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Date: Thu, 06 Dec 2012 15:32:18 -0500
From: Rik van Riel <riel@redhat.com>
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To: Johannes Weiner <hannes@cmpxchg.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Bruno Wolff III <bruno@wolff.to>,
        Thorsten Leemhuis <fedora@leemhuis.info>, Mel Gorman <mgorman@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        George Spelvin <linux@horizon.com>,
        Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>,
        Tomas Racek <tracek@redhat.com>, Jan Kara <jack@suse.cz>,
        Dave Hansen <dave@linux.vnet.ibm.com>, Josh Boyer <jwboyer@gmail.com>,
        Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
        Jiri Slaby <jslaby@suse.cz>, Zdenek Kabelac <zkabelac@redhat.com>,
        linux-mm <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        John Ellson <john.ellson@comcast.net>
Subject: Re: kswapd craziness in 3.7
References: <50B77F84.1030907@leemhuis.info> <20121129170512.GI2301@cmpxchg.org> <50B8A8E7.4030108@leemhuis.info> <20121201004520.GK2301@cmpxchg.org> <50BC6314.7060106@leemhuis.info> <20121203194208.GZ24381@cmpxchg.org> <20121204214210.GB20253@cmpxchg.org> <20121205030133.GA17438@wolff.to> <20121206173742.GA27297@wolff.to> <CA+55aFzZsCUk6snrsopWQJQTXLO__G7=SjrGNyK3ePCEtZo7Sw@mail.gmail.com> <20121206202325.GA1498@cmpxchg.org>
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On 12/06/2012 03:23 PM, Johannes Weiner wrote:

> From: Johannes Weiner <hannes@cmpxchg.org>
> Subject: [patch] mm: vmscan: fix inappropriate zone congestion clearing
>
> c702418 ("mm: vmscan: do not keep kswapd looping forever due to
> individual uncompactable zones") removed zone watermark checks from
> the compaction code in kswapd but left in the zone congestion
> clearing, which now happens unconditionally on higher order reclaim.
>
> This messes up the reclaim throttling logic for zones with
> dirty/writeback pages, where zones should only lose their congestion
> status when their watermarks have been restored.
>
> Remove the clearing from the zone compaction section entirely.  The
> preliminary zone check and the reclaim loop in kswapd will clear it if
> the zone is considered balanced.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

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


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