Messages in this thread Patch in this message | | | Date | Fri, 6 Apr 2012 21:39:46 +0800 | Subject | Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic | From | Hillf Danton <> |
| |
Hello
On Fri, Apr 6, 2012 at 3:14 PM, Juri Lelli <juri.lelli@gmail.com> wrote: > Add dynamic migrations to SCHED_DEADLINE, so that tasks can > be moved among CPUs when necessary. It is also possible to bind a > task to a (set of) CPU(s), thus restricting its capability of > migrating, or forbidding migrations at all. > > The very same approach used in sched_rt is utilised: > - -deadline tasks are kept into CPU-specific runqueues, > - -deadline tasks are migrated among runqueues to achieve the > following: > * on an M-CPU system the M earliest deadline ready tasks > are always running; > * affinity/cpusets settings of all the -deadline tasks is > always respected. > > Therefore, this very special form of "load balancing" is done with > an active method, i.e., the scheduler pushes or pulls tasks between > runqueues when they are woken up and/or (de)scheduled. > IOW, every time a preemption occurs, the descheduled task might be sent > to some other CPU (depending on its deadline) to continue executing > (push). On the other hand, every time a CPU becomes idle, it might pull > the second earliest deadline ready task from some other CPU. > > To enforce this, a pull operation is always attempted before taking any > scheduling decision (pre_schedule()), as well as a push one after each > scheduling decision (post_schedule()). In addition, when a task arrives > or wakes up, the best CPU where to resume it is selected taking into > account its affinity mask, the system topology, but also its deadline. > E.g., from the scheduling point of view, the best CPU where to wake > up (and also where to push) a task is the one which is running the task > with the latest deadline among the M executing ones. > > In order to facilitate these decisions, per-runqueue "caching" of the > deadlines of the currently running and of the first ready task is used. > Queued but not running tasks are also parked in another rb-tree to > speed-up pushes. > > Signed-off-by: Juri Lelli <juri.lelli@gmail.com> > Signed-off-by: Dario Faggioli <raistlin@linux.it> > --- > kernel/sched_dl.c | 912 +++++++++++++++++++++++++++++++++++++++++++++++++++-- > kernel/sched_rt.c | 2 +- > 2 files changed, 889 insertions(+), 25 deletions(-) > > diff --git a/kernel/sched_dl.c b/kernel/sched_dl.c > index 604e2bc..38edefa 100644 > --- a/kernel/sched_dl.c > +++ b/kernel/sched_dl.c > @@ -10,6 +10,7 @@ > * miss some of their deadlines), and won't affect any other task. > * > * Copyright (C) 2010 Dario Faggioli <raistlin@linux.it>, > + * Juri Lelli <juri.lelli@gmail.com>, > * Michael Trimarchi <michael@amarulasolutions.com>, > * Fabio Checconi <fabio@gandalf.sssup.it> > */ > @@ -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); > @@ -50,6 +60,153 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq) > return dl_rq->rb_leftmost == &dl_se->rb_node; > } > > +#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). > + */ > + 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) > +{ > + dl_rq = &rq_of_dl_rq(dl_rq)->dl; > + > + dl_rq->dl_nr_total++; > + if (dl_se->nr_cpus_allowed > 1) > + dl_rq->dl_nr_migratory++; > + > + update_dl_migration(dl_rq);
if (dl_se->nr_cpus_allowed > 1) { dl_rq->dl_nr_migratory++; /* No change in migratory, no update of migration */ update_dl_migration(dl_rq); }
> +} > + > +static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) > +{ > + dl_rq = &rq_of_dl_rq(dl_rq)->dl; > + > + dl_rq->dl_nr_total--; > + if (dl_se->nr_cpus_allowed > 1) > + dl_rq->dl_nr_migratory--; > + > + update_dl_migration(dl_rq);
ditto
> +} > + > +/* > + * 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(&entry->dl, &p->dl))
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;
dl_rq->pushable_dl_tasks_leftmost = rb_next(&p->pushable_dl_tasks);
> + } > + > + 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);
return rq->dl.pushable_dl_tasks_leftmost != NULL; > +} > + > +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, > @@ -276,6 +433,14 @@ 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 (rq->dl.overloaded) if (has_pushable_dl_tasks(rq))
> + push_dl_task(rq); > +#endif > } > unlock: > task_rq_unlock(rq, p, &flags); > @@ -359,6 +524,100 @@ 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 int next_deadline(struct rq *rq) static inline typeof(next->dl.deadline) 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) void inc_dl_task(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) void dec_dl_task(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); > @@ -386,7 +645,7 @@ 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) > @@ -406,7 +665,7 @@ 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 > @@ -444,11 +703,15 @@ 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->dl.nr_cpus_allowed > 1) > + enqueue_pushable_dl_task(rq, p); > } > > 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) > @@ -480,6 +743,75 @@ 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; > + > + if (sd_flag != SD_BALANCE_WAKE) why is task_cpu(p) not eligible?
