nbd: increase default and max request sizes

Raise the default max request size for nbd to 128KB (from 127KB) to get it
4KB aligned.  This patch also allows the max request size to be increased
(via /sys/block/nbd<x>/queue/max_sectors_kb) to 32MB.

The patch makes nbd network traffic more efficient by:
- reducing request fragmentation (4KB alignment)
- reducing the number of requests (fewer round trips, less network overhead)

Especially in high latency networks, larger request size can make a dramatic

Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Michal Belczyk <belczyk@bsd.krakow.pl>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michal Belczyk 2013-04-30 15:28:28 -07:00 committed by Linus Torvalds
parent 5cc5445164
commit 078be02b80

View File

@ -856,6 +856,8 @@ static int __init nbd_init(void)
disk->queue->limits.discard_granularity = 512;
disk->queue->limits.max_discard_sectors = UINT_MAX;
disk->queue->limits.discard_zeroes_data = 0;
blk_queue_max_hw_sectors(disk->queue, 65536);
disk->queue->limits.max_sectors = 256;
}
if (register_blkdev(NBD_MAJOR, "nbd")) {