Re: [RFC PATCH v1 0/3] Saving power by cpu evacuation using sched_mc=n

[Ingo Molnar <mingo@elte.hu>]

* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> > > Also, the user interface should be that single thermal 
> > > capacity knob, more fine grained control is undesired.
> > 
> > For power savings, a single evacuation knob will do.  While for 
> > thermal we will need additional parameters to choose the right 
> > cores to evacuate.  Some sort of directional/vector parameter.
> 
> Why? are machines that non-uniform in cooling capacity that it 
> really matters which core generates the heat? Sounds like badly 
> designed hardware to me.
> 
> I would expect it to only be the total head generated/power taken 
> from the rack unit.

If we add thermal throttling at the kernel level then a single knob 
(with a percentile-ish unit) is probably the furthest we will go - 
with "not doing it at all" still being the other, very tempting 
alternative.

If the only technical way you can find to do it is via myriads of 
non-intuitive knobs and per core settings - then the answer is 
really 'no thanks'.

	Ingo