diff options
| author | Paul Clements <paul.clements@steeleye.com> | 2008-02-23 15:23:50 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-23 17:12:15 -0800 |
| commit | 48f15b93b2c9f4ec9b8af08ab78f7a27db7c8378 (patch) | |
| tree | 8fc5a20c743fe7e223502a08b9b15d31912ef7de | |
| parent | 2f56debd77a8f52f1ac1d3c3d89cc7ce5e083230 (diff) | |
| download | lwn-48f15b93b2c9f4ec9b8af08ab78f7a27db7c8378.tar.gz lwn-48f15b93b2c9f4ec9b8af08ab78f7a27db7c8378.zip | |
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 <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>
| -rw-r--r-- | drivers/block/nbd.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 018753c59b8e..b53fdb0a282c 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -655,6 +655,7 @@ static int __init nbd_init(void) for (i = 0; i < nbds_max; i++) { struct gendisk *disk = alloc_disk(1); + elevator_t *old_e; if (!disk) goto out; nbd_dev[i].disk = disk; @@ -668,6 +669,11 @@ static int __init nbd_init(void) put_disk(disk); goto out; } + old_e = disk->queue->elevator; + if (elevator_init(disk->queue, "deadline") == 0 || + elevator_init(disk->queue, "noop") == 0) { + elevator_exit(old_e); + } } if (register_blkdev(NBD_MAJOR, "nbd")) { |