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Re: kernel module options for cpufreq



On Mon, 2008-06-30 at 09:10 +0200, Adam Tkac wrote:
> On Fri, Jun 27, 2008 at 05:13:24PM +0100, Richard Hughes wrote:
> > * remove ´╗┐CONFIG_CPU_FREQ_GOV_POWERSAVE -- ondemand automatically
> > throttles down to lowest, and is just a hardcoded state
> 
> I don't think removal of powersave governor is good idea. Generally
> ondemand governor does great job but in some cases doesn't. For
> example when I play some films in mplayer ondemand sets frequency to
> max which is not needed, of course.

Right, so we need to fix ondemand to be cleverer.

> Powersave governor is also good in case that you have bad fan in your
> laptop and you are going to compile some big source. Without powersave
> it is not possible (yes, it really happens :) )

Right, thermal management is similar to power management for the action
but not for the policy. I don't think forcing the lowest speed setting
is the correct way to fix this. If the laptop is running cool, why use
the slowest speed?

> > Matthew Garrett and I are working on a latency profile for power
> > management, and having all these modules potentially loaded is bad.
> > 
> > Comments?
> > 
> 
> I think we should preserve ondemand and powersave governors (and
> potentialy others as Dave Jones wrote in this thread). Please don't
> drop them in favour of your project which might be generally better but
> I believe there are cases where current governors are better.

Right, cheers for your feedback. In view of everybodies comments, what
about the following:

* Compile _into_ the kernel ondemand, performance, powersave and
userspace.
* Default to performance in the kernel rather than userspace
* Build as a module conservative with the view of just fixing ondemand
if there are any special use-cases that conservative is better at
* Export the P and C state latency to userspace and let the system
policy dictate the governor. For instance, even for machines that have a
long latency for changing P states should be able to use ondemand if we
want to save maximum power.

How does that sound?

Richard.



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