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SubjectRe: [PATCH 1/7] sched/core: uclamp: add CPU clamp groups accounting
On Mon, Apr 09, 2018 at 05:56:09PM +0100, Patrick Bellasi wrote:
> +static inline void uclamp_cpu_get(struct task_struct *p, int cpu, int clamp_id)
> +{
> + struct uclamp_cpu *uc_cpu = &cpu_rq(cpu)->uclamp[clamp_id];
> + int clamp_value;
> + int group_id;
> +
> + /* Get task's specific clamp value */
> + clamp_value = p->uclamp[clamp_id].value;
> + group_id = p->uclamp[clamp_id].group_id;
> +
> + /* No task specific clamp values: nothing to do */
> + if (group_id == UCLAMP_NONE)
> + return;
> +
> + /* Increment the current group_id */

That I think qualifies being called a bad comment.

> + uc_cpu->group[group_id].tasks += 1;
> +
> + /* Mark task as enqueued for this clamp index */
> + p->uclamp_group_id[clamp_id] = group_id;

Why exactly do we need this? we got group_id from @p in the first place.

I suspect this is because when we update p->uclamp[], we don't update
this active value (when needed), is that worth it?

> + /*
> + * If this is the new max utilization clamp value, then we can update
> + * straight away the CPU clamp value. Otherwise, the current CPU clamp
> + * value is still valid and we are done.
> + */
> + if (uc_cpu->value < clamp_value)
> + uc_cpu->value = clamp_value;
> +}

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