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

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Date:	Wed, 14 Feb 2007 15:47:31 -0500
From:	Dave Jones <davej@...hat.com>
To:	Marcelo Tosatti <marcelo@...ck.org>
Cc:	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 06:17:36PM -0200, Marcelo Tosatti wrote:
 > On Wed, Feb 14, 2007 at 02:55:46PM -0500, Dave Jones wrote:
 > > On Wed, Feb 14, 2007 at 05:08:39PM -0200, Marcelo Tosatti wrote:
 > >  > 
 > >  > movntq instruction is supported by Geode CPU's, so use
 > >  > fast_clear_page/fast_copy_page versions that have it.
 > > 
 > > it's supported, but is it a win ?
 > > The same was also true of the VIA C3/C7's, but due to
 > > poor memory bandwidth, it turned out to be slower in most cases.
 > 
 > Do you have the numbers for VIA C3/C7 around?

I don't, and my 3dnow capable C3s are unplugged right now.
The newer generation (including the C7) have SSE/SSE2 instead,
which seems to be faster.  (Using a different benchmark app that uses SSE)

clear_page function 'normal clear_page()'        took 9425 cycles per page (620.3 MB/s)
clear_page function 'new clear_page()   '        took 3840 cycles per page (1522.7 MB/s)

copy_page function 'normal copy_page()'  took 11453 cycles per page (510.5 MB/s)
copy_page function 'new copy_page()   '  took 5024 cycles per page (1163.7 MB/s)


		Dave

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