From: Shaohua Li <shaohua.li@intel.com>
Date: Fri, 16 Dec 2011 13:00:31 +0000 (+0100)
Subject: block: recursive merge requests
X-Git-Tag: v3.3-rc1~49^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=274193224cdabd687d804a26e0150bb20f2dd52c;p=pandora-kernel.git

block: recursive merge requests

In my workload, thread 1 accesses a, a+2, ..., thread 2 accesses a+1,
a+3,.... When the requests are flushed to queue, a and a+1 are merged
to (a, a+1), a+2 and a+3 too to (a+2, a+3), but (a, a+1) and (a+2, a+3)
aren't merged.
With recursive merge below, the workload throughput gets improved 20%
and context switch drops 60%.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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