From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <raistlin@linux.it>
Subject: Re: [PATCH 1 of 3 v5/leftover] libxl: enable automatic
 placement of guests on NUMA nodes [and 1 more messages]
Date: Sat, 21 Jul 2012 03:46:32 +0200
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To: Andre Przywara <andre.przywara@amd.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>, Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>, George Dunlap <George.Dunlap@eu.citrix.com>, Juergen Gross <juergen.gross@ts.fujitsu.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, xen-devel <xen-devel@lists.xen.org>
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On Thu, 2012-07-19 at 20:37 +0200, Andre Przywara wrote:
> > But it's OK, we don't need to panic.  We just need a safety catch
> > which stops this algorithm running in situations where it won't work.
> > Following a discussion with Dario, AIUI he plans to implement a rule
> > that it will bail on systems with more than 8 NUMA nodes.
> >
> > That is releasable in 4.2 and ought to be satisfactory for you ?
>=20
I did right that. Honestly, I computed the exact amount of steps the
algorithm needs in the worst case (i.e., searching all the combinations
of all the sizes) for 8 and 16 nodes. 8 nodes means 256 steps, 16 nodes
means 65536, so I think both could work, especially after the
optimization I put in the version I just released (it does not uses that
large array of combinations and does not need to always perform all the
steps any longer).

However, as agreed, I put an "if (nr_nodes <=3D 8)" there... If a 16 nodes
machine will ever appear, we'll decide what to do.

> Absolutely, that's fine. I just wanted to make sure that we don't drop=
=20
> the patches at all because of the theoretical fear of a large NUMA box=
=20
> lingering somewhere around the corner...
>=20
:-)

Thanks and Regards,
Dario

--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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