Re: [PATCH v3 08/14] sched/core: uclamp: extend cpu's cgroup controller

Dietmar Eggemann
2018-08-17T12:21:38Z

On 08/06/2018 06:39 PM, Patrick Bellasi wrote:

[...]

> Give the above mechanisms, it is now possible to extend the cpu
> controller to specify what is the minimum (or maximum) utilization which
> a task is expected (or allowed) to generate.
> Constraints on minimum and maximum utilization allowed for tasks in a
> CPU cgroup can improve the control on the actual amount of CPU bandwidth
> consumed by tasks.

I assume this is covered by the s/bandwidth/capacity/ you had w/ Juri on
01/14.

[...]

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ff76b000bbe8..2ba55a4afffb 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1211,6 +1211,74 @@ static inline void uclamp_group_get(struct task_struct *p,
> uclamp_group_put(clamp_id, prev_group_id);
> }
>
> +#ifdef CONFIG_UCLAMP_TASK_GROUP
> +/**
> + * init_uclamp_sched_group: initialize data structures required for TG's
> + * utilization clamping
> + */
> +static inline void init_uclamp_sched_group(void)
> +{
> + struct uclamp_map *uc_map;
> + struct uclamp_se *uc_se;
> + int group_id;
> + int clamp_id;
> +
> + /* Root TG's is statically assigned to the first clamp group */
> + group_id = 0;
> +
> + /* Initialize root TG's to default (none) clamp values */
> + for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
> + uc_map = &uclamp_maps[clamp_id][0];
> +
> + /* Map root TG's clamp value */
> + uclamp_group_init(clamp_id, group_id, uclamp_none(clamp_id));
> +
> + /* Init root TG's clamp group */
> + uc_se = &root_task_group.uclamp[clamp_id];
> + uc_se->value = uclamp_none(clamp_id);
> + uc_se->group_id = group_id;
> +
> + /* Attach root TG's clamp group */
> + uc_map[group_id].se_count = 1;
> + }
> +}

Can you not save some lines here:

static inline void init_uclamp_sched_group(void)
{
- struct uclamp_map *uc_map;
struct uclamp_se *uc_se;
int group_id;
int clamp_id;
@@ -1228,8 +1227,6 @@ static inline void init_uclamp_sched_group(void)

/* Initialize root TG's to default (none) clamp values */
for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
- uc_map = &uclamp_maps[clamp_id][0];
-
/* Map root TG's clamp value */
uclamp_group_init(clamp_id, group_id,
uclamp_none(clamp_id));

@@ -1239,7 +1236,7 @@ static inline void init_uclamp_sched_group(void)
uc_se->group_id = group_id;

/* Attach root TG's clamp group */
- uc_map[group_id].se_count = 1;
+ uclamp_maps[clamp_id][group_id].se_count = 1;
}

This would also make uclamp_group_available() smaller. …