Re: [PATCH] cpufreq_ondemand

[Dominik Brodowski <linux@dominikbrodowski.de>]

On Wed, Oct 20, 2004 at 03:35:35AM -0400, Len Brown wrote:
> On Wed, 2004-10-20 at 01:03, Andre Eisenbach wrote:
> 
> > ... If the
> > speed steps down slowly but shoots up 100% quickly (as it is right
> > now), even a small task (like opening a folder, or scrolling down in a
> > document) will cause a tiny spike to 100% which takes a while to go
> > back down. The result is that the CPU spends most of it's time at 100%
> > or calming down. I wrote a small test program on my notebook which
> > confirms this.
> 
> The question is what POLICY we're trying to implement.

This is why there may be DIFFERENT policies a.k.a. governors in cpufreq.

>  If the goal is
> to to be energy efficient while the user notices no performance hit,
> then fast-up/slow-down is an EXCELLENT strategy.  But if the goal is to
> optimize for power savings at the cost of impacting performance, then
> another strategy may work better.

> The point is that no strategy will be optimal for all policies.  Linux
> needs a global power policy manager that the rest of the system can ask
> about the current policy.  This way sub-systems can (automatically)
> implement whatever local strategies are consistent with that global
> policy.

Put it in userspace, and let it ask the cpufreq core in the kernel to use a
specific governor or another depending on what you want. That's what certain
userspace daemons / scripts already do, btw.

	Dominik