linux-kernel - Re: [RFC][PATCH 0/7] re-shrink 'struct page' when SLUB is on.

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Message-ID: <alpine.DEB.2.10.1312190920340.4238@nuc>
Date:	Thu, 19 Dec 2013 09:21:15 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Dave Hansen <dave@...1.net>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Pravin B Shelar <pshelar@...ira.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [RFC][PATCH 0/7] re-shrink 'struct page' when SLUB is on.

On Wed, 18 Dec 2013, Dave Hansen wrote:

> 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.

Ok then lets just drop the cmpxchg updates to the page struct. The
spinlock code is already in there so just removing the __CMPXCHG flag
related processing should do the trick.

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