multi-media packages/gcc/latest CPU optimizations

[David Timms]

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.