linux-kernel - Re: [patch 2/2]block: recursive merge requests

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Date:	Fri, 16 Dec 2011 13:59:07 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Shaohua Li <shaohua.li@...el.com>
CC:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/2]block: recursive merge requests

On 2011-12-16 02:52, Shaohua Li wrote:
> 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%.

Interesting, I didn't consider that corner case. Hard to argue with the
numbers, this might positively impact apps using posix aio for instance.
Applied to for-3.3/core.

-- 
Jens Axboe

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