Re: [RFC PATCH 06/16] arm: topology: Define TC2 sched energy and provide it to scheduler

On Sat, Jun 07, 2014 at 03:33:58AM +0100, Nicolas Pitre wrote:

On Fri, 6 Jun 2014, Ingo Molnar wrote:

quoted

In any case, even with turbo frequencies, switching power use is 
probably an order of magnitude higher than leakage current power use, 
on any marketable chip, so we should concentrate on being able to 
cover this first order effect (P/work ~ V^2), before considering any 
second order effects (leakage current).

Just so that people are aware... We'll have to introduce thermal 
constraint management into the scheduler mix as well at some point.  
Right now what we have is an ad hoc subsystem that simply monitors 
temperature and apply crude cooling strategies when some thresholds are 
met. But a better strategy would imply thermal "provisioning".

There is already work going on to improve thermal management:

http://lwn.net/Articles/599598/

The proposal is based on power/energy models (too). The goal is to
allocate power intelligently based on performance requirements.

While it is related to energy-aware scheduling and I fully agree that it
is something we need to consider, I think it is worth developing the two
ideas in parallel and look at sharing things like the power model later
once things mature. Energy-aware scheduling is complex enough on its
own to keep us entertained for a while :-)

Morten