Subject: Re: [BUG] rebuild_sched_domains considered dangerous
From: Peter Zijlstra <peterz@infradead.org>
To: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, nfont@austin.ibm.com
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Date: Fri, 03 Jun 2011 16:47:49 +0200
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On Wed, 2011-05-11 at 11:17 -0500, Jesse Larrew wrote:
> > I would really like to see both patch-sets together. Also, I'm not
> at
> > all convinced its a sane thing to do. Pretty much all NUMA aware
> > software I know of assumes that CPU<->NODE relations are static,
> > breaking that in kernel renders all existing software broken.
> > 
> 
> I suspect that's true. Then again, shouldn't it be the capabilities of
> the hardware that dictates what the software does, rather than the
> other way around? 

Wish that were true, we wouldn't be all constrained by all this legacy
software.. ;-)

Anyway, there's plenty of CPU<->NODE assumptions in the kernel as well,
fixing those will be 'interesting' at best, as for userspace, since its
a user-driven tool revamping the topology the user gets to keep the
pieces when he runs that while some NUMA aware proglet is running.
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