Messages in this thread | | | Date | Thu, 21 Nov 2013 17:16:50 +0100 | From | Juri Lelli <> | Subject | Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic. |
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On 11/21/2013 05:08 PM, Paul E. McKenney wrote: > On Thu, Nov 21, 2013 at 03:13:28PM +0100, Juri Lelli wrote: >> On 11/20/2013 07:51 PM, Steven Rostedt wrote: >>> On Thu, 7 Nov 2013 14:43:38 +0100 >>> Juri Lelli <juri.lelli@gmail.com> wrote: >>> >>> >>>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >>>> index cb93f2e..18a73b4 100644 >>>> --- a/kernel/sched/deadline.c >>>> +++ b/kernel/sched/deadline.c >>>> @@ -10,6 +10,7 @@ >>>> * miss some of their deadlines), and won't affect any other task. >>>> * >>>> * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>, >>>> + * Juri Lelli <juri.lelli@gmail.com>, >>>> * Michael Trimarchi <michael@amarulasolutions.com>, >>>> * Fabio Checconi <fchecconi@gmail.com> >>>> */ >>>> @@ -20,6 +21,15 @@ static inline int dl_time_before(u64 a, u64 b) >>>> return (s64)(a - b) < 0; >>>> } >>>> >>>> +/* >>>> + * Tells if entity @a should preempt entity @b. >>>> + */ >>>> +static inline >>>> +int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b) >>>> +{ >>>> + return dl_time_before(a->deadline, b->deadline); >>>> +} >>>> + >>>> static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se) >>>> { >>>> return container_of(dl_se, struct task_struct, dl); >>>> @@ -53,8 +63,168 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq) >>>> void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq) >>>> { >>>> dl_rq->rb_root = RB_ROOT; >>>> + >>>> +#ifdef CONFIG_SMP >>>> + /* zero means no -deadline tasks */ >>> >>> I'm curious to why you add the '-' to -deadline. >>> >> >> I guess "deadline tasks" is too much generic; "SCHED_DEADLINE tasks" too long; >> "DL" or "-dl" can be associated to "download". Nothing special in the end, just >> tought it was a reasonable abbreviation. > > My guess was that "-deadline" was an abbreviation for tasks that had > missed their deadline, just so you know. ;-) >
Argh! ;)
Actually, thinking about it twice: if we call "-rt tasks" things that are governed by code that resides in sched/rt.c, we could agree on "-deadline tasks" for things that pass through sched/deadline.c.
Thanks,
- Juri
>>>> + dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0; >>>> + >>>> + dl_rq->dl_nr_migratory = 0; >>>> + dl_rq->overloaded = 0; >>>> + dl_rq->pushable_dl_tasks_root = RB_ROOT; >>>> +#endif >>>> +} >>>> + >>>> +#ifdef CONFIG_SMP >>>> + >>>> +static inline int dl_overloaded(struct rq *rq) >>>> +{ >>>> + return atomic_read(&rq->rd->dlo_count); >>>> +} >>>> + >>>> +static inline void dl_set_overload(struct rq *rq) >>>> +{ >>>> + if (!rq->online) >>>> + return; >>>> + >>>> + cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask); >>>> + /* >>>> + * Must be visible before the overload count is >>>> + * set (as in sched_rt.c). >>>> + * >>>> + * Matched by the barrier in pull_dl_task(). >>>> + */ >>>> + smp_wmb(); >>>> + atomic_inc(&rq->rd->dlo_count); >>>> +} >>>> + >>>> +static inline void dl_clear_overload(struct rq *rq) >>>> +{ >>>> + if (!rq->online) >>>> + return; >>>> + >>>> + atomic_dec(&rq->rd->dlo_count); >>>> + cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask); >>>> +} >>>> + >>>> +static void update_dl_migration(struct dl_rq *dl_rq) >>>> +{ >>>> + if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_total > 1) { >>>> + if (!dl_rq->overloaded) { >>>> + dl_set_overload(rq_of_dl_rq(dl_rq)); >>>> + dl_rq->overloaded = 1; >>>> + } >>>> + } else if (dl_rq->overloaded) { >>>> + dl_clear_overload(rq_of_dl_rq(dl_rq)); >>>> + dl_rq->overloaded = 0; >>>> + } >>>> +} >>>> + >>>> +static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> + struct task_struct *p = dl_task_of(dl_se); >>>> + dl_rq = &rq_of_dl_rq(dl_rq)->dl; >>>> + >>>> + dl_rq->dl_nr_total++; >>>> + if (p->nr_cpus_allowed > 1) >>>> + dl_rq->dl_nr_migratory++; >>>> + >>>> + update_dl_migration(dl_rq); >>>> +} >>>> + >>>> +static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> + struct task_struct *p = dl_task_of(dl_se); >>>> + dl_rq = &rq_of_dl_rq(dl_rq)->dl; >>>> + >>>> + dl_rq->dl_nr_total--; >>>> + if (p->nr_cpus_allowed > 1) >>>> + dl_rq->dl_nr_migratory--; >>>> + >>>> + update_dl_migration(dl_rq); >>>> +} >>>> + >>>> +/* >>>> + * The list of pushable -deadline task is not a plist, like in >>>> + * sched_rt.c, it