To choose IO schedulers at boot time, use the argument 'elevator=deadline'. 'noop' and 'cfq' (the default) are also available. IO schedulers are assigned globally at boot time only presently.
Each io queue has a set of io scheduler tunables associated with it. These tunables control how the io scheduler works. You can find these entries in:
assuming that you have sysfs mounted on /sys. If you don't have sysfs mounted, you can do so by typing:
# mount none /sys -t sysfs
It is possible to change the IO scheduler for a given block device on the fly to select one of mq-deadline, none, bfq, or kyber 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/sda/queue/scheduler [mq-deadline] kyber bfq none # echo none >/sys/block/sda/queue/scheduler # cat /sys/block/sda/queue/scheduler [none] mq-deadline kyber bfq