it possible, 18 for instance, to set the CFQ scheduler for the system default, but 19 set a specific device to use the deadline or noop schedulers - which 20 can improve that device's throughput). 21 22 To set a specific scheduler, simply do this: 23 24 echo SCHEDNAME > /sys/block/DEV/queue/scheduler 25 26 where SCHEDNAME is the name of a defined IO scheduler, and DEV is the 27 device name (hda, hdb, sga, or whatever you happen to have). 28 29 The list of defined schedulers can be found by simply doing 30 a "cat /sys/block/DEV/queue/scheduler" - the list of valid names 31 will be displayed, with the currently selected scheduler in brackets: 32 33 # cat /sys/block/hda/queue/scheduler 34 noop deadline [cfq] 35 # echo deadline > /sys/block/hda/queue/scheduler 36 # cat /sys/block/hda/queue/scheduler 37 noop [deadline] cfq