nbd: increase default and max request sizes
authorMichal Belczyk <belczyk@bsd.krakow.pl>
Tue, 30 Apr 2013 22:28:28 +0000 (15:28 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 1 May 2013 00:04:07 +0000 (17:04 -0700)
commit078be02b80359a541928c899c2631f39628f56df
treeb89690216b6c55b91d9d14775592b660c69010cf
parent5cc5445164c16d32bab2912fac28356ab07aa8b4
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>
drivers/block/nbd.c