NBD: make nbd default to deadline I/O scheduler

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 <[email protected]>
Cc: Jens Axboe <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions