Re: [Patch v5 4/6] sched/fair: update cpu_capcity to reflect thermal pressure

[Amit Kucheria]

On Wed, Nov 6, 2019 at 12:20 AM Thara Gopinath
<thara.gopinath@xxxxxxxxxx> wrote:
>
> cpu_capacity relflects the maximum available capacity of a cpu. Thermal

s/relflects/reflects

> 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.
>
> Other signals that are deducted from cpu_capacity to reflect the actual
> capacity available are rt and dl util_avg. util_avg tracks a binary signal
> and uses the weights 1024 and 0. Whereas thermal pressure is tracked
> using load_avg. load_avg uses the actual "delta" capacity as the weight.

Consider rephrasing as,

Currently, effective cpu capacity is calculated by deducting RT and DL
average utilization (util_avg) from cpu_capacity. For thermal
pressure, we use load_avg instead of util_avg which is a binary signal
(0 or 1024) because <put why here>


> Signed-off-by: Thara Gopinath <thara.gopinath@xxxxxxxxxx>
> ---
>  kernel/sched/fair.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9fb0494..5f6c371 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7738,6 +7738,7 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
>
>         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
>