Commit 078be02b authored Apr 30, 2013 by Michal Belczyk Committed by Linus Torvalds Apr 30, 2013

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>

parent 5cc54451

drivers/block/nbd.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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")) {

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