Messages in this thread Patch in this message | | | Date | Wed, 20 Nov 2013 13:51:34 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic. |
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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.
> + 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(...)) { ... } }
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.
We should be able to incorporate cpuprio_find() to be dl aware too. That is, work for both -rt and -dl.
> + 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?
:-)
-- Steve
> + * 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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