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

Thomas Gleixner
2015-11-20T09:46:09Z

On Thu, 19 Nov 2015, Peter Zijlstra wrote:
> On Thu, Nov 19, 2015 at 05:24:07PM +0000, Morten Rasmussen wrote:
> > I would consider it an
> > emergency-only mechanism (as in emergency brake) that isn't really
> > suitable for normal thermal management. In which case: Does this sort of
> > mechanism belong in the scheduler code?
>
> I would prefer it not to be, but Thomas is very much opposed to teaching
> the nohz code to 'work' on !idle threads.

The whole concept of faking idle is simply crap.

If you want to avoid that stuff in the scheduler, then create a
mechanism which just defers the next timer interrupt for X
milliseconds and does not any fiddling with NOHZ state and such.

That might hurt RT tasks, but if someone really cares about real-time
and deterministic behaviour, then running the machine on its thermal
limits is simply stupid. In fact any sensible RT system will bring
itself into a safe state way before the machine runs into that
condition.

Thanks,

tglx