From: Shaohua Li <shli@kernel.org>
Date: Wed, 9 Apr 2014 03:25:47 +0000 (+0800)
Subject: raid5: make_request does less prepare wait
X-Git-Tag: v3.15-rc1~20^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=27c0f68f0745218cec70f19ba7560c8c5fc3f817;p=pandora-kernel.git

raid5: make_request does less prepare wait

In NUMA machine, prepare_to_wait/finish_wait in make_request exposes a
lot of contention for sequential workload (or big request size
workload). For such workload, each bio includes several stripes. So we
can just do prepare_to_wait/finish_wait once for the whold bio instead
of every stripe.  This reduces the lock contention completely for such
workload. Random workload might have the similar lock contention too,
but I didn't see it yet, maybe because my stroage is still not fast
enough.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
---

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