linux-kernel - Re: [PATCH 0/8] Announcement: Enhanced NUMA scheduling with adaptive affinity

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Message-ID: <0000013b0b031a8f-e57805ad-a81f-4aa7-9906-ceb99f41210b-000000@email.amazonses.com>
Date:	Fri, 16 Nov 2012 20:57:31 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Ingo Molnar <mingo@...nel.org>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Paul Turner <pjt@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/8] Announcement: Enhanced NUMA scheduling with adaptive
 affinity

On Fri, 16 Nov 2012, Ingo Molnar wrote:

> > The interleaving of memory areas that have an equal amount of
> > shared accesses from multiple nodes is essential to limit the
> > traffic on the interconnect and get top performance.
>
> That is true only if the load is symmetric.

Which is usually true of an HPC workload.

> > I guess through that in a non HPC environment where you are
> > not interested in one specific load running at top speed
> > varying contention on the interconnect and memory busses are
> > acceptable. But this means that HPC loads cannot be auto
> > tuned.
>
> I'm not against improving these workloads (at all) - I just
> pointed out that interleaving isn't necessarily the best
> placement strategy for 'large' workloads.

Depends on what you mean by "large" workloads. If it is a typically large
HPC workload with data structures distributed over nodes then the
placement of those data structure spread over all nodes is the best
placement startegy.
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