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

[Antti P Miettinen <amiettinen@nvidia.com>]

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?

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).

	--Antti