powerd effectiveness

[Bruno Ducrot]

On Fri, Jan 13, 2006 at 10:10:51AM +1030, Daniel O'Connor wrote:
> On Fri, 13 Jan 2006 00:10, Bruno Ducrot wrote:
> > > Thats the correct one, it is 75mhz. I was suspecting hardwares
> > > limitations in terms of modulating the frequency quickly enough. Just
> > > wanted to make sure.
> >
> > What you have noticed is acpi_throttle(4).  The combinaison of
> > some VIA chipset and AMD processors give 16 frequencies.
> > powerd(8) is not designed for thermal stuff, and will never be.
> > It's up to acpi_thermal(4) to cool the processor if needed.
> >
> > Note that I think acpi_throttle(4) can only be used for cooling a
> > processor. I don't think it is usefull for power comsuption at all for
> > which
> > powerd(4) is designed.  Some other people may have different opinion of
> > course.
> 
> I don't see how reducing power consumption could NOT affect the temperature.
> 
> Nearly all of the energy going into the CPU is disipated as heat.

Of course.  But the goal of powerd is to reduce power comsuption with
nearly no visible impact on performance.  This imply that if the
runpercent is nearly 100%, then the processor will be put to full
frequency even though this can imply an overheat situation.
The role of acpi_thermal is to reduce frequency if the processor is
too hot, and this imply performance loss if runpercent is high.

> > You may also want to check if sysutlis/fvcool can help you if setting
> > the above sysctl is not possible (but don't mix the two).
> 
> How come?
> (I am just curious :)
> 
> -- 
> Daniel O'Connor software and network engineer
> for Genesis Software - http://www.gsoft.com.au
> "The nice thing about standards is that there
> are so many of them to choose from."
>   -- Andrew Tanenbaum
> GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C



-- 
Bruno Ducrot

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