From: James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0
Date: Thu, 12 May 2011 14:44:07 -0500
Message-ID: <1305229447.2575.71.camel@mulgrave.site>
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Cc: Christoph Lameter <cl@linux.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: Pekka Enberg <penberg@kernel.org>
In-Reply-To: <1305225467.2575.66.camel@mulgrave.site>
Sender: linux-ext4-owner@vger.kernel.org

On Thu, 2011-05-12 at 13:37 -0500, James Bottomley wrote:
> On Thu, 2011-05-12 at 18:55 +0300, Pekka Enberg wrote:
> > On Thu, 2011-05-12 at 10:43 -0500, James Bottomley wrote:
> > > However, since you admit even you see problems, let's concentrate on
> > > fixing them rather than recriminations?
> > 
> > Yes, please. So does dropping max_order to 1 help?
> > PAGE_ALLOC_COSTLY_ORDER is set to 3 in 2.6.39-rc7.
> 
> Just booting with max_slab_order=1 (and none of the other patches
> applied) I can still get the machine to go into kswapd at 99%, so it
> doesn't seem to make much of a difference.
> 
> Do you want me to try with the other two patches and max_slab_order=1?

OK, so patches 1 + 2 plus setting slub_max_order=1 still manages to
trigger the problem (kswapd spinning at 99%).  This is still with
PREEMPT; it's possible that non-PREEMPT might be better, so I'll try
patches 1+2+3 with PREEMPT just to see if the perturbation is caused by
it.

James