linux-kernel - Re: [RFC] cpuset: remove sched domain hooks from cpusets

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Message-ID: <20061020102946.A8481@unix-os.sc.intel.com>
Date:	Fri, 20 Oct 2006 10:29:46 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Martin Bligh <mbligh@...gle.com>, Paul Jackson <pj@....com>,
	akpm@...l.org, menage@...gle.com, Simon.Derr@...l.net,
	linux-kernel@...r.kernel.org, dino@...ibm.com,
	rohitseth@...gle.com, holt@....com, dipankar@...ibm.com,
	suresh.b.siddha@...el.com
Subject: Re: [RFC] cpuset: remove sched domain hooks from cpusets

On Sat, Oct 21, 2006 at 02:03:22AM +1000, Nick Piggin wrote:
> Martin Bligh wrote:
> > We (Google) are planning to use it to do some partitioning, albeit on
> > much smaller machines. I'd really like to NOT use cpus_allowed from
> > previous experience - if we can get it to to partition using separated
> > sched domains, that would be much better.
> > 
> >  From my dim recollections of previous discussions when cpusets was
> > added in the first place, we asked for exactly the same thing then.
> > I think some of the problem came from the fact that "exclusive"
> > to cpusets doesn't actually mean exclusive at all, and they're
> > shared in some fashion. Perhaps that issue is cleared up now?
> > /me crosses all fingers and toes and prays really hard.
> 
> The I believe, is that an exclusive cpuset can have an exclusive parent
> and exclusive children, which obviously all overlap one another, and
> thus you have to do the partition only at the top-most exclusive cpuset.
> 
> Currently, cpusets is creating partitions in cpus_exclusive children as
> well, which breaks balancing for the parent.
> 
> The patch I posted previously should (modulo bugs) only do partitioning
> in the top-most cpuset. I still need clarification from Paul as to why
> this is unacceptable, though.

I like the direction of Nick's patch which do domain partitioning at the
top-most exclusive cpuset.

thanks,
suresh
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