linux-kernel - Re: [PATCH 27/63] mm: numa: Scan pages with elevated page

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Date:	Mon, 07 Oct 2013 14:43:58 -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 27/63] mm: numa: Scan pages with elevated page_mapcount

On 10/07/2013 06:29 AM, Mel Gorman wrote:
> Currently automatic NUMA balancing is unable to distinguish between false
> shared versus private pages except by ignoring pages with an elevated
> page_mapcount entirely. This avoids shared pages bouncing between the
> nodes whose task is using them but that is ignored quite a lot of data.
> 
> This patch kicks away the training wheels in preparation for adding support
> for identifying shared/private pages is now in place. The ordering is so
> that the impact of the shared/private detection can be easily measured. Note
> that the patch does not migrate shared, file-backed within vmas marked
> VM_EXEC as these are generally shared library pages. Migrating such pages
> is not beneficial as there is an expectation they are read-shared between
> caches and iTLB and iCache pressure is generally low.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

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

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