SOLVED: Which I/O Scheduler is in Use?

[Kurt Wall]

On Wednesday 18 May 2005 06:50, David Bandel enlightened us thusly:
> On 5/17/05, Kurt Wall <kwall at kurtwerks.com> wrote:
> > I've been passing elevator=deadline on the kernel command
> > line, but I see no indication that it is actually in use
> > from dmesg for the system log:

[...]

> > How do I find out which I/O scheduler is in use?
>
> david at tole:~$ dmesg | grep scheduler
> Using anticipatory io scheduler

Someone posting to LKML asked exactly the same question,
which produce what appears to be a definitive answer:

$ cat /sys/block/<device>/queue/scheduler

Thus,

$ for file in `find /sys -name scheduler`
> do
> echo -n "$file: "
> cat $file
> done
/sys/block/fd0/queue/scheduler: noop anticipatory [deadline] cfq
/sys/block/hdd/queue/scheduler: noop anticipatory [deadline] cfq
/sys/block/hdc/queue/scheduler: noop anticipatory [deadline] cfq
/sys/block/hdb/queue/scheduler: noop anticipatory [deadline] cfq
/sys/block/hda/queue/scheduler: noop anticipatory [deadline] cfq

The bracketed scheduler is the one in use.

See http://www.uwsg.indiana.edu/hypermail/linux/kernel/0505.3/0562.html

Kurt