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Date: Wed, 18 Dec 2013 16:48:15 -0800
From: Dave Hansen <dave@sr71.net>
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Christoph Lameter <cl@linux.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Pravin B Shelar <pshelar@nicira.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Pekka Enberg <penberg@kernel.org>
Subject: Re: [RFC][PATCH 0/7] re-shrink 'struct page' when SLUB is on.
References: <20131213235903.8236C539@viggo.jf.intel.com>	<20131216160128.aa1f1eb8039f5eee578cf560@linux-foundation.org>	<52AF9EB9.7080606@sr71.net>	<0000014301223b3e-a73f3d59-8234-48f1-9888-9af32709a879-000000@email.amazonses.com>	<52B23CAF.809@sr71.net> <20131218164109.5e169e258378fac44ec5212d@linux-foundation.org>
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On 12/18/2013 04:41 PM, Andrew Morton wrote:
>> > Unless somebody can find some holes in this, I think we have no choice
>> > but to unset the HAVE_ALIGNED_STRUCT_PAGE config option and revert using
>> > the cmpxchg, at least for now.
>
> So your scary patch series which shrinks struct page while retaining
> the cmpxchg_double() might reclaim most of this loss?

That's what I'll test next, but I hope so.

The config tweak is important because it shows a low-risk way to get a
small 'struct page', plus get back some performance that we lost and
evidently never noticed.  A distro that was nearing a release might want
to go with this, for instance.