Re: Power Management framework proposal

[david@lang.hm]

On Tue, 24 Jul 2007, Benjamin Herrenschmidt wrote:

> On Sun, 2007-07-22 at 10:26 -0700, Arjan van de Ven wrote:
> > On Sat, 2007-07-21 at 23:49 -0700, david@lang.hm wrote:
> >
> > > this approach would allow the transition of ALL drivers to the new mode of
> > > operation in one fell swoop, and then adding additional power management
> > > features is just adding to the existing list rather then implementing new
> > > functions.
> >
> >
> > I have a concern with this approach though. It seems to assume that
> > there is one global thing somewhere that sets the system state; in my
> > experience that is the wrong approach; in fact there is a very definite
> > evidence that there are many decisions on power that are to be made
> > local at a high frequency. An example of this is the processor speed;
> > the ondemand governer does exactly this for the cpus that can switch
> > speeds fast; it's just impossible to beat such a local, fast decision
> > with anything on a global scale.
> >
> > On the other hand, some things (the high level goals and constraints)
> > are obviously global.
>
> I think we need a set of constraints that trickle down the power tree
> and limit what a given driver can do locally.

what sort of contraints are you thinking of?

David Lang
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