Messages in this thread | | | Date | Fri, 17 Aug 2018 12:04:21 +0100 | From | Patrick Bellasi <> | Subject | Re: [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting |
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On 06-Aug 17:39, Patrick Bellasi wrote:
[...]
> +/** > + * uclamp_cpu_get_id(): increase reference count for a clamp group on a CPU > + * @p: the task being enqueued on a CPU > + * @rq: the CPU's rq where the clamp group has to be reference counted > + * @clamp_id: the utilization clamp (e.g. min or max utilization) to reference > + * > + * Once a task is enqueued on a CPU's RQ, the clamp group currently defined by > + * the task's uclamp.group_id is reference counted on that CPU. > + */ > +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; > + > + /* No task specific clamp values: nothing to do */ > + group_id = p->uclamp[clamp_id].group_id; > + if (group_id == UCLAMP_NOT_VALID) > + return;
This is broken for util_max aggression.
By not refcounting tasks without a task specific clamp value, we end up enforcing a max_util to these tasks when they are co-scheduled with another max clamped task.
I need to fix this by removing this "optimization" (working just for util_min) and refcount all the tasks.
> + > + /* Reference count the task into its current group_id */ > + uc_grp = &rq->uclamp.group[clamp_id][0]; > + uc_grp[group_id].tasks += 1; > + > + /* > + * 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. > + */ > + uc_cpu = &rq->uclamp; > + clamp_value = p->uclamp[clamp_id].value; > + if (uc_cpu->value[clamp_id] < clamp_value) > + uc_cpu->value[clamp_id] = clamp_value; > +} > +
-- #include <best/regards.h>
Patrick Bellasi
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