Optimizations.

[Wes Peters]

On Thursday 15 May 2003 14:38, Poul-Henning Kamp wrote:
> In message <20030516002105.K40030-100000 at haldjas.folklore.ee>, Narvi 
writes:
> >On Thu, 15 May 2003, Marcel Moolenaar wrote:
> >> On Thu, May 15, 2003 at 02:30:33PM +0200, Pawel Jakub Dawidek wrote:
> >> > Maybe is time to think about some 'optimiztion team' creation?
> >>
> >> I think I don't want to see this happen based on professional
> >> experience.
> >
> >Well, supposedly any such team would need to start by creating a set
> > of tools and benchmarks [...]
>
> If I have to be honest, I think this is the wrong way to approach the
> subject, if on no other ground than on the 3. rule of optimizations
> ("Don't do it yet").
>
> While it would be nice to have a set of "blessed benchmarks" canned
> and ready to run, we should learn from the lmbench fiasco in Linux
> that such benchmarks can easier mislead than lead.
>
> My personal professional experience with optimizations or "Performance
> management" as it was called, is that you want some very rigid
> _functional_ testcases, which must pass at any one time so you don't
> unnoticed loose functionality to optimizations.

The best class of optimizations that can be made is fundamental 
algorithmic efficiency, rather than micro-optimizing poorly written code.

> We also know that the main performance issue is Giant, Giant and Giant.

Embracing and learning the locking code, then helping with the lock 
pushdown task, would be a worthwhile goal for some junior kernel hackers.  
It would also be a great learning experience.

> So I really think the band of merry men we are talking about, if they
> can be interested, would do much more good if they would start out
> building functional and regression tests for our most critical
> facilities.
>
> I can't speak for the other heavy-duty guys in the project, but I
> would personally be _really_ _REALLY_ grateful if I could "cd
> /usr/src ; make test" and know that a significant fraction of our
> functionality worked if it returned a zero exit code.

Yes, yes, and yes.  Please note, folks, that this is coming from one of 
the few developers to bothers to implement test cases for his own code.

-- 

        Where am I, and what am I doing in this handbasket?

Wes Peters                                               wes at softweyr.com