linux-kernel - Re: [PATCH] use movntq version of fast_clear_page/fast_copy

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Message-ID: <20070215150116.GA5751@dmt.media.mit.edu>
Date:	Thu, 15 Feb 2007 13:01:16 -0200
From:	Marcelo Tosatti <marcelo@...ck.org>
To:	Alan <alan@...rguk.ukuu.org.uk>
Cc:	Marcelo Tosatti <marcelo@...ck.org>,
	Jordan Crouse <jordan.crouse@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] use movntq version of fast_clear_page/fast_copy_page on Geode

On Wed, Feb 14, 2007 at 09:16:46PM +0000, Alan wrote:
> On Wed, 14 Feb 2007 17:08:39 -0200
> Marcelo Tosatti <marcelo@...ck.org> wrote:
> 
> > 
> > movntq instruction is supported by Geode CPU's, so use
> > fast_clear_page/fast_copy_page versions that have it.
> 
> Is it actually faster for macro performance not just microbenchmarking ?

A COW intensive private mmap() benchmark shows the kernel spending
_more_ time inside mmx_copy_page() with movntq than with movq.

So its not clear whether the patch is actually a win, please drop it.

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