is an rb-tree with tasks ordered by deadline. >>>> + */ >>>> +static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p) >>>> +{ >>>> + struct dl_rq *dl_rq = &rq->dl; >>>> + struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node; >>>> + struct rb_node *parent = NULL; >>>> + struct task_struct *entry; >>>> + int leftmost = 1; >>>> + >>>> + BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks)); >>>> + >>>> + while (*link) { >>>> + parent = *link; >>>> + entry = rb_entry(parent, struct task_struct, >>>> + pushable_dl_tasks); >>>> + if (dl_entity_preempt(&p->dl, &entry->dl)) >>>> + link = &parent->rb_left; >>>> + else { >>>> + link = &parent->rb_right; >>>> + leftmost = 0; >>>> + } >>>> + } >>>> + >>>> + if (leftmost) >>>> + dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks; >>>> + >>>> + rb_link_node(&p->pushable_dl_tasks, parent, link); >>>> + rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root); >>>> +} >>>> + >>>> +static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p) >>>> +{ >>>> + struct dl_rq *dl_rq = &rq->dl; >>>> + >>>> + if (RB_EMPTY_NODE(&p->pushable_dl_tasks)) >>>> + return; >>>> + >>>> + if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) { >>>> + struct rb_node *next_node; >>>> + >>>> + next_node = rb_next(&p->pushable_dl_tasks); >>>> + dl_rq->pushable_dl_tasks_leftmost = next_node; >>>> + } >>>> + >>>> + rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root); >>>> + RB_CLEAR_NODE(&p->pushable_dl_tasks); >>>> +} >>>> + >>>> +static inline int has_pushable_dl_tasks(struct rq *rq) >>>> +{ >>>> + return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root); >>>> +} >>>> + >>>> +static int push_dl_task(struct rq *rq); >>>> + >>>> +#else >>>> + >>>> +static inline >>>> +void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p) >>>> +{ >>>> +} >>>> + >>>> +static inline >>>> +void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p) >>>> +{ >>>> +} >>>> + >>>> +static inline >>>> +void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> +} >>>> + >>>> +static inline >>>> +void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> } >>>> >>>> +#endif /* CONFIG_SMP */ >>>> + >>>> static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags); >>>> static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags); >>>> static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, >>>> @@ -307,6 +477,14 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) >>>> check_preempt_curr_dl(rq, p, 0); >>>> else >>>> resched_task(rq->curr); >>>> +#ifdef CONFIG_SMP >>>> + /* >>>> + * Queueing this task back might have overloaded rq, >>>> + * check if we need to kick someone away. >>>> + */ >>>> + if (has_pushable_dl_tasks(rq)) >>>> + push_dl_task(rq); >>>> +#endif >>>> } >>>> unlock: >>>> raw_spin_unlock(&rq->lock); >>>> @@ -397,6 +575,100 @@ static void update_curr_dl(struct rq *rq) >>>> } >>>> } >>>> >>>> +#ifdef CONFIG_SMP >>>> + >>>> +static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu); >>>> + >>>> +static inline u64 next_deadline(struct rq *rq) >>>> +{ >>>> + struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu); >>>> + >>>> + if (next && dl_prio(next->prio)) >>>> + return next->dl.deadline; >>>> + else >>>> + return 0; >>>> +} >>>> + >>>> +static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) >>>> +{ >>>> + struct rq *rq = rq_of_dl_rq(dl_rq); >>>> + >>>> + if (dl_rq->earliest_dl.curr == 0 || >>>> + dl_time_before(deadline, dl_rq->earliest_dl.curr)) { >>>> + /* >>>> + * If the dl_rq had no -deadline tasks, or if the new task >>>> + * has shorter deadline than the current one on dl_rq, we >>>> + * know that the previous earliest becomes our next earliest, >>>> + * as the new task becomes the earliest itself. >>>> + */ >>>> + dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr; >>>> + dl_rq->earliest_dl.curr = deadline; >>>> + } else if (dl_rq->earliest_dl.next == 0 || >>>> + dl_time_before(deadline, dl_rq->earliest_dl.next)) { >>>> + /* >>>> + * On the other hand, if the new -deadline task has a >>>> + * a later deadline than the earliest one on dl_rq, but >>>> + * it is earlier than the next (if any), we must >>>> + * recompute the next-earliest. >>>> + */ >>>> + dl_rq->earliest_dl.next = next_deadline(rq); >>>> + } >>>> +} >>>> + >>>> +static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) >>>> +{ >>>> + struct rq *rq = rq_of_dl_rq(dl_rq); >>>> + >>>> + /* >>>> + * Since