Re: [PATCH v4 03/16] sched/core: uclamp: add CPU's clamp groups accounting

Peter Zijlstra
2018-09-13T19:12:31Z

On Tue, Aug 28, 2018 at 02:53:11PM +0100, Patrick Bellasi wrote:
> +static inline void uclamp_cpu_get_id(struct task_struct *p,
> + struct rq *rq, int clamp_id)
> +{
> + struct uclamp_group *uc_grp;
> + struct uclamp_cpu *uc_cpu;
> + int clamp_value;
> + int group_id;
> +
> + /* Every task must reference a clamp group */
> + group_id = p->uclamp[clamp_id].group_id;

> +}
> +
> +static inline void uclamp_cpu_put_id(struct task_struct *p,
> + struct rq *rq, int clamp_id)
> +{
> + struct uclamp_group *uc_grp;
> + struct uclamp_cpu *uc_cpu;
> + unsigned int clamp_value;
> + int group_id;
> +
> + /* New tasks don't have a previous clamp group */
> + group_id = p->uclamp[clamp_id].group_id;
> + if (group_id == UCLAMP_NOT_VALID)
> + return;

*confused*, so on enqueue they must have a group_id, but then on dequeue
they might no longer have?

> +}

> @@ -1110,6 +1313,7 @@ static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
> if (!(flags & ENQUEUE_RESTORE))
> sched_info_queued(rq, p);
>
> + uclamp_cpu_get(rq, p);
> p->sched_class->enqueue_task(rq, p, flags);
> }
>
> @@ -1121,6 +1325,7 @@ static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
> if (!(flags & DEQUEUE_SAVE))
> sched_info_dequeued(rq, p);
>
> + uclamp_cpu_put(rq, p);
> p->sched_class->dequeue_task(rq, p, flags);
> }

The ordering, is that right? We get while the task isn't enqueued yet,
which would suggest we put when the task is dequeued.