linux-kernel - Re: [PATCH 3/4] Pte xchg optimization.patch

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Message-ID: <20070412181809.GC25646@redhat.com>
Date:	Thu, 12 Apr 2007 14:18:09 -0400
From:	Dave Jones <davej@...hat.com>
To:	Zachary Amsden <zach@...are.com>
Cc:	Andrew Morton <akpm@...l.org>, Andi Kleen <ak@....de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Chris Wright <chrisw@...s-sol.org>,
	Hugh Dickins <hugh@...itas.com>,
	David Rientjes <rientjes@...gle.com>,
	Michel Lespinasse <walken@...are.com>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] Pte xchg optimization.patch

On Wed, Apr 11, 2007 at 10:30:58PM -0700, Zachary Amsden wrote:
 > In situations where page table updates need only be made locally, and there
 > is no cross-processor A/D bit races involved, we need not use the heavyweight
 > xchg instruction to atomically fetch and clear page table entries.  Instead,
 > we can just read and clear them directly.
 > 
 > This introduces a neat optimization for non-SMP kernels; drop the atomic
 > xchg operations from page table updates.

Would it be feasible to do this using the smp_alternatives stuff?
Given many distros are now shipping SMP-only kernels, it'd be nice
to get that win without using having to rebuild their kernels.

	Dave

-- 
http://www.codemonkey.org.uk
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