we may have removed our earliest (and/or next earliest) >>>> + * task we must recompute them. >>>> + */ >>>> + if (!dl_rq->dl_nr_running) { >>>> + dl_rq->earliest_dl.curr = 0; >>>> + dl_rq->earliest_dl.next = 0; >>>> + } else { >>>> + struct rb_node *leftmost = dl_rq->rb_leftmost; >>>> + struct sched_dl_entity *entry; >>>> + >>>> + entry = rb_entry(leftmost, struct sched_dl_entity, rb_node); >>>> + dl_rq->earliest_dl.curr = entry->deadline; >>>> + dl_rq->earliest_dl.next = next_deadline(rq); >>>> + } >>>> +} >>>> + >>>> +#else >>>> + >>>> +static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {} >>>> +static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {} >>>> + >>>> +#endif /* CONFIG_SMP */ >>>> + >>>> +static inline >>>> +void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> + int prio = dl_task_of(dl_se)->prio; >>>> + u64 deadline = dl_se->deadline; >>>> + >>>> + WARN_ON(!dl_prio(prio)); >>>> + dl_rq->dl_nr_running++; >>>> + >>>> + inc_dl_deadline(dl_rq, deadline); >>>> + inc_dl_migration(dl_se, dl_rq); >>>> +} >>>> + >>>> +static inline >>>> +void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) >>>> +{ >>>> + int prio = dl_task_of(dl_se)->prio; >>>> + >>>> + WARN_ON(!dl_prio(prio)); >>>> + WARN_ON(!dl_rq->dl_nr_running); >>>> + dl_rq->dl_nr_running--; >>>> + >>>> + dec_dl_deadline(dl_rq, dl_se->deadline); >>>> + dec_dl_migration(dl_se, dl_rq); >>>> +} >>>> + >>>> static void __enqueue_dl_entity(struct sched_dl_entity *dl_se) >>>> { >>>> struct dl_rq *dl_rq = dl_rq_of_se(dl_se); >>>> @@ -424,7 +696,7 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se) >>>> rb_link_node(&dl_se->rb_node, parent, link); >>>> rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root); >>>> >>>> - dl_rq->dl_nr_running++; >>>> + inc_dl_tasks(dl_se, dl_rq); >>>> } >>>> >>>> static void __dequeue_dl_entity(struct sched_dl_entity *dl_se) >>>> @@ -444,7 +716,7 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se) >>>> rb_erase(&dl_se->rb_node, &dl_rq->rb_root); >>>> RB_CLEAR_NODE(&dl_se->rb_node); >>>> >>>> - dl_rq->dl_nr_running--; >>>> + dec_dl_tasks(dl_se, dl_rq); >>>> } >>>> >>>> static void >>>> @@ -482,12 +754,17 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) >>>> return; >>>> >>>> enqueue_dl_entity(&p->dl, flags); >>>> + >>>> + if (!task_current(rq, p) && p->nr_cpus_allowed > 1) >>>> + enqueue_pushable_dl_task(rq, p); >>>> + >>>> inc_nr_running(rq); >>>> } >>>> >>>> static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) >>>> { >>>> dequeue_dl_entity(&p->dl); >>>> + dequeue_pushable_dl_task(rq, p); >>>> } >>>> >>>> static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) >>>> @@ -525,6 +802,77 @@ static void yield_task_dl(struct rq *rq) >>>> update_curr_dl(rq); >>>> } >>>> >>>> +#ifdef CONFIG_SMP >>>> + >>>> +static int find_later_rq(struct task_struct *task); >>>> +static int latest_cpu_find(struct cpumask *span, >>>> + struct task_struct *task, >>>> + struct cpumask *later_mask); >>>> + >>>> +static int >>>> +select_task_rq_dl(struct task_struct *p, int sd_flag, int flags) >>>> +{ >>>> + struct task_struct *curr; >>>> + struct rq *rq; >>>> + int cpu; >>>> + >>>> + cpu = task_cpu(p); >>>> + >>>> + if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK) >>>> + goto out; >>>> + >>>> + rq = cpu_rq(cpu); >>>> + >>>> + rcu_read_lock(); >>>> + curr = ACCESS_ONCE(rq->curr); /* unlocked access */ >>>> + >>>> + /* >>>> + * If we are dealing with a -deadline task, we must >>>> + * decide where to wake it up. >>>> + * If it has a later deadline and the current task >>>> + * on this rq can't move (provided the waking task >>>> + * can!) we prefer to send it somewhere else. On the >>>> + * other hand, if it has a shorter deadline, we >>>> + * try to make it stay here, it might be important. >>>> + */ >>>> + if (unlikely(dl_task(curr)) && >>>> + (curr->nr_cpus_allowed < 2 || >>>> + !dl_entity_preempt(&p->dl, &curr->dl)) && >>>> + (p->nr_cpus_allowed > 1)) { >>>> + int target = find_later_rq(p); >>>> + >>>> + if (target != -1) >>>> + cpu = target; >>>> + } >>>> + rcu_read_unlock(); >>>> + >>>> +out: >>>> + return cpu; >>>> +} >>>> + >>>> +static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) >>>> +{ >>>> + /* >>>> + * Current can't be migrated, useless to reschedule, >>>> + * let's hope p can move out. >>>> + */ >>>> + if (rq->curr->nr_cpus_allowed == 1 || >>>> + latest_cpu_find(rq->rd->span, rq->curr, NULL) == -1) >>>> + return; >>>> + >>>> + /* >>>> + * p