Re: [gentoo-dev] Do we want optimal performance?

[Chris Gianelloni <wolf31o2@gentoo.org>]

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On Wed, 2004-09-08 at 06:15, Klavs Klavsen wrote:
> 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.

Gentoo is not all about performance.  While many of our users want to
squeeze the every drop of performance out of their systems, many use
Gentoo for any number of other reasons such as our philosophy, our
community, the manageability of portage, or even because they think
Larry the Cow just owns.

> 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 just want to ask where the manpower to do this will come from?  We
would have to start over with every CPU upgrade and every toolchain
upgrade.  It appears it would be an unending task of hours upon hours of
labor for each package.  Have you looked at the sheer number of CFLAGS
available?

> 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 see no problem with it provided you could find someone to actually do
the work.  This would be *very* boring work for most, which means it
would be abandoned by anyone but the most determined quite quickly.

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

Excellent.  Nothing is stopping you from doing exactly this on your own
machine, though, so go for it.

> 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.

Well, as soon as you enter in the possibility of user-defined
selections, then there is no point.  If we're going for optimal
performance, we shoot for optimal performance.  After all, with all this
test data who would know better, us, or each individual user who may or
may not have performed all the testing?

> 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.

You don't have to be a developer to get involved.  That is one of the
greatest things about Gentoo.

> 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.

While I agree that there can be great performance increases, I believe
that there is a definite trade-off between performance and
manageability.  This would be wholly unmanageable without an army of
testers working around the clock until Gentoo ceased to be... *grin*

-- 
Chris Gianelloni
Release Engineering - Operations/QA Manager
Games - Developer
Gentoo Linux

Is your power animal a penguin?

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