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

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Message-Id: <20091008.192242.39182274.ryov@valinux.co.jp>
Date:	Thu, 08 Oct 2009 19:22:42 +0900 (JST)
From:	Ryo Tsuruta <ryov@...inux.co.jp>
To:	riel@...hat.com
Cc:	vgoyal@...hat.com, nauman@...gle.com, m-ikeda@...jp.nec.com,
	linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
	containers@...ts.linux-foundation.org, dm-devel@...hat.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, agk@...hat.com, akpm@...ux-foundation.org,
	peterz@...radead.org, jmarchan@...hat.com,
	torvalds@...ux-foundation.org, mingo@...e.hu,
	yoshikawa.takuya@....ntt.co.jp
Subject: Re: IO scheduler based IO controller V10

Hi Rik,

Rik van Riel <riel@...hat.com> wrote:
> Ryo Tsuruta wrote:
> 
> > If once dm-ioband is integrated into the LVM tools and bandwidth can
> > be assigned per device by lvcreate, the use of dm-tools is no longer
> > required for users.
> 
> A lot of large data center users have a SAN, with volume management
> handled SAN-side and dedicated LUNs for different applications or
> groups of applications.
> 
> Because of alignment issues, they typically use filesystems directly
> on top of the LUNs, without partitions or LVM layers.  We cannot rely
> on LVM for these systems, because people prefer not to use that.

Thank you for your explanation. So I have a plan to reimplement
dm-ioband into the block layer to make dm-tools no longer required.
My opinion I wrote above assumes if dm-ioband is used for a logical
volume which consists of multiple physical devices. If dm-ioband is
integrated into the LVM tools, then the use of the dm-tools is not
required and the underlying physical devices can be automatically
deteced and configured to use dm-ioband.

Thanks,
Ryo Tsuruta

> Besides ... isn't the goal of the cgroups io bandwidth controller
> to control the IO used by PROCESSES?
>
> If we want to control processes, why would we want the configuration
> to be applied to any other kind of object in the system?
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