is migratable, so let's not schedule it and >>>> + * see if it is pushed or pulled somewhere else. >>>> + */ >>>> + if (p->nr_cpus_allowed != 1 && >>>> + latest_cpu_find(rq->rd->span, p, NULL) != -1) >>>> + return; >>>> + >>>> + resched_task(rq->curr); >>>> +} >>>> + >>>> +#endif /* CONFIG_SMP */ >>>> + >>>> /* >>>> * Only called when both the current and waking task are -deadline >>>> * tasks. >>>> @@ -532,8 +880,20 @@ static void yield_task_dl(struct rq *rq) >>>> static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, >>>> int flags) >>>> { >>>> - if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline)) >>>> + if (dl_entity_preempt(&p->dl, &rq->curr->dl)) { >>>> resched_task(rq->curr); >>>> + return; >>>> + } >>>> + >>>> +#ifdef CONFIG_SMP >>>> + /* >>>> + * In the unlikely case current and p have the same deadline >>>> + * let us try to decide what's the best thing to do... >>>> + */ >>>> + if ((s64)(p->dl.deadline - rq->curr->dl.deadline) == 0 && >>>> + !need_resched()) >>>> + check_preempt_equal_dl(rq, p); >>>> +#endif /* CONFIG_SMP */ >>>> } >>>> >>>> #ifdef CONFIG_SCHED_HRTICK >>>> @@ -573,16 +933,29 @@ struct task_struct *pick_next_task_dl(struct rq *rq) >>>> >>>> p = dl_task_of(dl_se); >>>> p->se.exec_start = rq_clock_task(rq); >>>> + >>>> + /* Running task will never be pushed. */ >>>> + if (p) >>>> + dequeue_pushable_dl_task(rq, p); >>>> + >>>> #ifdef CONFIG_SCHED_HRTICK >>>> if (hrtick_enabled(rq)) >>>> start_hrtick_dl(rq, p); >>>> #endif >>>> + >>>> +#ifdef CONFIG_SMP >>>> + rq->post_schedule = has_pushable_dl_tasks(rq); >>>> +#endif /* CONFIG_SMP */ >>>> + >>>> return p; >>>> } >>>> >>>> static void put_prev_task_dl(struct rq *rq, struct task_struct *p) >>>> { >>>> update_curr_dl(rq); >>>> + >>>> + if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1) >>>> + enqueue_pushable_dl_task(rq, p); >>>> } >>>> >>>> static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued) >>>> @@ -616,16 +989,517 @@ static void set_curr_task_dl(struct rq *rq) >>>> struct task_struct *p = rq->curr; >>>> >>>> p->se.exec_start = rq_clock_task(rq); >>>> + >>>> + /* You can't push away the running task */ >>>> + dequeue_pushable_dl_task(rq, p); >>>> +} >>>> + >>>> +#ifdef CONFIG_SMP >>>> + >>>> +/* Only try algorithms three times */ >>>> +#define DL_MAX_TRIES 3 >>>> + >>>> +static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu) >>>> +{ >>>> + if (!task_running(rq, p) && >>>> + (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) && >>>> + (p->nr_cpus_allowed > 1)) >>>> + return 1; >>>> + >>>> + return 0; >>>> +} >>>> + >>>> +/* Returns the second earliest -deadline task, NULL otherwise */ >>>> +static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu) >>>> +{ >>>> + struct rb_node *next_node = rq->dl.rb_leftmost; >>>> + struct sched_dl_entity *dl_se; >>>> + struct task_struct *p = NULL; >>>> + >>>> +next_node: >>>> + next_node = rb_next(next_node); >>>> + if (next_node) { >>>> + dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node); >>>> + p = dl_task_of(dl_se); >>>> + >>>> + if (pick_dl_task(rq, p, cpu)) >>>> + return p; >>>> + >>>> + goto next_node; >>>> + } >>>> + >>>> + return NULL; >>>> +} >>>> + >>>> +static int latest_cpu_find(struct cpumask *span, >>>> + struct task_struct *task, >>>> + struct cpumask *later_mask) >>>> +{ >>>> + const struct sched_dl_entity *dl_se = &task->dl; >>>> + int cpu, found = -1, best = 0; >>>> + u64 max_dl = 0; >>>> + >>>> + for_each_cpu(cpu, span) { >>>> + struct rq *rq = cpu_rq(cpu); >>>> + struct dl_rq *dl_rq = &rq->dl; >>>> + >>>> + if (cpumask_test_cpu(cpu, &task->cpus_allowed) && >>>> + (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline, >>>> + dl_rq->earliest_dl.curr))) { >>>> + if (later_mask) >>>> + cpumask_set_cpu(cpu, later_mask); >>>> + if (!best && !dl_rq->dl_nr_running) { >>>> + best = 1; >>>> + found = cpu; >>>> + } else if (!best && >>>> + dl_time_before(max_dl, >>>> + dl_rq->earliest_dl.curr)) { >>> >>> Ug, the above is hard to read. What about: >>> >>> if (!best) { >>> if (!dl_rq->dl_nr_running) { >>> best = 1; >>> found = cpu; >>> } elsif (dl_time_before(...)) { >>> ... >>> } >>> } >>> >> >> This is completely removed in 13/14. I don't like it either, but since we end >> up removing this mess, do you think we still have to fix this here? >> >>> Also, I would think dl should be nice to rt as well. There may be a >>> idle CPU or a non rt task, and