On Mon, Jan 14, 2008 at 02:14:02PM -0600, Callum Lerwick wrote: > using OpenJPEG's MJ2 tools, I encode the speedway example using > "frames_to_mj2 -i Speedway.yuv -o Speedway.mj2 -I 1", then decode it. Which is about the most extreme case you will find. > So it is 0.54% *slower* when compiled for i586, which is unexpected and > strange, but such is gcc. I wouldn't expect much of a speed difference > compiling for i586, there was no major additions to the instruction set, > and we're already scheduling for modern processors. 586 has completely different scheduling pipelines wiht complex rules > Not quite "three times" faster, but 3.26% faster with i686. A major > addition to the i686 architecture was cmov, and gcc is actually very Current CPUs cmov is generally a lose. > both i386 and i686 versions. glibc and openssl already do this. Off the > top of my head, this would include Mesa, I know for a fact the majority Mesa already internally uses things like 3DNow. The Mesa folks would I'm sure welcome more optimised paths and cpu tuned variants. > all the help it can get. Not that the MPEG4 codecs are in Fedora > itself... MPEG4 is dominated by memory bandwidth so cache size is critical and FSB, not compiler options. Memory actually dominates most things today - and -Os is often the macro scale win -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
