Messages in this thread | | | Subject | Re: [PATCH 5/8] sched,cfs: use explicit cfs_rq of parent se helper | From | Dietmar Eggemann <> | Date | Mon, 24 Jun 2019 13:24:10 +0200 |
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On 6/20/19 6:29 PM, Rik van Riel wrote: > On Thu, 2019-06-20 at 18:23 +0200, Dietmar Eggemann wrote: >> On 6/12/19 9:32 PM, Rik van Riel wrote:
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>>> @@ -7779,7 +7788,7 @@ static void update_cfs_rq_h_load(struct >>> cfs_rq *cfs_rq) >>> >>> WRITE_ONCE(cfs_rq->h_load_next, NULL); >>> for_each_sched_entity(se) { >>> - cfs_rq = cfs_rq_of(se); >>> + cfs_rq = group_cfs_rq_of_parent(se); >> >> Why do you change this here? task_se_h_load() calls >> update_cfs_rq_h_load() with cfs_rq = group_cfs_rq_of_parent(se) >> because >> the task might not be on the cfs_rq yet. > > Because patch 6 points cfs_rq_of(se) at the CPU's top level > cfs_rq for every task se ... > > ... but I guess since I have not changed where the cfs_rq_of > points for cgroup sched_entities, this change is not necessary > at this time, and I should be able to go without it, in this > function.
IMHO, since you only change set_task_rq() (p->se.cfs_rq = &cpu_rq(cpu)->cfs instead of tg->cfs_rq[cpu] in 8/8) (used for a task) and not init_tg_cfs_entry() (used for a taskgroup), 'cfs_rq_of(se) == se->parent->my_q' should still be true in update_cfs_rq_h_load().
update_cfs_rq_h_load() only deals with se's representing taskgroups. So cfs_rq_of(se) and group_cfs_rq_of_parent(se) should deliver the same result for these se's.
>> But inside update_cfs_rq_h_load() the first se is derived from >> cfs_rq->tg->se[cpu_of(rq)] so in the first for_each_sched_entity() >> loop >> we should still start with group_cfs_rq() (se->my_q) ?
Here I was wrong. The first loop did use cfs_rq_of() and not group_cfs_rq(). [...]
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