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

Patrick Bellasi
2018-08-17T14:24:23Z

On 17-Aug 14:21, Dietmar Eggemann wrote:
> 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.

Yes... I need to update this changelog too.

> [...]
>
> >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.

Unfortunately this var name and its matrix indexes tends to become
quite long easily and in some usages we exceed the 80 columns sometimes.

That's why, for consistency, I always shortcut to *uc_map a reference
to a clamp group and use that variable name consistently in the code.

I'll see if it's possible to get rid of the shortcut in the next version.

--
#include <best/regards.h>

Patrick Bellasi