Re: [PATCH 3/4] sched: introduce synchronized idle injection

[Arjan van de Ven <arjan@linux.intel.com>]

On 11/18/2015 7:44 AM, Morten Rasmussen wrote:
> I would not necessarily want to punish all cpus
> system-wide if we have local overheating in one corner. If would rather
> have it apply to only the overheating socket in a multi-socket machine
> and only the big cores in a big.LITTLE system.

most of the time thermal issues aren't inside the SOC, but on a system level
due to cheap heat spreaders or outright lack of space due to thinness. But
even if you have one part of the die too hot:

For core level idle injection, no need to synchronize that; the reason to synchronize
is generally that when ALL cores are idle, additional power savings kick in
(like memory going to self refresh, fabrics power gating etc); those additional
power savings are what makes this more efficient than just voltage/frequency
scaling at the bottom of that range...   not so much the fact that things are just idle.