RPM Builds and System Optimization

Alexander Dalloz alexander.dalloz at uni-bielefeld.de
Thu Aug 26 16:40:31 UTC 2004


Am Do, den 26.08.2004 schrieb David Cary Hart um 18:26:

> Most of the Fedora RPMS are provided as i386. These can easily be
> recompiled as:
> 
> rpmbuild --target i686 --rebuild package.src.rpm
> 
> a. Is it worth it? In other words, is there really a performance gain in
> packages like - say - KDE?

Mostly not.

This is an alway returning question, asked time by time. The RPMs of
Fedora Core are build for arch i386 with optimization enabled for P4
CPU. So they are able to run on all i386 platform and will use special
instructions on newer CPUs.

If you count the time to proceed the custom compilation it is not worth
the efforts.

> b. Assuming that I installed the RPM sources and built from the spec
> file, as long as I am at it, could I also benefit by changing some of
> the FLAGS?
> 
> 	For example:
> 		CHOST="i686-pc-linux-gnu"
> 		CFLAGS="-march=pentium4 -O3 -pipe -fomit-frame-pointer"

This is the "Gentoo geek factor". The compilation for P4 architecture
does not increase anything significantly but makes packages incompatible
to other CPUs. The -O3 flags does not mean better optimization than -O2
and thus better performance in general. -O3 does not mean better, but
can make things worse.

If you have too much time, then I suggest you spent it to help in
development making Fedora even better ;)

Alexander


-- 
Alexander Dalloz | Enger, Germany | GPG key 1024D/ED695653 1999-07-13
Fedora GNU/Linux Core 2 (Tettnang) kernel 2.6.8-1.521smp 
Serendipity 18:33:12 up 6 days, 14:15, load average: 1.15, 1.15, 1.17 
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