Re: [linux-pm] [PATCH 0/2] RFC: CPU frequency max as PM QoS param

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday, February 28, 2012, Antti P Miettinen wrote:
> Adding people that were part of the thread in the beginning..
> 
> mark gross <markgross@thegnar.org> writes:
> > On Mon, Feb 27, 2012 at 04:04:00PM +0100, Antti Miettinen wrote:
> >> To the lists too..
> >> 
> >> On 02/27/2012 04:49 PM, Kevin Hilman wrote:
> >> > mark gross <markgross@thegnar.org> writes:
> >> >
> >> >  >> Current QoS settings could be thought of as performance constraints
> >> >  >> too. It's just that they determine minimum performance. Adding
> >> >  >> constraints for maxium performance is not a big stretch in my mind.
> >> >  >
> >> >  > Its not a big stretch to me either. I just think its a bit of a hack
> >> >  > and there is a bigger more interesting issue getting overlooked.
> >> >  >
> >> >  > Lastly why not simply make cpufreq thermal aware and talk directly to
> >> >  > it if you even need too?
> >> >
> >> > In fact, making a thermal framework "cooling device" that talks directly
> >> > to CPUfreq is already what's being done by the Linaro PMWG folks.
> >> >
> >> > The problem is that CPUfreq only controls the CPU frequency.
> >> >
> >> > There are other devices that could be scaled back to reduce heat as well
> >> > (DSP, and especially GPU), so having a more generic per-device
> >> > constraint interface that can cap the frequency for *any* scalable
> >> > device is a better framework IMO.
> >> >
> >> > It just so happens that pm_qos is already a good per-device constraint
> >> > framework and can easily modified to cap performance as well as request
> >> > a minimum performance.
> >> >
> >> > Kevin
> >
> > ok I'll stop trying to block it.
> >
> > I want to re-do the whole works anyway.  If this helps in the mean time
> > then go for it.
> 
> Great :-)
> 
> So what do other people think? Could we merge global CPU frequency
> constraints for now?

Not without an ACK from Dave (the cpufreq maintainer), that's for sure.

> I agree that more work is needed for e.g. per CPU constraints, user
> space interface and more complete thermal management. Actually for
> future I think the constraints could also become more general than just
> min/max "reduction operators". For e.g. core online status you might
> want union/intersection of bitmaps. Also, the more complete thermal
> management is related to load management in general (power budgeting for
> other reasons than just thermal).

Then perhaps let's not merge "temporary" stuff and figure out how to
implement what we _really_ want.

Thanks,
Rafael