Messages in this thread | | | Date | Tue, 24 May 2022 17:35:11 +0800 | Subject | Re: [External] Re: [PATCH] sched/fair: optimize and simplify rq leaf_cfs_rq_list | From | Chengming Zhou <> |
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On 2022/5/24 00:23, Vincent Guittot wrote: > On Wed, 27 Apr 2022 at 18:07, Chengming Zhou > <zhouchengming@bytedance.com> wrote: [...] >> kernel/sched/fair.c | 72 ++++++++++----------------------------------- >> 1 file changed, 16 insertions(+), 56 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 1ad18b5cc1b8..083c3d32c899 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -309,6 +309,8 @@ const struct sched_class fair_sched_class; >> >> #ifdef CONFIG_FAIR_GROUP_SCHED >> >> +static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); >> + >> /* Walk up scheduling entities hierarchy */ >> #define for_each_sched_entity(se) \ >> for (; se; se = se->parent) >> @@ -331,7 +333,7 @@ static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) >> struct rq *rq = rq_of(cfs_rq); >> int cpu = cpu_of(rq); >> >> - if (cfs_rq->on_list) >> + if (cfs_rq->on_list || throttled_hierarchy(cfs_rq)) > > Please move throttled_hierarchy() outside list_add_leaf_cfs_rq() > because the task will not be added in this case which is quite > misleading
Ok, will do. I will move throttled_hierarchy() outside.
> > I will continue to check the various corner cases but I haven't seen > problem so far with your method
Thanks!
> >> return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list; >> >> cfs_rq->on_list = 1; >> @@ -3242,8 +3244,6 @@ static long calc_group_shares(struct cfs_rq *cfs_rq) >> } >> #endif /* CONFIG_SMP */ >> >> -static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); >> - >> /* >> * Recomputes the group entity based on the current state of its group >> * runqueue. >> @@ -4356,16 +4356,10 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) >> __enqueue_entity(cfs_rq, se); >> se->on_rq = 1; >> >> - /* >> - * When bandwidth control is enabled, cfs might have been removed >> - * because of a parent been throttled but cfs->nr_running > 1. Try to >> - * add it unconditionally. >> - */ >> - if (cfs_rq->nr_running == 1 || cfs_bandwidth_used()) >> + if (cfs_rq->nr_running == 1) { >> list_add_leaf_cfs_rq(cfs_rq); >> - >> - if (cfs_rq->nr_running == 1) >> check_enqueue_throttle(cfs_rq); >> + } >> } >> >> static void __clear_buddies_last(struct sched_entity *se) >> @@ -4980,11 +4974,18 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) >> /* update hierarchical throttle state */ >> walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); >> >> - /* Nothing to run but something to decay (on_list)? Complete the branch */ >> if (!cfs_rq->load.weight) { >> - if (cfs_rq->on_list) >> - goto unthrottle_throttle; >> - return; >> + if (!cfs_rq->on_list) >> + return; >> + /* >> + * Nothing to run but something to decay (on_list)? >> + * Complete the branch. >> + */ >> + for_each_sched_entity(se) { >> + if (list_add_leaf_cfs_rq(cfs_rq_of(se))) >> + break; >> + } >> + goto unthrottle_throttle; >> } >> >> task_delta = cfs_rq->h_nr_running; >> @@ -5022,31 +5023,12 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) >> /* end evaluation on encountering a throttled cfs_rq */ >> if (cfs_rq_throttled(qcfs_rq)) >> goto unthrottle_throttle; >> - >> - /* >> - * One parent has been throttled and cfs_rq removed from the >> - * list. Add it back to not break the leaf list. >> - */ >> - if (throttled_hierarchy(qcfs_rq)) >> - list_add_leaf_cfs_rq(qcfs_rq); >> } >> >> /* At this point se is NULL and we are at root level*/ >> add_nr_running(rq, task_delta); >> >> unthrottle_throttle: >> - /* >> - * The cfs_rq_throttled() breaks in the above iteration can result in >> - * incomplete leaf list maintenance, resulting in triggering the >> - * assertion below. >> - */ >> - for_each_sched_entity(se) { >> - struct cfs_rq *qcfs_rq = cfs_rq_of(se); >> - >> - if (list_add_leaf_cfs_rq(qcfs_rq)) >> - break; >> - } >> - >> assert_list_leaf_cfs_rq(rq); >> >> /* Determine whether we need to wake up potentially idle CPU: */ >> @@ -5701,13 +5683,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) >> /* end evaluation on encountering a throttled cfs_rq */ >> if (cfs_rq_throttled(cfs_rq)) >> goto enqueue_throttle; >> - >> - /* >> - * One parent has been throttled and cfs_rq removed from the >> - * list. Add it back to not break the leaf list. >> - */ >> - if (throttled_hierarchy(cfs_rq)) >> - list_add_leaf_cfs_rq(cfs_rq); >> } >> >> /* At this point se is NULL and we are at root level*/ >> @@ -5731,21 +5706,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) >> update_overutilized_status(rq); >> >> enqueue_throttle: >> - if (cfs_bandwidth_used()) { >> - /* >> - * When bandwidth control is enabled; the cfs_rq_throttled() >> - * breaks in the above iteration can result in incomplete >> - * leaf list maintenance, resulting in triggering the assertion >> - * below. >> - */ >> - for_each_sched_entity(se) { >> - cfs_rq = cfs_rq_of(se); >> - >> - if (list_add_leaf_cfs_rq(cfs_rq)) >> - break; >> - } >> - } >> - >> assert_list_leaf_cfs_rq(rq); >> >> hrtick_update(rq); >> -- >> 2.35.2 >>
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