Re: [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks

Juri Lelli
2018-08-07T13:26:42Z

Hi,

On 06/08/18 17:39, Patrick Bellasi wrote:

[...]

> @@ -223,13 +224,25 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
> * utilization (PELT windows are synchronized) we can directly add them
> * to obtain the CPU's actual utilization.
> *
> - * CFS utilization can be boosted or capped, depending on utilization
> - * clamp constraints configured for currently RUNNABLE tasks.
> + * CFS and RT utilizations can be boosted or capped, depending on
> + * utilization constraints enforce by currently RUNNABLE tasks.
> + * They are individually clamped to ensure fairness across classes,
> + * meaning that CFS always gets (if possible) the (minimum) required
> + * bandwidth on top of that required by higher priority classes.

Is this a stale comment written before UCLAMP_SCHED_CLASS was
introduced? It seems to apply to the below if branch only.

> */
> - util = cpu_util_cfs(rq);
> - if (util)
> - util = uclamp_util(cpu_of(rq), util);
> - util += cpu_util_rt(rq);
> + util_cfs = cpu_util_cfs(rq);
> + util_rt = cpu_util_rt(rq);
> + if (sched_feat(UCLAMP_SCHED_CLASS)) {
> + util = 0;
> + if (util_cfs)
> + util += uclamp_util(cpu_of(rq), util_cfs);
> + if (util_rt)
> + util += uclamp_util(cpu_of(rq), util_rt);
> + } else {
> + util = cpu_util_cfs(rq);
> + util += cpu_util_rt(rq);
> + util = uclamp_util(cpu_of(rq), util);
> + }

Best,

- Juri