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Subject: Re: [PATCH 13/40] autonuma: CPU follow memory algorithm
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri, 29 Jun 2012 20:51:45 +0200
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To: Rik van Riel <riel@redhat.com>
Cc: dlaor@redhat.com, Ingo Molnar <mingo@kernel.org>, Hillf Danton <dhillf@gmail.com>, Andrea Arcangeli <aarcange@redhat.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dan Smith <danms@us.ibm.com>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>, Suresh Siddha <suresh.b.siddha@intel.com>, Mike Galbraith <efault@gmx.de>, "Paul E.
 McKenney" <paulmck@linux.vnet.ibm.com>, Lai Jiangshan <laijs@cn.fujitsu.com>, Bharata B Rao <bharata.rao@gmail.com>, Lee Schermerhorn <Lee.Schermerhorn@hp.com>, Johannes Weiner <hannes@cmpxchg.org>, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>, Christoph Lameter <cl@linux.com>, Alex Shi <alex.shi@intel.com>, Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Don Morris <don.morris@hp.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>

On Fri, 2012-06-29 at 14:46 -0400, Rik van Riel wrote:
> > I've also stated several times that forceful migration in the context o=
f
> > numa balancing must go.
>=20
> I am not convinced about this part either way.
>=20
> I do not see how a migration numa thread (which could potentially
> use idle cpu time) will be any worse than migrate on fault, which
> will always take away time from the userspace process.=20

Any NUMA stuff is long term, it really shouldn't matter on the timescale
of a few jiffies.

NUMA placement should also not over-ride fairness, esp. not by default.

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