[gentoo-dev] Do we want optimal performance?

["Klavs Klavsen" <kl@vsen.dk>]

Hi guys,

Just read an interesting article about Xeon vs. Opteron from anandtech -
where they really show how much difference compile optimizations (or not)
does - and how it differs for different programs for different processors.

http://www.anandtech.com/linux/showdoc.aspx?i=2163&p=1

To me this clearly shows, that if Gentoo wants the best performance - we
can't use a "one cflags fits them all" approach. I do know that if a
program breaks, those CFLAGS are pulled out in the individual ebuild, but
this is not due to poor performance.

IMHO the only way for Gentoo to prove its true potential - is to somehow
build an array of compile options, with CPU's on X, programs on Y and
GCC-version on Z. Getting the numbers for each CPU, will ofcourse require
writing tests, for each program - but IMHO this can be done, if we do it
one at a time.

I would suggest these tests be included like the gentoo-stats program, as
something the individual Gentooist can choose to run after each compile -
which would give him the optimal performance (and recompile X number of
times to test different flags out) on his CPU/program/GCCversion
combination, and at the same time, send the result to a Gentoo database.

I know I would definetely have the patience to let it test and test again,
if it meant more performance for me Smile

The end result should be, that Gentoo automagically selects the optimal
CFLAGS (in performance and stability - perhaps with some optimizations
flagged as "unstable" so people can select "optimize for performance" vs.
"optimize for stability") depending on the X, Y and Z from above.

I would very much like to be one of the guys that gets the ball rolling,
but as I'm not a Gentoo Dev - We (or just I) need to agree with the Gentoo
Dev's on how this could best be done.

What do you think? am I crazy? It seems to me that the anandtech tests
shows that it is more than just a 1% or 2% difference, with the right
CFLAGS - and that the right CFLAGS for one program, can be the worst for
another on same CPU/GCC combination.


-- 
Regards,
Klavs Klavsen, GSEC - kl@vsen.dk - http://www.vsen.dk
PGP: 7E063C62/2873 188C 968E 600D D8F8  B8DA 3D3A 0B79 7E06 3C62

"Those who do not understand Unix are condemned to reinvent it, poorly."
  --Henry Spencer


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