Changing the default 32-bit x86 arch for Fedora 12 (#2)
Bob Arendt
rda at rincon.com
Thu Jun 18 04:45:31 UTC 2009
On 06/17/2009 03:00 PM, Richard W.M. Jones wrote:
> On Wed, Jun 17, 2009 at 01:52:26PM -0400, Bill Nottingham wrote:
>> - Build all packages for i686 (this requires cmov)
>
> This cuts out AMD Geode ...
>
> and for what ...
>
>> P4 2.4Ghz Athlon 3400+ Core2Duo E6850 Atom N270
>> march=i686/ -1.1% +2.0% +0.9% +0.6%
>> mtune=generic
>> march=i586/ +0.3% -0.3% -0.2% +1.3%
>> mtune=atom
>> march=i686/ -1.5% +1.2% +0.5% +1.7%
>> mtune=atom
>
> This just doesn't look worthwhile at all.
>
> My proposal is that we actually start to 'downgrade' x86, start
> compiling for baseline i386, and try to support people running Fedora
> on really old hardware, through projects like the Minimal Platform
> feature.
>
> Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
Agreeing with Rich, what does this buy us? Being generous, 1.7% means
you shaved 1 second off a 1 minute mp3 encode. Perhaps measurement
accuracy is on the order of 0.5%? And the P4 performance degrades; Why
further cripple the slower chip?
This slight benefit doesn't seem worth the effort of re-doing the build
infrastructure and dropping/alienating older chip architectures.
-Bob Arendt
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