linux-kernel - Re: [PATCH 35/63] sched: numa: Do not trap hinting faults for shared libraries

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Message-ID: <525305D6.2020205@redhat.com>
Date:	Mon, 07 Oct 2013 15:04:54 -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 35/63] sched: numa: Do not trap hinting faults for shared
 libraries

On 10/07/2013 06:29 AM, Mel Gorman wrote:
> NUMA hinting faults will not migrate a shared executable page mapped by
> multiple processes on the grounds that the data is probably in the CPU
> cache already and the page may just bounce between tasks running on multipl
> nodes. Even if the migration is avoided, there is still the overhead of
> trapping the fault, updating the statistics, making scheduler placement
> decisions based on the information etc. If we are never going to migrate
> the page, it is overhead for no gain and worse a process may be placed on
> a sub-optimal node for shared executable pages. This patch avoids trapping
> faults for shared libraries entirely.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

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