linux-kernel - Re: [PATCH 3/3] mm: slub: Default slub_max

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Message-ID: <20110512180921.GP11579@random.random>
Date:	Thu, 12 May 2011 20:09:21 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Dave Jones <davej@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Colin King <colin.king@...onical.com>,
	Raghavendra D Prabhu <raghu.prabhu13@...il.com>,
	Jan Kara <jack@...e.cz>, Chris Mason <chris.mason@...cle.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0

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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