The patch titled NBD: make nbd default to deadline I/O scheduler has been added to the -mm tree. Its filename is nbd-make-nbd-default-to-deadline-i-o-scheduler.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: NBD: make nbd default to deadline I/O scheduler From: Paul Clements <paul.clements@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> Cc: Jens Axboe <jens.axboe@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/block/nbd.c | 6 ++++++ 1 file changed, 6 insertions(+) diff -puN drivers/block/nbd.c~nbd-make-nbd-default-to-deadline-i-o-scheduler drivers/block/nbd.c --- a/drivers/block/nbd.c~nbd-make-nbd-default-to-deadline-i-o-scheduler +++ a/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")) { _ Patches currently in -mm which might be from paul.clements@xxxxxxxxxxxx are origin.patch nbd-make-nbd-default-to-deadline-i-o-scheduler.patch - To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html