linux-kernel - Re: [PATCH 43/63] sched: numa: Use {cpu, pid} to create task groups for shared faults

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Message-ID: <525306DE.4090102@redhat.com>
Date:	Mon, 07 Oct 2013 15:09:18 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 43/63] sched: numa: Use {cpu, pid} to create task groups
 for shared faults

On 10/07/2013 06:29 AM, Mel Gorman wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> 
> While parallel applications tend to align their data on the cache
> boundary, they tend not to align on the page or THP boundary.
> Consequently tasks that partition their data can still "false-share"
> pages presenting a problem for optimal NUMA placement.
> 
> This patch uses NUMA hinting faults to chain tasks together into
> numa_groups. As well as storing the NID a task was running on when
> accessing a page a truncated representation of the faulting PID is
> stored. If subsequent faults are from different PIDs it is reasonable
> to assume that those two tasks share a page and are candidates for
> being grouped together. Note that this patch makes no scheduling
> decisions based on the grouping information.
> 
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Rik van Riel <riel@...hat.com>


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