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Message-ID: <6599ad830610300407x674059ebh8337d05a4e8ebe85@mail.gmail.com>
Date: Mon, 30 Oct 2006 04:07:20 -0800
From: "Paul Menage" <menage@google.com>
To: "Paul Jackson" <pj@sgi.com>
Subject: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices
Cc: vatsa@in.ibm.com, dev@openvz.org, sekharan@us.ibm.com,
       ckrm-tech@lists.sourceforge.net, balbir@in.ibm.com, haveblue@us.ibm.com,
       linux-kernel@vger.kernel.org, matthltc@us.ibm.com, dipankar@in.ibm.com,
       rohitseth@google.com
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On 10/30/06, Paul Jackson <pj@sgi.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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