Re: A simple cpufreq(9)

[David Young <dyoung%pobox.com@localhost>]

On Fri, Sep 30, 2011 at 06:19:44AM +0300, Jukka Ruohonen wrote:
> > It seems that ultimately we need an API for telling a power-savings goal
> > and constraints (latency, throughput, battery life, the screen isn't too
> > dark to read) for the system to meet.  Do you hope for someone to build
> > that into the kernel on top of cpufreq(9)?
> 
> Not really; as I've written before, my opinion is that most of this should
> be in the user space. The CPU PM is an exception for obvious reasons. There
> could be a more involved API for cpu_idle(9) though (cf [1]).

I don't think that the division of responsibility for power management
between kernel & userland is obvious.

How do you hope for cpufreq(9) to be used?

While reading the API and discussion, it occurred to me that if
cpufreq(9) is chiefly used for making power/performance trade-offs,
maybe the API should be concerned with the goal (power savings) instead
of an independent variable (frequency).  Then maybe you can use one
API---cpupm(9)?---to set the objective, and let the implementation
choose the variables (C-state, P-state, frequency) to tweak.

Dave

-- 
David Young             OJC Technologies is now Pixo
dyoung%pixotech.com@localhost     Urbana, IL   (217) 344-0444 x24