linux-kernel - Re: [ckrm-tech] [RFC] Resource Management

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Date:	Mon, 30 Oct 2006 04:07:20 -0800
From:	"Paul Menage" <menage@...gle.com>
To:	"Paul Jackson" <pj@....com>
Cc:	vatsa@...ibm.com, dev@...nvz.org, sekharan@...ibm.com,
	ckrm-tech@...ts.sourceforge.net, balbir@...ibm.com,
	haveblue@...ibm.com, linux-kernel@...r.kernel.org,
	matthltc@...ibm.com, dipankar@...ibm.com, rohitseth@...gle.com
Subject: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices

On 10/30/06, Paul Jackson <pj@....com> wrote:
> I get away with this in the cpuset code because:
>  1) I have the cpuset pointer directly in 'task_struct', so don't
>     have to chase down anything, for each task, while scanning the
>     task list.  I just have to ask, for each task, if its cpuset
>     pointer points to the cpuset of interest.

That's the same when it's transferred to containers - each task_struct
now has a container pointer, and you can just see whether the
container pointer matches the container that you're interested in.

>  2) I don't care if I get an inconsistent answer, so I don't have
>     to lock each task, nor do I even lockout the rest of the cpuset
>     code.  All I know, at the end of the scan, is that each task that
>     I claim is attached to the cpuset in question was attached to it at
>     some point during my scan, not necessarilly all at the same time.

Well, anything that can be accomplished from within the tasklist_lock
can get a consistent result without any additional lists or
synchronization - it seems that it would be good to come up with a
real-world example of something that *can't* make do with this before
adding extra book-keeping.

Paul
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