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SubjectRe: [Patch v8 4/7] sched/fair: Enable periodic update of average thermal pressure
On Fri, Jan 17, 2020 at 11:40:45AM +0000, Quentin Perret wrote:
> On Thursday 16 Jan 2020 at 16:15:02 (+0100), Peter Zijlstra wrote:
> > > @@ -10275,6 +10281,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
> > > {
> > > struct cfs_rq *cfs_rq;
> > > struct sched_entity *se = &curr->se;
> > > + unsigned long thermal_pressure = arch_cpu_thermal_pressure(cpu_of(rq));
> > >
> > > for_each_sched_entity(se) {
> > > cfs_rq = cfs_rq_of(se);
> > > @@ -10286,6 +10293,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
> > >
> > > update_misfit_status(curr, rq);
> > > update_overutilized_status(task_rq(curr));
> > > + update_thermal_load_avg(rq_clock_task(rq), rq, thermal_pressure);
> > > }
> >
> > I'm thinking this is the wrong place; should this not be in
> > scheduler_tick(), right before calling sched_class::task_tick() ? Surely
> > any execution will affect thermals, not only fair class execution.
>
> Right, but right now only CFS takes action when we overheat. That is,
> only CFS uses capacity_of() which is where the thermal signal gets
> reflected.

Sure, but we should still track the thermals unconditionally, even if
only CFS consumes it.

> We definitely could (and maybe should) make RT and DL react to thermal
> pressure as well when they're both capacity-aware. But perhaps that's
> for later ? Thoughts ?

Yeah, that's later head-aches. Even determining what to do there, except
panic() is going to be 'interesting'.

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