[PATCH] Document online io scheduler switching

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