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Re: Changing the default 32-bit x86 arch for Fedora 12



On Mon, Jun 15, 2009 at 06:04:15PM -0400, Bill Nottingham wrote:
>Gregory Maxwell (gmaxwell gmail com) said: 
>> Is dropping hardware worth this instruction? I suggested some
>> benchmarking and demonstrated that it's a very small improvement for
>> Theora. I'm not sure if anyone got around to testing freetype,
>> firefox, or any of the other couple CPU heavy desktop apps.
>> 
>> It would probably be most interesting to perform that test on the
>> x86-only ATOM, since I can see CMOV being a bigger win on an in-order
>> CPU.
>> 
>> (I can't personally protest: I think all the x86 stuff I have has CMOV).
>
>Last time I profiled it (using the bits of openbench that actually worked),
>i586 -> i686 was an improvement of 1% (Core2Duo) to 2% (Atom). Athlon64 was
>essentially equal.
>
>SPECCPU results showed similar. 

Wasn't code paths in glibc and possibly other packages a concern?  I seem to
remember the glibc maintainer not being happy with using i586 at all, but
conceded to it as a path to i686.

josh


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