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

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Message-ID: <0000013af701ca15-3acab23b-a16d-4e38-9dc0-efef05cbc5f2-000000@email.amazonses.com>
Date:	Mon, 12 Nov 2012 23:43:41 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc:	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>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/8] Announcement: Enhanced NUMA scheduling with adaptive
 affinity

On Mon, 12 Nov 2012, Peter Zijlstra wrote:

> The biggest conceptual addition, beyond the elimination of the home
> node, is that the scheduler is now able to recognize 'private' versus
> 'shared' pages, by carefully analyzing the pattern of how CPUs touch the
> working set pages. The scheduler automatically recognizes tasks that
> share memory with each other (and make dominant use of that memory) -
> versus tasks that allocate and use their working set privately.

That is a key distinction to make and if this really works then that is
major progress.

> This new scheduler code is then able to group tasks that are "memory
> related" via their memory access patterns together: in the NUMA context
> moving them on the same node if possible, and spreading them amongst
> nodes if they use private memory.

What happens if processes memory accesses  are related but the
common set of data does not fit into the memory provided by a single node?

The correct resolution usually is in that case to interleasve the pages
over both nodes in use.

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