linux-kernel - Re: IO scheduler based IO controller V10

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Message-Id: <20090928.163811.104053649.ryov@valinux.co.jp>
Date:	Mon, 28 Sep 2009 16:38:11 +0900 (JST)
From:	Ryo Tsuruta <ryov@...inux.co.jp>
To:	riel@...hat.com
Cc:	vgoyal@...hat.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp,
	guijianfeng@...fujitsu.com, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	righi.andrea@...il.com, m-ikeda@...jp.nec.com, agk@...hat.com,
	peterz@...radead.org, jmarchan@...hat.com,
	torvalds@...ux-foundation.org, mingo@...e.hu
Subject: Re: IO scheduler based IO controller V10

Hi Rik,

Rik van Riel <riel@...hat.com> wrote:
> Ryo Tsuruta wrote:
> 
> > Because dm-ioband provides faireness in terms of how many IO requests
> > are issued or how many bytes are transferred, so this behaviour is to
> > be expected. Do you think fairness in terms of IO requests and size is
> > not fair?
> 
> When there are two workloads competing for the same
> resources, I would expect each of the workloads to
> run at about 50% of the speed at which it would run
> on an uncontended system.
> 
> Having one of the workloads run at 95% of the
> uncontended speed and the other workload at 5%
> is "not fair" (to put it diplomatically).

As I wrote in the mail to Vivek, I think that providing multiple
policies, on a per disk time basis, on a per iosize basis, maximum
rate limiting or etc would be good for users.

Thanks,
Ryo Tsuruta
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