linux-kernel - Re: i686 quirk for AMD Geode

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Date:	Sun, 8 Nov 2009 18:37:08 +0100
From:	Pavel Machek <pavel@....cz>
To:	Matteo Croce <technoboy85@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

On Fri 2009-11-06 23:18:06, Matteo Croce wrote:
> On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa@...or.com> wrote:
> > On 11/06/2009 06:59 AM, Matteo Croce wrote:
> >> indeed it has MMX, MMXEXT and CMOV, just lacks the long NOP instruction (NOPL).
> >
> > MMX and MMXEXT are hardly hallmarks of i686, which leaves only cmov.
> > I'm somewhat wondering about the general value of this patch; is i686
> > code really that much faster on Geode that it's worth it?
> >
> > ? ? ? ?-hpa
> >
> > --
> > H. Peter Anvin, Intel Open Source Technology Center
> > I work for Intel. ?I don't speak on their behalf.
> >
> >
> 
> yes, I did some test like gzip, bzip2, lame etc and they give more or less
> the same results of dhrystone
> 
> root@...x:/usr/src# CFLAGS='-march=i586' ./dry.c
> Microseconds for one run through Dhrystone:        1.4
> Dhrystones per Second:                          740741
...
> root@...x:/usr/src# CFLAGS='-march=i686' ./dry.c
> Trying 5000000 runs through Dhrystone:
> Microseconds for one run through Dhrystone:        1.2
> Dhrystones per Second:                          841751

Teach gcc that geodelx exists? No need to break kernel for that... and
you probably can gain even bigger gains.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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