Messages in this thread | | | Date | Tue, 31 Oct 2023 16:52:23 +0100 | Subject | Re: [RFC PATCH 1/6] sched/uclamp: Track uclamped util_avg in sched_avg | From | Dietmar Eggemann <> |
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On 04/10/2023 11:04, Hongyan Xia wrote: > From: Hongyan Xia <hongyan.xia2@arm.com>
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> @@ -6445,6 +6450,21 @@ static int sched_idle_cpu(int cpu) > } > #endif > > +void ___update_util_avg_uclamp(struct sched_avg *avg, struct sched_entity *se);
IMHO, `struct sched_avg *avg` can only be the one of a cfs_rq. So passing a cfs_rq would eliminate the question whether this can be from another se.
> +static void update_se_chain(struct task_struct *p) > +{ > +#ifdef CONFIG_UCLAMP_TASK > + struct sched_entity *se = &p->se; > + struct rq *rq = task_rq(p); > + > + for_each_sched_entity(se) { > + struct cfs_rq *cfs_rq = cfs_rq_of(se); > + > + ___update_util_avg_uclamp(&cfs_rq->avg, se); > + } > +#endif > +} > /* > * The enqueue_task method is called before nr_running is > * increased. Here we update the fair scheduling stats and > @@ -6511,6 +6531,16 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) > goto enqueue_throttle; > } > > + /* > + * Re-evaluate the se hierarchy now that on_rq is true. This is > + * important to enforce uclamp the moment a task with uclamp is > + * enqueued, rather than waiting a timer tick for uclamp to kick in. > + * > + * XXX: This duplicates some of the work already done in the above for > + * loops. > + */ > + update_se_chain(p);
I try to figure out why this is necessary here:
enqueue_task_fair() for_each_sched_entity() enqueue_entity() update_load_avg() __update_load_avg_se() ___update_util_avg_uclamp() <-- if se->on_rq, update p (se) if we cross PELT period (1) boundaries ___decay_util_avg_uclamp_towards() <-- decay p (se) (2)
enqueue_util_avg_uclamp() <-- enqueue p into cfs_rq (3)
se->on_rq = 1 <-- set p (se) on_rq (4)
for_each_sched_entity() update_load_avg() <-- update all on_rq se's in the hierarchy (5)
update_se_chain() <-- update p (se) and its se hierarchy (6)
(1) Skip p since it is !se->on_rq.
(2) Decay p->se->avg.util_avg_uclamp to 0 since it was sleeping.
(3) Attach p to its cfs_rq
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(6) Update all all se's and cfs_rq's involved in p's task_group hierarchy (including propagation from se (level=x+1) to cfs_rq (level=x))
Question for me is why can't you integrate the util_avg_uclamp signals for se's and cfs_rq's/rq's much closer into existing PELT functions?
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