this could pick a CPU running an RT >>> task. Worse yet, that RT task may be pinned to that CPU. >>> >> >> Well, in 13/14 we introduce a free_cpus mask. A CPU is considered free if it >> doesn't have any -deadline task running. We can modify that excluding also CPUs >> running RT tasks, but I have to think a bit if we can do this also from -rt code. >> >>> We should be able to incorporate cpuprio_find() to be dl aware too. >>> That is, work for both -rt and -dl. >>> >> >> Like checking if a -dl task is running on the cpu chosen for pushing an -rt >> task, and continue searching in that case. >> >>> >>> >>>> + max_dl = dl_rq->earliest_dl.curr; >>>> + found = cpu; >>>> + } >>>> + } else if (later_mask) >>>> + cpumask_clear_cpu(cpu, later_mask); >>>> + } >>>> + >>>> + return found; >>>> +} >>>> + >>>> +static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl); >>>> + >>>> +static int find_later_rq(struct task_struct *task) >>>> +{ >>>> + struct sched_domain *sd; >>>> + struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl); >>>> + int this_cpu = smp_processor_id(); >>>> + int best_cpu, cpu = task_cpu(task); >>>> + >>>> + /* Make sure the mask is initialized first */ >>>> + if (unlikely(!later_mask)) >>>> + return -1; >>>> + >>>> + if (task->nr_cpus_allowed == 1) >>>> + return -1; >>>> + >>>> + best_cpu = latest_cpu_find(task_rq(task)->rd->span, task, later_mask); >>>> + if (best_cpu == -1) >>>> + return -1; >>>> + >>>> + /* >>>> + * If we are here, some target has been found, >>>> + * the most suitable of which is cached in best_cpu. >>>> + * This is, among the runqueues where the current tasks >>>> + * have later deadlines than the task's one, the rq >>>> + * with the latest possible one. >>>> + * >>>> + * Now we check how well this matches with task's >>>> + * affinity and system topology. >>>> + * >>>> + * The last cpu where the task run is our first >>>> + * guess, since it is most likely cache-hot there. >>>> + */ >>>> + if (cpumask_test_cpu(cpu, later_mask)) >>>> + return cpu; >>>> + /* >>>> + * Check if this_cpu is to be skipped (i.e., it is >>>> + * not in the mask) or not. >>>> + */ >>>> + if (!cpumask_test_cpu(this_cpu, later_mask)) >>>> + this_cpu = -1; >>>> + >>>> + rcu_read_lock(); >>>> + for_each_domain(cpu, sd) { >>>> + if (sd->flags & SD_WAKE_AFFINE) { >>>> + >>>> + /* >>>> + * If possible, preempting this_cpu is >>>> + * cheaper than migrating. >>>> + */ >>>> + if (this_cpu != -1 && >>>> + cpumask_test_cpu(this_cpu, sched_domain_span(sd))) { >>>> + rcu_read_unlock(); >>>> + return this_cpu; >>>> + } >>>> + >>>> + /* >>>> + * Last chance: if best_cpu is valid and is >>>> + * in the mask, that becomes our choice. >>>> + */ >>>> + if (best_cpu < nr_cpu_ids && >>>> + cpumask_test_cpu(best_cpu, sched_domain_span(sd))) { >>>> + rcu_read_unlock(); >>>> + return best_cpu; >>>> + } >>>> + } >>>> + } >>>> + rcu_read_unlock(); >>>> + >>>> + /* >>>> + * At this point, all our guesses failed, we just return >>>> + * 'something', and let the caller sort the things out. >>>> + */ >>>> + if (this_cpu != -1) >>>> + return this_cpu; >>>> + >>>> + cpu = cpumask_any(later_mask); >>>> + if (cpu < nr_cpu_ids) >>>> + return cpu; >>>> + >>>> + return -1; >>>> +} >>>> + >>>> +/* Locks the rq it finds */ >>>> +static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq) >>>> +{ >>>> + struct rq *later_rq = NULL; >>>> + int tries; >>>> + int cpu; >>>> + >>>> + for (tries = 0; tries < DL_MAX_TRIES; tries++) { >>>> + cpu = find_later_rq(task); >>>> + >>>> + if ((cpu == -1) || (cpu == rq->cpu)) >>>> + break; >>>> + >>>> + later_rq = cpu_rq(cpu); >>>> + >>>> + /* Retry if something changed. */ >>>> + if (double_lock_balance(rq, later_rq)) { >>>> + if (unlikely(task_rq(task) != rq || >>>> + !cpumask_test_cpu(later_rq->cpu, >>>> + &task->cpus_allowed) || >>>> + task_running(rq, task) || !task->on_rq)) { >>>> + double_unlock_balance(rq, later_rq); >>>> + later_rq = NULL; >>>> + break; >>>> + } >>>> + } >>>> + >>>> + /* >>>> + * If the rq we found has no -deadline task, or >>>> + * its earliest one has a later deadline than our >>>> + * task, the rq is a good one. >>>> + */ >>>> + if (!later_rq->dl.dl_nr_running || >>>> + dl_time_before(task->dl.deadline, >>>> + later_rq->dl.earliest_dl.curr)) >>>> + break; >>>> + >>>> + /* Otherwise we try again. */ >>>> + double_unlock_balance(rq, later_rq); >>>> + later_rq = NULL; >>>> + } >>>> + >>>> + return later_rq; >>>> } >>>> >>>> +static