2019-12-12 04:12:59

by Thara Gopinath

Subject: [Patch v6 5/7] sched/fair: update cpu_capacity to reflect thermal pressure

cpu_capacity relflects the maximum available capacity of a cpu. Thermal
pressure on a cpu means this maximum available capacity is reduced. This
patch reduces the average thermal pressure for a cpu from its maximum
available capacity so that cpu_capacity reflects the actual
available capacity.

Signed-off-by: Thara Gopinath <[email protected]>
---
kernel/sched/fair.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e12a375..4840655 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7725,8 +7725,15 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
if (unlikely(irq >= max))
return 1;

+ /*
+ * avg_rt.util avg and avg_dl.util track binary signals
+ * (running and not running) with weights 0 and 1024 respectively.
+ * avg_thermal.load_avg tracks thermal pressure and the weighted
+ * average uses the actual delta max capacity.
+ */
used = READ_ONCE(rq->avg_rt.util_avg);
used += READ_ONCE(rq->avg_dl.util_avg);
+ used += READ_ONCE(rq->avg_thermal.load_avg);

if (unlikely(used >= max))
return 1;
--
2.1.4

2019-12-23 17:53:18

by Ionela Voinescu

Subject: Re: [Patch v6 5/7] sched/fair: update cpu_capacity to reflect thermal pressure

On Wednesday 11 Dec 2019 at 23:11:46 (-0500), Thara Gopinath wrote:
> cpu_capacity relflects the maximum available capacity of a cpu. Thermal
> pressure on a cpu means this maximum available capacity is reduced. This
> patch reduces the average thermal pressure for a cpu from its maximum

Maybe we can introduce two terms here: maximum possible capacity and
maximum currently available capacity.
I think using these two terms the message can become more clear:

cpu_capacity initially reflects the maximum possible capacity of a cpu
(capacity orig). Thermal pressure on a cpu means this maximum
possible capacity of a cpu is not available due to thermal events.
This patch subtracts the average thermal pressure for a cpu from the
cpu's maximum possible capacity so that cpu_capacity reflects the
actual maximum currently available capacity.

Kind regards,
Ionela.

> available capacity so that cpu_capacity reflects the actual
> available capacity.
>
> Signed-off-by: Thara Gopinath <[email protected]>
> ---
> kernel/sched/fair.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e12a375..4840655 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7725,8 +7725,15 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
> if (unlikely(irq >= max))
> return 1;
>
> + /*
> + * avg_rt.util avg and avg_dl.util track binary signals
> + * (running and not running) with weights 0 and 1024 respectively.
> + * avg_thermal.load_avg tracks thermal pressure and the weighted
> + * average uses the actual delta max capacity.
> + */
> used = READ_ONCE(rq->avg_rt.util_avg);
> used += READ_ONCE(rq->avg_dl.util_avg);
> + used += READ_ONCE(rq->avg_thermal.load_avg);
>
> if (unlikely(used >= max))
> return 1;
> --
> 2.1.4
>