linux-kernel - Re: [PATCH 07/63] mm: numa: Sanitize task_numa

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Date:	Mon, 07 Oct 2013 10:02:12 -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 07/63] mm: numa: Sanitize task_numa_fault() callsites

On 10/07/2013 06:28 AM, Mel Gorman wrote:
> There are three callers of task_numa_fault():
> 
>  - do_huge_pmd_numa_page():
>      Accounts against the current node, not the node where the
>      page resides, unless we migrated, in which case it accounts
>      against the node we migrated to.
> 
>  - do_numa_page():
>      Accounts against the current node, not the node where the
>      page resides, unless we migrated, in which case it accounts
>      against the node we migrated to.
> 
>  - do_pmd_numa_page():
>      Accounts not at all when the page isn't migrated, otherwise
>      accounts against the node we migrated towards.
> 
> This seems wrong to me; all three sites should have the same
> sementaics, furthermore we should accounts against where the page
> really is, we already know where the task is.
> 
> So modify all three sites to always account; we did after all receive
> the fault; and always account to where the page is after migration,
> regardless of success.
> 
> They all still differ on when they clear the PTE/PMD; ideally that
> would get sorted too.
> 
> Cc: stable <stable@...r.kernel.org>
> 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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