Re: [RFC PATCH v1 8/8] sched/deadline: make bandwidth enforcement scale-invariant

Peter Zijlstra
2017-07-19T07:22:05Z

On Wed, Jul 05, 2017 at 09:59:05AM +0100, Juri Lelli wrote:
> @@ -1156,9 +1157,26 @@ static void update_curr_dl(struct rq *rq)
> if (unlikely(dl_entity_is_special(dl_se)))
> return;
>
> - if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM))
> - delta_exec = grub_reclaim(delta_exec, rq, &curr->dl);
> - dl_se->runtime -= delta_exec;
> + /*
> + * For tasks that participate in GRUB, we implement GRUB-PA: the
> + * spare reclaimed bandwidth is used to clock down frequency.
> + *
> + * For the others, we still need to scale reservation parameters
> + * according to current frequency and CPU maximum capacity.
> + */
> + if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
> + scaled_delta_exec = grub_reclaim(delta_exec,
> + rq,
> + &curr->dl);
> + } else {
> + unsigned long scale_freq = arch_scale_freq_capacity(cpu);
> + unsigned long scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
> +
> + scaled_delta_exec = cap_scale(delta_exec, scale_freq);
> + scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
> + }
> +
> + dl_se->runtime -= scaled_delta_exec;
>

This I don't get...