My experience with cpufreq in -STABLE

[Bruno Ducrot]

On Wed, Apr 06, 2005 at 08:49:15AM +0200, Frank Behrens wrote:
> Bruno Ducrot <ducrot at poupinou.org> wrote on 4 Apr 2005 19:17:
> > You may start looking at src/usr.sbin/powerd in -current, and improve it
> > a bit?  The actual algorithm used in powerd may need some rework IMHO.
> 
> Which problems do you see?

powerd use an exponentional decrease of the frequency.  This might be
not stable for certain workload.

> My comments:
> 1. If the frequency is raised it should not go down immediately on 
> short idle phases. To raise the frequency the current idle value 
> should used but to lower the frequency we should calculate a weighted 
> idle average value.

It might be a solution.  It has been tested in that paper:

http://www-mtl.mit.edu/research/icsystems/pubs/conferences/2001/sinha_vlsi2001.pdf

and it seems it's maybe not the better one, though (search 'MAW', its
exactly what you suggest).

> 2. The default polling time of 500 ms seems to be very short. It can 
> increased to several seconds.

Problem if you increase teh polling intervall is that you can't be sure
that the system can detect in time when going up.

-- 
Bruno Ducrot

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.