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Re: compilation architecture



Jakub 'Livio' Rusinek wrote:
I've used openSUSE (i586) with the same configuration and packages installed and eg. Firefox 3 was started in < 1 sec. I have no benchmarks but everything runs faster and is more responsible.

Our optimalization does nothing compared to > i386 compilation.

False. On modern processors, with most userspace code, building for i586 generates code with instruction scheduling that is *slower* than i386 instructions tuned for i686. This is why Fedora builds most packages as i386, tuned for i686.

i586 really only makes sense for things like the kernel, glibc, JVMs, and multimedia/hpc libraries that use MMX/SSE instructions. In these cases, i686 will usually be even better, though it occasionally makes sense to build with i586 instructions and tune for i686 if you want to have one package that'll work acceptably on i586 and work very well on i686.

On a typical desktop system, you'll never notice the difference between i386, i586, and i686 packages except with high-performance graphics. Your experience with openSUSE is interesting, but it is not related to compiler optimizations.

	-- Chris

2008/1/12, drago01 <drago01 gmail com <mailto:drago01 gmail com>>:

    2008/1/12 Jakub 'Livio' Rusinek <jakub rusinek gmail com
    <mailto:jakub rusinek gmail com>>:
     > do we need to support legacy cpu's by i386 compilation?
     > i586 would make fedora faster even 3 times.
     > difference is noticeable.

    .....
    where are your benchmarks for the "3 times faster" claim?
    the i386 packages are already optimized for newer cpus (mtune vs. march)
    where it makes sense to have i686 versions there are some (kernel,
    glibc)

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--
Jakub 'Livio' Rusinek
http://liviopl.jogger.pl/



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