From: Shaohua Li <shli@fusionio.com>
Date: Fri, 9 Nov 2012 07:44:27 +0000 (+0100)
Subject: block: recursive merge requests
X-Git-Tag: v3.8-rc1~81^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bee0393cc12b6d8f10e884e555a095e050e0b2b9;p=pandora-kernel.git

block: recursive merge requests

In a 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.

If we do recursive merge for such interleave access, some workloads throughput
get improvement. A recent worload I'm checking on is swap, below change
boostes the throughput around 5% ~ 10%.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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