Re: Possible CPUFreq governor

[Bruno Ducrot <ducrot@poupinou.org>]

On Wed, Apr 27, 2005 at 02:18:27PM -0400, Mark Bidewell wrote:
> It might help to explain how the governor is used. I have a user-mode
> daemon which samples the ACPI temperature every 2 seconds and communicates
> the speed at which non-interactive processes should be run via the sysfs
> interface.  The scheduler will then determine a processes interactivity
> and change the CPU speed accordingly.  In theory the processor could
> change speeds every process switch.

That why I have to do tests in case there is a lot of those process
switch but when modifiying max frequency instead.

> This governor is indeed similar to the ondemand governor.  The distinction
> is that while the ondemand governor expands CPU performance as load
> increases, tempscale must limit performance.  In my opinion, the ultimate
> solution would be a combination of the two governors.  That is, a governor
> which would react in the following way:
> 
> 1)  If the processor is idle, run at low speeds to conserve power (ondemand).
> 2)  Increase performance with demand as long a temperature is low (ondemand)
> 3)  If temperatures get to high, throttle compute-bound processes (tempscale)
> 
> I have done some limited experiments along this line using a user-mode
> daemon to switch governors (as well as speeds) between tempscale and
> ondemand as temperatures change.

That's why I suggest to touch max frequency, not the actual frequency.

This must be done outside a governor, so that you can have both actually.
I'll send you a patch after writing it for testing purpose so that you will
see what I have in mind.

-- 
Bruno Ducrot

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