linux-kernel - Re: [PATCH] io-controller: optimization for iog deletion when elevator exiting

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Message-ID: <20090701013425.GC13958@redhat.com>
Date:	Tue, 30 Jun 2009 21:34:25 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Nauman Rafique <nauman@...gle.com>
Cc:	Gui Jianfeng <guijianfeng@...fujitsu.com>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	ryov@...inux.co.jp, fernando@....ntt.co.jp, s-uchida@...jp.nec.com,
	taka@...inux.co.jp, jmoyer@...hat.com, dhaval@...ux.vnet.ibm.com,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, jbaron@...hat.com, agk@...hat.com,
	snitzer@...hat.com, akpm@...ux-foundation.org, peterz@...radead.org
Subject: Re: [PATCH] io-controller: optimization for iog deletion when
	elevator exiting

On Tue, Jun 30, 2009 at 10:14:48AM -0700, Nauman Rafique wrote:
> On Mon, Jun 29, 2009 at 7:06 AM, Vivek Goyal<vgoyal@...hat.com> wrote:
> > On Mon, Jun 29, 2009 at 01:27:47PM +0800, Gui Jianfeng wrote:
> >> Hi Vivek,
> >>
> >> There's no need to travel the iocg->group_data for each iog
> >> when exiting a elevator, that costs too much. An alternative
> >> solution is reseting iocg_id as soon as an io group unlinking
> >> from a iocg. Make a decision that whether it's need to carry
> >> out deleting action by checking iocg_id.
> >>
> >
> > Thanks Gui. This makes sense to me. We can check iog->iocg_id to determine
> > wheter group is still on iocg list or not instead of traversing the list.
> >
> > Nauman, do you see any issues with the patch?
> 
> Looks like this should work. The only iog with zero id is associated
> with root group, which gets deleted outside of this function anyways.
> 

Minor correction. Even root group has id "1" and not zero. 0 is associated
with error when cgroup is not present.

Thanks
Vivek
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