Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 30 Jan 2014 13:18:09 +0100 | Subject | Re: [PATCH 7/9] sched/fair: Optimize cgroup pick_next_task_fair |
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On 28 January 2014 18:16, Peter Zijlstra <peterz@infradead.org> wrote:
[snip]
> > @@ -4662,9 +4682,86 @@ static void check_preempt_wakeup(struct > static struct task_struct * > pick_next_task_fair(struct rq *rq, struct task_struct *prev) > { > - struct task_struct *p; > struct cfs_rq *cfs_rq = &rq->cfs; > struct sched_entity *se; > + struct task_struct *p; > + > +#ifdef CONFIG_FAIR_GROUP_SCHED > + if (!cfs_rq->nr_running) > + return NULL;
Couldn't you move the test above out of the CONFIG_FAIR_GROUP_SCHED and remove the same test that is done after the simple label
Vincent
> + > + if (prev->sched_class != &fair_sched_class) > + goto simple; > + > + /* > + * Because of the set_next_buddy() in dequeue_task_fair() it is rather > + * likely that a next task is from the same cgroup as the current. > + * > + * Therefore attempt to avoid putting and setting the entire cgroup > + * hierarchy, only change the part that actually changes. > + */ > + > + do { > + struct sched_entity *curr = cfs_rq->curr; > + > + /* > + * Since we got here without doing put_prev_entity() we also > + * have to consider cfs_rq->curr. If it is still a runnable > + * entity, update_curr() will update its vruntime, otherwise > + * forget we've ever seen it. > + */ > + if (curr && curr->on_rq) > + update_curr(cfs_rq); > + else > + curr = NULL; > + > + /* > + * This call to check_cfs_rq_runtime() will do the throttle and > + * dequeue its entity in the parent(s). Therefore the 'simple' > + * nr_running test will indeed be correct. > + */ > + if (unlikely(check_cfs_rq_runtime(cfs_rq))) > + goto simple; > + > + se = pick_next_entity(cfs_rq, curr); > + cfs_rq = group_cfs_rq(se); > + } while (cfs_rq); > + > + p = task_of(se); > + > + /* > + * Since we haven't yet done put_prev_entity and if the selected task > + * is a different task than we started out with, try and touch the > + * least amount of cfs_rqs. > + */ > + if (prev != p) { > + struct sched_entity *pse = &prev->se; > + > + while (!(cfs_rq = is_same_group(se, pse))) { > + int se_depth = se->depth; > + int pse_depth = pse->depth; > + > + if (se_depth <= pse_depth) { > + put_prev_entity(cfs_rq_of(pse), pse); > + pse = parent_entity(pse); > + } > + if (se_depth >= pse_depth) { > + set_next_entity(cfs_rq_of(se), se); > + se = parent_entity(se); > + } > + } > + > + put_prev_entity(cfs_rq, pse); > + set_next_entity(cfs_rq, se); > + } > + > + if (hrtick_enabled(rq)) > + hrtick_start_fair(rq, p); > + > + return p; > +simple: > + cfs_rq = &rq->cfs; > +#endif > > if (!cfs_rq->nr_running) > return NULL; > @@ -4672,12 +4769,13 @@ pick_next_task_fair(struct rq *rq, struc > prev->sched_class->put_prev_task(rq, prev); > > do { > - se = pick_next_entity(cfs_rq); > + se = pick_next_entity(cfs_rq, NULL); > set_next_entity(cfs_rq, se); > cfs_rq = group_cfs_rq(se); > } while (cfs_rq); > > p = task_of(se); > + > if (hrtick_enabled(rq)) > hrtick_start_fair(rq, p); > > >
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