linux-kernel - Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed

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Date:	Sun, 6 Dec 2009 11:49:50 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Corrado Zoccolo <czoccolo@...il.com>
Cc:	Linux-Kernel <linux-kernel@...r.kernel.org>,
	Jeff Moyer <jmoyer@...hat.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH] cfq-iosched: reduce write depth only if sync was
	delayed

On Sun, Dec 06 2009, Corrado Zoccolo wrote:
> Hi Jeff,
> I remember you saw large performance drop on your SAN for sequential
> writes with low_latency=1.  Can you test if Shaohua's and this patch
> fix allow to recover some bandwidth?  I think that enabling the queue
> depth ramp up only if a sync request was delayed should disable it for
> fast hardware like yours, so you should not be seeing the slowdown any
> more.

I queued this up for post inclusion into 2.6.33, with the time_after()
fixed.

The patch was word-wrapped, btw.

-- 
Jens Axboe

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