Re: Poor performance of G5 on GNOME's CPU benchmarks.

[Charles Plessy <plessy@debian.org>]

Le Sun, Aug 03, 2008 at 05:32:26PM +0200, Michel Dänzer a écrit :
> On Sun, 2008-08-03 at 11:53 +0900, Charles Plessy wrote:
> > 
> > The result is that on some particular types of computations, the G5
> > performs extremely bad: something like twice slower as an old 1.5 Ghz
> > Celeron machine. For some other tests, the performances of the
> > processors scale with the frequency.
> 
> Most likely, the x86 binaries tend to have optimizations for SSE/MMX
> whereas the powerpc binaries tend not to have VMX/Altivec optimizations.

Hi Michel,

Is it somthing that can be turned on, or does it require modifications
to the sources? Quoting a GCC webpage:

  "The interface is made available by including <altivec.h> and using
  -maltivec and -mabi=altivec."

http://gcc.gnu.org/onlinedocs/gcc/PowerPC-AltiVec-Built_002din-Functions.html

The case in which I saw the biggest difference if for the building of
the 'exonerate' package: it took 9 h on a bi-G5 2GHz, compared to 1 h 30
on the i386 buildd, 30 min on the alpha buildd, and > 30 h on the MIPS
buildds.

I am starting to wonder if some of the binaries we ship in Debian Med
for bioinformatic computation are useful on PowerPC. It must obviously
depend on what kind of calculation they are doing. Is there a way to
guess other than by benchmark?

Have a nice day,

-- 
Charles Plessy
Debian Med packaging team,
Tsurumi, Kanagawa, Japan