[MPlayer-dev-eng] Re: Vorbis decoding performance

[Michael Niedermayer]

Hi

On Thu, Aug 17, 2006 at 10:32:44AM -0400, Rich Felker wrote:
> On Mon, Aug 07, 2006 at 11:09:45PM +0200, Michael Niedermayer wrote:
> > Hi
> > 
> > On Mon, Aug 07, 2006 at 08:22:59PM +0200, Aurelien Jacobs wrote:
> > > On Wed, 02 Aug 2006 17:38:07 +0200
> > > Baptiste Coudurier <baptiste.coudurier at smartjog.com> wrote:
> > > 
> > > > Hi
> > > > 
> > > > Uoti Urpala wrote:
> > > > > On Wed, 2006-08-02 at 11:21 +0200, Diego Biurrun wrote:
> > > > >> I sat down and did some benchmarks on my K6-III 500, Debian stable
> > > > > 
> > > > 
> > > > Comparison on p4 2.4ghz, debian unstable:
> > > 
> > > Some more benchmark.
> > > Target: ARM (Xscale IXP420 266MHz gcc-4.1)
> > > 
> > > ./mplayer -quiet -benchmark -ao pcm:fast:file=/dev/null song37.ogg
> > > BENCHMARKs: VC:   0.000s VO:   0.000s A: 257.712s Sys:   0.657s =  258.369s
> > > BENCHMARK%: VC:  0.0000% VO:  0.0000% A: 99.7456% Sys:  0.2544% = 100.0000%
> > > 
> > > ./mplayer -quiet -benchmark -afm ffmpeg -ao pcm:fast:file=/dev/null song37.ogg
> > > ... still running... (more than an hour)
> > 
> > hmm floating point emulation is slow sure but it shouldnt be that slow ...
> 
> Why not? At least Nx slower should be expected where every (1-cycle)
> opcode becomes a N-cycle invalid opcode fault and context switch to
> kernelspace handler. I would expect N is somewhere between 200 and
> 5000.

well, for some reason i thought that the compiler should not generate invalid
opcodes to begin with but rather inline / call the emu code ...
and keep in mind that some cpu architectures have no fp-opcodes at all, so
gcc should be able to do that, but then again ive not looked at what gcc
really does on architectures without fpu or what it doess when the cpu
type specified has no fpu but the architectures has ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is