linux-kernel - Re: [PATCH][RFCv2] mm/compaction: reset compaction scanner positions

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Date:	Fri, 20 Mar 2015 14:49:34 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Gioh Kim <gioh.kim@....com>, akpm@...ux-foundation.org,
	rientjes@...gle.com, iamjoonsoo.kim@....com, mgorman@...e.de
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, gunho.lee@....com
Subject: Re: [PATCH][RFCv2] mm/compaction: reset compaction scanner positions

On 03/20/2015 02:00 PM, Gioh Kim wrote:
> I'm attaching the patch for discussion.
> According to Vlastimil's advice, I move the reseting before compact_zone(),
> and write more description.
>
> Vlastimil, can I have your name at Acked-by or Signed-off-by?

Yes. But note below that whitespace seems broken in the patch.

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> Which one do you prefer?

Acked-by, as Signed-off-by is for maintainers who resend the patches 
towards Linus.

> ------------------------- 8< ----------------------
>
>   From 575983c887e6478ca7cbba49a892dbc4cd69986b Mon Sep 17 00:00:00 2001
> From: Gioh Kim <gioh.kim@....com>
> Date: Fri, 20 Mar 2015 21:09:13 +0900
> Subject: [PATCH] [RFCv2] mm/compaction: reset compaction scanner positions
>
> When the compaction is activated via /proc/sys/vm/compact_memory
> it would better scan the whole zone.
> And some platform, for instance ARM, has the start_pfn of a zone as zero.
> Therefore the first try to compaction via /proc doesn't work.
> It needs to force to reset compaction scanner position at first.
>
> Signed-off-by: Gioh Kim <gioh.kim@....com>
> ---
>    mm/compaction.c |    8 ++++++++
>    1 file changed, 8 insertions(+)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 8c0d945..ccf48ce 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1587,6 +1587,14 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
>                   INIT_LIST_HEAD(&cc->freepages);
>                   INIT_LIST_HEAD(&cc->migratepages);
>
> +               /*
> +                * When called via /proc/sys/vm/compact_memory
> +                * this makes sure we compact the whole zone regardless of
> +                * cached scanner positions.
> +                */
> +               if (cc->order == -1)
> +                       __reset_isolation_suitable(zone);

Indentation seems off, some tabs vs spaces issue?

> +
>                   if (cc->order == -1 || !compaction_deferred(zone, cc->order))
>                           compact_zone(zone, cc);
>
> --
> 1.7.9.5
>
>
> --
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