struct task_struct *pick_next_pushable_dl_task(struct rq *rq) >>>> +{ >>>> + struct task_struct *p; >>>> + >>>> + if (!has_pushable_dl_tasks(rq)) >>>> + return NULL; >>>> + >>>> + p = rb_entry(rq->dl.pushable_dl_tasks_leftmost, >>>> + struct task_struct, pushable_dl_tasks); >>>> + >>>> + BUG_ON(rq->cpu != task_cpu(p)); >>>> + BUG_ON(task_current(rq, p)); >>>> + BUG_ON(p->nr_cpus_allowed <= 1); >>>> + >>>> + BUG_ON(!p->se.on_rq); >>>> + BUG_ON(!dl_task(p)); >>>> + >>>> + return p; >>>> +} >>>> + >>>> +/* >>>> + * See if the non running -deadline tasks on this rq >>>> + * can be sent to some other CPU where they can preempt >>>> + * and start executing. >>>> + */ >>>> +static int push_dl_task(struct rq *rq) >>>> +{ >>>> + struct task_struct *next_task; >>>> + struct rq *later_rq; >>>> + >>>> + if (!rq->dl.overloaded) >>>> + return 0; >>>> + >>>> + next_task = pick_next_pushable_dl_task(rq); >>>> + if (!next_task) >>>> + return 0; >>>> + >>>> +retry: >>>> + if (unlikely(next_task == rq->curr)) { >>>> + WARN_ON(1); >>>> + return 0; >>>> + } >>>> + >>>> + /* >>>> + * If next_task preempts rq->curr, and rq->curr >>>> + * can move away, it makes sense to just reschedule >>>> + * without going further in pushing next_task. >>>> + */ >>>> + if (dl_task(rq->curr) && >>>> + dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) && >>>> + rq->curr->nr_cpus_allowed > 1) { >>>> + resched_task(rq->curr); >>>> + return 0; >>>> + } >>>> + >>>> + /* We might release rq lock */ >>>> + get_task_struct(next_task); >>>> + >>>> + /* Will lock the rq it'll find */ >>>> + later_rq = find_lock_later_rq(next_task, rq); >>>> + if (!later_rq) { >>>> + struct task_struct *task; >>>> + >>>> + /* >>>> + * We must check all this again, since >>>> + * find_lock_later_rq releases rq->lock and it is >>>> + * then possible that next_task has migrated. >>>> + */ >>>> + task = pick_next_pushable_dl_task(rq); >>>> + if (task_cpu(next_task) == rq->cpu && task == next_task) { >>>> + /* >>>> + * The task is still there. We don't try >>>> + * again, some other cpu will pull it when ready. >>>> + */ >>>> + dequeue_pushable_dl_task(rq, next_task); >>>> + goto out; >>>> + } >>>> + >>>> + if (!task) >>>> + /* No more tasks */ >>>> + goto out; >>>> + >>>> + put_task_struct(next_task); >>>> + next_task = task; >>>> + goto retry; >>>> + } >>>> + >>>> + deactivate_task(rq, next_task, 0); >>>> + set_task_cpu(next_task, later_rq->cpu); >>>> + activate_task(later_rq, next_task, 0); >>>> + >>>> + resched_task(later_rq->curr); >>>> + >>>> + double_unlock_balance(rq, later_rq); >>>> + >>>> +out: >>>> + put_task_struct(next_task); >>>> + >>>> + return 1; >>>> +} >>>> + >>>> +static void push_dl_tasks(struct rq *rq) >>>> +{ >>>> + /* Terminates as it moves a -deadline task */ >>>> + while (push_dl_task(rq)) >>>> + ; >>>> +} >>>> + >>>> +static int pull_dl_task(struct rq *this_rq) >>>> +{ >>>> + int this_cpu = this_rq->cpu, ret = 0, cpu; >>>> + struct task_struct *p; >>>> + struct rq *src_rq; >>>> + u64 dmin = LONG_MAX; >>>> + >>>> + if (likely(!dl_overloaded(this_rq))) >>>> + return 0; >>>> + >>>> + /* >>>> + * Match the barrier from dl_set_overloaded; this guarantees that if we >>>> + * see overloaded we must also see the dlo_mask bit. >>>> + */ >>>> + smp_rmb(); >>>> + >>>> + for_each_cpu(cpu, this_rq->rd->dlo_mask) { >>>> + if (this_cpu == cpu) >>>> + continue; >>>> + >>>> + src_rq = cpu_rq(cpu); >>>> + >>>> + /* >>>> + * It looks racy, abd it is! However, as in sched_rt.c, >>> >>> abd it is? >>> >> >> Oops! >> >> Thanks, >> >> - Juri >> >>> >>>> + * we are fine with this. >>>> + */ >>>> + if (this_rq->dl.dl_nr_running && >>>> + dl_time_before(this_rq->dl.earliest_dl.curr, >>>> + src_rq->dl.earliest_dl.next)) >>>> + continue; >>>> + >>>> + /* Might drop this_rq->lock */ >>>> + double_lock_balance(this_rq, src_rq); >>>> + >>>> + /* >>>> + * If there are no more pullable tasks on the >>>> + * rq, we're done with it. >>>> + */ >>>> + if (src_rq->dl.dl_nr_running <= 1) >>>> + goto skip; >>>> + >>>> + p = pick_next_earliest_dl_task(src_rq, this_cpu); >>>> + >>>> + /* >>>> + * We found a task to be pulled if: >>>> + * - it preempts our current (if there's one), >>>> + * - it will preempt the last one we pulled (if any). >>>> + */ >>>> + if (p && dl_time_before(p->dl.deadline, dmin) && >>>> + (!this_rq->dl.dl_nr_running || >>>> + dl_time_before(p->dl.deadline, >>>> + this_rq->dl.earliest_dl.curr))) { >>>> + WARN_ON(p == src_rq->curr); >>>> + WARN_ON(!p->se.on_rq); >>>> + >>>> + /* >>>> + * Then we pull iff p has actually an earlier >>>> + * deadline than the current task of its runqueue. >>>> + */ >>>> + if (dl_time_before(p->dl.deadline, >>>> + src_rq->curr->dl.deadline)) >>>> + goto skip; >>>> + >>>> + ret = 1; >>>> + >>>> + deactivate_task(src_rq, p, 0); >>>> + set_task_cpu(p, this_cpu); >>>> + activate_task(this_rq, p, 0); >>>> + dmin = p->dl.deadline; >>>> + >>>> + /* Is there any other task even earlier? */ >>>> + } >>>> +skip: >>>> + double_unlock_balance(this_rq, src_rq); >>>> + } >>>> + >>>> + return ret; >>>> +} >>>> + >>>> +static void pre_schedule_dl(struct rq *rq, struct task_struct *prev) >>>> +{ >>>> + /* Try to pull other tasks here */ >>>> + if (dl_task(prev)) >>>> + pull_dl_task(rq); >>>> +} >>>> + >>>> +static void post_schedule_dl(struct rq *rq) >>>> +{ >>>> + push_dl_tasks(rq); >>>> +} >>>> + >>>> +/* >>>> + * Since the task is not running and a reschedule is not going to happen >>>> + * anytime soon on its runqueue, we try pushing it away now. >>>> + */ >>>> +static void task_woken_dl(struct rq *rq, struct task_struct *p) >>>> +{ >>>> + if (!task_running(rq, p) && >>>> + !test_tsk_need_resched(rq->curr) && >>>> + has_pushable_dl_tasks(rq) && >>>> + p->nr_cpus_allowed > 1 && >>>> + dl_task(rq->curr) && >>>> + (rq->curr->nr_cpus_allowed < 2 || >>>> + dl_entity_preempt(&rq->curr->dl, &p->dl))) { >>>> + push_dl_tasks(rq); >>>> + } >>>> +} >>>> + >>>> +static void set_cpus_allowed_dl(struct task_struct *p, >>>> + const struct cpumask *new_mask) >>>> +{ >>>> + struct rq *rq; >>>> + int weight; >>>> + >>>> + BUG_ON(!dl_task(p)); >>>> + >>>> + /* >>>> + * Update only if the task is actually running (i.e., >>>> + * it is on the rq AND it is not throttled). >>>> + */ >>>> + if (!on_dl_rq(&p->dl)) >>>> + return; >>>> + >>>> + weight = cpumask_weight(new_mask); >>>> + >>>> + /* >>>> + * Only update if the process changes its state from whether it >>>> + * can migrate or not. >>>> + */ >>>> + if ((p->nr_cpus_allowed > 1) == (weight > 1)) >>>> + return; >>>> + >>>> + rq = task_rq(p); >>>> + >>>> + /* >>>> + * The process used to be able to migrate OR it can now migrate >>>> + */ >>>> + if (weight <= 1) { >>>> + if (!task_current(rq, p)) >>>> + dequeue_pushable_dl_task(rq, p); >>>> + BUG_ON(!rq->dl.dl_nr_migratory); >>>> + rq->dl.dl_nr_migratory--; >>>> + } else { >>>> + if (!task_current(rq, p)) >>>> + enqueue_pushable_dl_task(rq, p); >>>> + rq->dl.dl_nr_migratory++; >>>> + } >>>> + >>>> + update_dl_migration(&rq->dl); >>>> +} >>>> + >>>> +/* Assumes rq->lock is held */ >>>> +static void rq_online_dl(struct rq *rq) >>>> +{ >>>> + if (rq->dl.overloaded) >>>> + dl_set_overload(rq); >>>> +} >>>> + >>>> +/* Assumes rq->lock is held */ >>>> +static void rq_offline_dl(struct rq *rq) >>>> +{ >>>> + if (rq->dl.overloaded) >>>> + dl_clear_overload(rq); >>>> +} >>>> + >>>> +void init_sched_dl_class(void) >>>> +{ >>>> + unsigned int i; >>>> + >>>> + for_each_possible_cpu(i) >>>> + zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i), >>>> + GFP_KERNEL, cpu_to_node(i)); >>>> +} >>>> + >>>> +#endif /* CONFIG_SMP */ >>>> + >>>> static void switched_from_dl(struct rq *rq, struct task_struct *p) >>>> { >>>> - if (hrtimer_active(&p->dl.dl_timer)) >>>> + if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy)) >>>> hrtimer_try_to_cancel(&p->dl.dl_timer); >>>> + >>>> +#ifdef CONFIG_SMP >>>> + /* >>>> + * Since this might be the only -deadline task on the rq, >>>> + * this is the right place to try to pull some other one >>>> + * from an overloaded cpu, if any. >>>> + */ >>>> + if (!rq->dl.dl_nr_running) >>>> + pull_dl_task(rq); >>>> +#endif >>>> } >>>> >>>> +/* >>>> + * When switching to -deadline, we may overload the rq, then >>>> + * we try to push someone off, if possible. >>>> + */ >>>> static void switched_to_dl(struct rq *rq, struct task_struct *p) >>>> { >>>> + int check_resched = 1; >>>> + >>>> /* >>>> * If p is throttled, don't consider the possibility >>>> * of preempting rq->curr, the check will be done right >>>> @@ -635,26 +1509,53 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) >>>> return; >>>> >>>> if (!p->on_rq || rq->curr != p) { >>>> - if (task_has_dl_policy(rq->curr)) >>>> +#ifdef CONFIG_SMP >>>> + if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p)) >>>> + /* Only reschedule if pushing failed */ >>>> + check_resched = 0; >>>> +#endif /* CONFIG_SMP */ >>>> + if (check_resched && task_has_dl_policy(rq->curr)) >>>> check_preempt_curr_dl(rq, p, 0); >>>> - else >>>> - resched_task(rq->curr); >>>> } >>>> } >>>> >>>> +/* >>>> + * If the scheduling parameters of a -deadline task changed, >>>> + * a push or pull operation might be needed. >>>> + */ >>>> static void prio_changed_dl(struct rq *rq, struct task_struct *p, >>>> int oldprio) >>>> { >>>> - switched_to_dl(rq, p); >>>> -} >>>> - >>>> + if (p->on_rq || rq->curr == p) { >>>> #ifdef CONFIG_SMP >>>> -static int >>>> -select_task_rq_dl(struct task_struct *p, int sd_flag, int flags) >>>> -{ >>>> - return task_cpu(p); >>>> + /* >>>> + * This might be too much, but unfortunately >>>> + * we don't have the old deadline value, and >>>> + * we can't argue if the task is increasing >>>> + * or lowering its prio, so... >>>> + */ >>>> + if (!rq->dl.overloaded) >>>> + pull_dl_task(rq); >>>> + >>>> + /* >>>> + * If we now have a earlier deadline task than p, >>>> + * then reschedule, provided p is still on this >>>> + * runqueue. >>>> + */ >>>> + if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) && >>>> + rq->curr == p) >>>> + resched_task(p); >>>> +#else >>>> + /* >>>> + * Again, we don't know if p has a earlier >>>> + * or later deadline, so let's blindly set a >>>> + * (maybe not needed) rescheduling point. >>>> + */ >>>> + resched_task(p); >>>> +#endif /* CONFIG_SMP */ >>>> + } else >>>> + switched_to_dl(rq, p); >>>> } >>>> -#endif >>>> >>>> const struct sched_class dl_sched_class = { >>>> .next = &rt_sched_class, >>>> @@ -669,6 +1570,12 @@ const struct sched_class dl_sched_class = { >>>> >>>> #ifdef CONFIG_SMP >>>> .select_task_rq = select_task_rq_dl, >>>> + .set_cpus_allowed = set_cpus_allowed_dl, >>>> + .rq_online = rq_online_dl, >>>> + .rq_offline = rq_offline_dl, >>>> + .pre_schedule = pre_schedule_dl, >>>> + .post_schedule = post_schedule_dl, >>>> + .task_woken = task_woken_dl, >>>> #endif >>>> >>>> .set_curr_task = set_curr_task_dl, >>>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c >>>> index 01970c8..f7c4881 100644 >>>> --- a/kernel/sched/rt.c >>>> +++ b/kernel/sched/rt.c >>>> @@ -1720,7 +1720,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p) >>>> !test_tsk_need_resched(rq->curr) && >>>> has_pushable_tasks(rq) && >>>> p->nr_cpus_allowed > 1 && >>>> - rt_task(rq->curr) && >>>> + (dl_task(rq->curr) || rt_task(rq->curr)) && >>>> (rq->curr->nr_cpus_allowed < 2 || >>>> rq->curr->prio <= p->prio)) >>>> push_rt_tasks(rq); >>>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >>>> index ba97476..70d0030 100644 >>>> --- a/kernel/sched/sched.h >>>> +++ b/kernel/sched/sched.h >>>> @@ -383,6 +383,31 @@ struct dl_rq { >>>> struct rb_node *rb_leftmost; >>>> >>>> unsigned long dl_nr_running; >>>> + >>>> +#ifdef CONFIG_SMP >>>> + /* >>>> + * Deadline values of the currently executing and the >>>> + * earliest ready task on this rq. Caching these facilitates >>>> + * the decision wether or not a ready but not running task >>>> + * should migrate somewhere else. >>>> + */ >>>> + struct { >>>> + u64 curr; >>>> + u64 next; >>>> + } earliest_dl; >>>> + >>>> + unsigned long dl_nr_migratory; >>>> + unsigned long dl_nr_total; >>>> + int overloaded; >>>> + >>>> + /* >>>> + * Tasks on this rq that can be pushed away. They are kept in >>>> + * an rb-tree, ordered by tasks' deadlines, with caching >>>> + * of the leftmost (earliest deadline) element. >>>> + */ >>>> + struct rb_root pushable_dl_tasks_root; >>>> + struct rb_node *pushable_dl_tasks_leftmost; >>>> +#endif >>>> }; >>>> >>>> #ifdef CONFIG_SMP >>>> @@ -403,6 +428,13 @@ struct root_domain { >>>> cpumask_var_t online; >>>> >>>> /* >>>> + * The bit corresponding to a CPU gets set here if such CPU has more >>>> + * than one runnable -deadline task (as it is below for RT tasks). >>>> + */ >>>> + cpumask_var_t dlo_mask; >>>> + atomic_t dlo_count; >>>> + >>>> + /* >>>> * The "RT overload" flag: it gets set if a CPU has more than >>>> * one runnable RT task. >>>> */ >>>> @@ -1063,6 +1095,8 @@ static inline void idle_balance(int cpu, struct rq *rq) >>>> extern void sysrq_sched_debug_show(void); >>>> extern void sched_init_granularity(void); >>>> extern void update_max_interval(void); >>>> + >>>> +extern void init_sched_dl_class(void); >>>> extern void init_sched_rt_class(void); >>>> extern void init_sched_fair_class(void); >>>> >>> >> >> >
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