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Date: Thu, 11 Apr 2013 22:46:49 -0400
From: Rik van Riel <riel@redhat.com>
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To: Mel Gorman <mgorman@suse.de>
CC: Andrew Morton <akpm@linux-foundation.org>, Jiri Slaby <jslaby@suse.cz>,
        Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
        Zlatko Calusic <zcalusic@bitsync.net>,
        Johannes Weiner <hannes@cmpxchg.org>, dormando <dormando@rydia.net>,
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        Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdat
 based on reclaim progress
References: <1365505625-9460-1-git-send-email-mgorman@suse.de> <1365505625-9460-5-git-send-email-mgorman@suse.de>
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On 04/09/2013 07:06 AM, Mel Gorman wrote:
> In the past, kswapd makes a decision on whether to compact memory after the
> pgdat was considered balanced. This more or less worked but it is late to
> make such a decision and does not fit well now that kswapd makes a decision
> whether to exit the zone scanning loop depending on reclaim progress.
>
> This patch will compact a pgdat if at least the requested number of pages
> were reclaimed from unbalanced zones for a given priority. If any zone is
> currently balanced, kswapd will not call compaction as it is expected the
> necessary pages are already available.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>

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

This has the potential to increase kswapd cpu use, but probably at
the benefit of making reclaim run a little more smoothly. It should
help that compaction is only called when enough pages have been
freed.

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