RFC: powerd algorithms enhancements

[Cyrille Szymanski]

2008/11/11 Alexander Motin <mav at freebsd.org>:
> Universality and predictiveness. Systems with 2 and with 32 levels will
> drop/rise frequency with same absolute rate. If we are trying to speak about
> some comparing, algorithm should be hardware independent.

Hi

The heuristics PAST and FLAT are two examples of strategies which do
just this : they determine the desired operating frequency (in Hz) and
then switch to the closest level available.

>> There's a patch Cyrille Szymanski has sent me to review that implements
>> the FLAT and PAST algorithms in powerd.  I think we should not add new
>> modes that are heuristics (including this one) until we have a chance to
>> compare it to algorithms that have been the result of real research.
>
> So show it to us. This area is heuristic by default as there is several
> opposite criteriums, so any algorithm will be heuristic.

Although I see the benefits of your proposal, and reckon that systems
with may levels are more and more common these days. The point is, I
think, to avoid adding tuning knobs to powerd that would be too
specific to your configuration and which might benefit everyone.
Research will (I hope) indicate the way to go.

Thanks !
-- 
Cyrille Szymanski