NBD doesn't work well with CFQ (or AS) schedulers, so let's default to
something else.
The two problems I have experienced with nbd and cfq are:
1) nbd hangs with cfq on RHEL 5 (2.6.18) -- this may well have been
fixed
There's a similar debian bug that has been filed as well:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=447638
There have been posts to nbd-general mailing list about problems with
cfq and nbd also.
2) nbd performs about 10% better (the last time I tested) with deadline
vs. cfq (the overhead of cfq doesn't provide much advantage to nbd [not
being a real disk], and you end up going through the I/O scheduler on
the nbd server anyway, so it makes sense that deadline is better with
nbd)
Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
48f15b93b2