From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0
Date: Thu, 12 May 2011 20:09:21 +0200
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Cc: Pekka Enberg <penberg@kernel.org>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Dave Jones <davej@redhat.com>, Mel Gorman <mgorman@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Colin King <colin.king@canonical.com>,
        Raghavendra D Prabhu <raghu.prabhu13@gmail.com>,
        Jan Kara <jack@suse.cz>, Chris Mason <chris.mason@oracle.com>,
        Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-ext4 <linux-ext4@vger.kernel.org>
To: Christoph Lameter <cl@linux.com>
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On Thu, May 12, 2011 at 01:03:05PM -0500, Christoph Lameter wrote:
> On Thu, 12 May 2011, Andrea Arcangeli wrote:
> 
> > even order 3 is causing troubles (which doesn't immediately make lumpy
> > activated, it only activates when priority is < DEF_PRIORITY-2, so
> > after 2 loops failing to reclaim nr_to_reclaim pages), imagine what
> 
> That is a significant change for SLUB with the merge of the compaction
> code.

Even before compaction was posted, I had to shut off lumpy reclaim or
it'd hang all the time with frequent order 9 allocations. Maybe lumpy
was better before, maybe lumpy "improved" its reliability recently,
but definitely it wasn't performing well. That definitely applies to
>=2.6.32 (I had to nuke lumpy from it, and only keep compaction
enabled, pretty much like upstream with COMPACTION=y). I think I never
tried earlier lumpy code than 2.6.32, maybe it was less aggressive
back then, I don't exclude it but I thought the whole notion of lumpy
was to takedown everything in the way, which usually leads to process
hanging in swapins or pageins for frequent used memory.

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