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Re: multi-media packages/gcc/latest CPU optimizations



On 31/05/09 08:51, RS wrote:
I'd like to understand how some of the multi-media packages are compiled
for distros to make maximum effective use of the latest CPU features
(SSE4,multi-core,large L2/L3 caches etc)
You can take a look at the specs that are used to compile and package the apps eg: (since the apps you mention aren't in Fedora)
http://cvs.rpmfusion.org/viewvc/rpms/?root=free

Then you might need to read the make files for each app you are interested in, to see what compiler options are passed. Or read an rpmbuild log, to see which parameters are passed to the compiler:
http://buildsys.rpmfusion.org/plague-results/

I understand pkgs are compiled assuming i386 (or i686?) to cover the
vast majority of PC's out there.
In Fedora 11, the minimum CPU is i586.

For packages like
vlc,mplayer
Uses the ffmpeg library

,dvd::rip
Rip speed is about drive/bus speed. Format conversion, and decode recompression are about the library used (ffmpeg ?) Dominic has played with the flags a bit, you might find some interesting reading in the RPM Fusion mailing list archives.

? are
there specific GCC/runtime optimizations that yield "real world"
performance.
Do you mean real-world performance improvements ?
That don't have other side affects ?
Remember that selinux is watching over executable actions, and gcc hardening and packaging compilation requirements relating to required option flags also come into play. Fedora uses certain flags to ensure that correct debuginfo is produced, and to avoid bugs introduced due to excessive optimization.

? I have a bunch of
PC's at home (Phenom II X4, Core 2 Quad and a new Core i7 that is being
Assuming you use an x86_64 kernel and packages, then they are optimised for the earliest model in the group / the most common processors found.

If you look at a system usage point of view (eg gkrellm) where you can see CPUs, disks/partition and network use at once, what seems to be the bottleneck ?
Perhaps lack of multi-threaded apps ?

Unfortunately, I believe pulseaudio to waste CPU power, eg on an older athlon xp 2000, playing mp3 files takes about 40-45% CPU; this doesn't leave much for mpeg2 decoding of a video. This only took 5% CPU before pulseaudio.

That should get some opinions started.

Cheers,

DaveT.


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