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SubjectRe: [Patch v6 4/7] sched/fair: Enable periodic update of average thermal pressure
On Wed, Dec 11, 2019 at 11:11:45PM -0500, Thara Gopinath wrote:
> Introduce support in CFS periodic tick and other bookkeeping apis
> to trigger the process of computing average thermal pressure for a
> cpu. Also consider avg_thermal.load_avg in others_have_blocked
> which allows for decay of pelt signals.
>
> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
> ---
> kernel/sched/fair.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> v4->v5:
> - Updated both versions of update_blocked_averages to trigger the
> process of computing average thermal pressure.
> - Updated others_have_blocked to considerd avg_thermal.load_avg.
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 08a233e..e12a375 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7462,6 +7462,9 @@ static inline bool others_have_blocked(struct rq *rq)
> if (READ_ONCE(rq->avg_dl.util_avg))
> return true;
>
> + if (READ_ONCE(rq->avg_thermal.load_avg))
> + return true;
> +
> #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
> if (READ_ONCE(rq->avg_irq.util_avg))
> return true;
> @@ -7487,6 +7490,7 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
> {
> const struct sched_class *curr_class;
> u64 now = rq_clock_pelt(rq);
> + unsigned long thermal_pressure = arch_scale_thermal_capacity(cpu_of(rq));
> bool decayed;
>
> /*
> @@ -7497,6 +7501,8 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
>
> decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
> update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
> + update_thermal_load_avg(rq_clock_task(rq), rq,
> + thermal_pressure) |
> update_irq_load_avg(rq, 0);
>
> if (others_have_blocked(rq))
> @@ -10263,6 +10269,7 @@ 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_scale_thermal_capacity(cpu_of(rq));
>
> for_each_sched_entity(se) {
> cfs_rq = cfs_rq_of(se);
> @@ -10274,6 +10281,7 @@ 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);
> }

My objection here is that when the arch does not have support for it,
there is still code generated and runtime overhead associated with it.

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