linux-kernel - Re: [PATCH 02/20] blkio: Change CFQ to use CFS like queue time stamps

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Date:	Wed, 4 Nov 2009 18:22:16 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Corrado Zoccolo <czoccolo@...il.com>
Cc:	linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	ryov@...inux.co.jp, fernando@....ntt.co.jp, s-uchida@...jp.nec.com,
	taka@...inux.co.jp, guijianfeng@...fujitsu.com, jmoyer@...hat.com,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, akpm@...ux-foundation.org, riel@...hat.com,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH 02/20] blkio: Change CFQ to use CFS like queue time
	stamps

On Wed, Nov 04, 2009 at 10:18:15PM +0100, Corrado Zoccolo wrote:
> Hi Vivek,
> On Wed, Nov 4, 2009 at 12:43 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> > o Previously CFQ had one service tree where queues of all theree prio classes
> >  were being queued. One side affect of this time stamping approach is that
> >  now single tree approach might not work and we need to keep separate service
> >  trees for three prio classes.
> >
> Single service tree is no longer true in cfq for-2.6.33.
> Now we have a matrix of service trees, with first dimension being the
> priority class, and second dimension being the workload type
> (synchronous idle, synchronous no-idle, async).
> You can have a look at the series: http://lkml.org/lkml/2009/10/26/482 .
> It may have other interesting influences on your work, as the idle
> introduced at the end of the synchronous no-idle tree, that provides
> fairness also for seeky or high-think-time queues.
> 

Hi Corrado,

Had one more question. Now with dynamic slice length (reduce slice length
to meet target latency), don't wee see reduced throughput on rotational
media with sequential workload?

I saw some you posted numbers for SSD. Do you have some numbers for
rotational media also?

Thanks
Vivek
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