linux-kernel - Re: [PATCH 17/31] mm: numa: Avoid double faulting after migrating misplaced page

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Message-ID: <50A3DC54.8010206@redhat.com>
Date:	Wed, 14 Nov 2012 13:00:52 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 17/31] mm: numa: Avoid double faulting after migrating
 misplaced page

On 11/13/2012 06:12 AM, Mel Gorman wrote:
> The pte_same check after a misplaced page is successfully migrated will
> never succeed and force a double fault to fix it up as pointed out by Rik
> van Riel. This was the "safe" option but it's expensive.
>
> This patch uses the migration allocation callback to record the location
> of the newly migrated page. If the page is the same when the PTE lock is
> reacquired it is assumed that it is safe to complete the pte_numa fault
> without incurring a double fault.
>
> Signed-off-by: Mel Gorman <mgorman@...e.de>

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

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