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Date: Wed, 6 Jun 2012 09:11:17 +0200
From: Ingo Molnar <mingo@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: a.p.zijlstra@chello.nl, hpa@zytor.com, linux-kernel@vger.kernel.org,
        yinghai@kernel.org, tj@kernel.org, tglx@linutronix.de,
        linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] x86/numa: Allow specifying node_distance() for
 numa=fake
Message-ID: <20120606071117.GE17808@gmail.com>
References: <tip-e1136ef7kdffj7yf9tjhydln@git.kernel.org>
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* David Rientjes <rientjes@google.com> wrote:

> On Wed, 9 May 2012, tip-bot for Peter Zijlstra wrote:
> 
> > Commit-ID:  94c0dd3278dd3eae52eabf0fb77d472d0dd3e373
> > Gitweb:     http://git.kernel.org/tip/94c0dd3278dd3eae52eabf0fb77d472d0dd3e373
> > Author:     Peter Zijlstra <a.p.zijlstra@chello.nl>
> > AuthorDate: Wed, 18 Apr 2012 19:04:17 +0200
> > Committer:  Ingo Molnar <mingo@kernel.org>
> > CommitDate: Wed, 9 May 2012 13:28:59 +0200
> > 
> > x86/numa: Allow specifying node_distance() for numa=fake
> > 
> > Allows emulating more interesting NUMA configurations like a quad
> > socket AMD Magny-Cour:
> > 
> >  "numa=fake=8:10,16,16,22,16,22,16,22,
> >               16,10,22,16,22,16,22,16,
> >               16,22,10,16,16,22,16,22,
> >               22,16,16,10,22,16,22,16,
> >               16,22,16,22,10,16,16,22,
> >               22,16,22,16,16,10,22,16,
> >               16,22,16,22,16,22,10,16,
> >               22,16,22,16,22,16,16,10"
> > 
> > Which has a non-fully-connected topology.
> > 
> 
> I like this support and I'm pretty sure you used it to 
> reproduce my problems with sched/numa locally, but I think it 
> would be better to seperate it out as a different parameter 
> such as slit=fake so that we can still use it to fake the SLIT 
> of our NUMA machines without requiring numa=fake which 
> provides no guarantees to break the nodes along physical 
> boundaries.
> 
> So without seperating it out into slit=fake, we can't change 
> this information without changing the SLIT itself and that 
> makes debugging harder.

Makes sense - wanna send a patch?

Thanks,

	Ingo