> + return smp_processor_id(); > + > + cpu = task_cpu(p); > + 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(rq->curr)) && the above ACCESS_ONCE for what? > + (rq->curr->dl.nr_cpus_allowed < 2 || > + dl_entity_preempt(&rq->curr->dl, &p->dl)) && !dl_entity_preempt(&p->dl, &rq->curr->dl)) && > + (p->dl.nr_cpus_allowed > 1)) { > + int target = find_later_rq(p); > + > + if (target != -1) > + cpu = target; > + } > + rcu_read_unlock(); > + > + return cpu; > +} > + > +static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) > +{ > + /* > + * Current can't be migrated, useles to reschedule, > + * let's hope p can move out. > + */ > + if (rq->curr->dl.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->dl.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. > @@ -487,8 +819,20 @@ 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_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()) please recheck !need_resched(), say rq->curr need reschedule? > + check_preempt_equal_dl(rq, p); > +#endif /* CONFIG_SMP */ > } > > #ifdef CONFIG_SCHED_HRTICK > @@ -532,10 +876,20 @@ struct task_struct *pick_next_task_dl(struct rq *rq) > > p = dl_task_of(dl_se); > p->se.exec_start = rq->clock; > + > + /* 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); need to check p is valid? > #endif > + > +#ifdef CONFIG_SMP > + rq->post_schedule = has_pushable_dl_tasks(rq); > +#endif /* CONFIG_SMP */ > + > return p; > } > > @@ -543,6 +897,9 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p) > { > update_curr_dl(rq); > p->se.exec_start = 0; why seset exec_start? > + > + if (on_dl_rq(&p->dl) && p->dl.nr_cpus_allowed > 1) > + enqueue_pushable_dl_task(rq, p); > } > > static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued) > @@ -576,43 +933,410 @@ static void set_curr_task_dl(struct rq *rq) > struct task_struct *p = rq->curr; > > p->se.exec_start = rq->clock; > + > + /* You can't push away the running task */ > + dequeue_pushable_dl_task(rq, p); > } > > -static void switched_from_dl(struct rq *rq, struct task_struct *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 (hrtimer_active(&p->dl.dl_timer)) > - hrtimer_try_to_cancel(&p->dl.dl_timer); > + if (!task_running(rq, p) && > + (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) && > + (p->dl.nr_cpus_allowed > 1)) > + return 1; > + > + return 0;
if (task_running(rq, p)) return 0; return cpumask_test_cpu(cpu, &p->cpus_allowed); that is all:) > } > > -static void switched_to_dl(struct rq *rq, struct task_struct *p) > +/* 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) { for_each_cpu_and(cpu, span, &task->cpus_allowed) { > + 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))) { please use dl_entity_preempt() > + 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)) { > + 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); please check is local_cpu_mask_dl valid
> + int this_cpu = smp_processor_id(); > + int best_cpu, cpu = task_cpu(task); > + > + if (task->dl.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 p is throttled, don't consider the possibility > - * of preempting rq->curr, the check will be done right > - * after its runtime will get replenished. > + * 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 (unlikely(p->dl.dl_throttled)) > - return; > + 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))) > + 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))) > + return best_cpu; > + } > + } > + rcu_read_unlock(); > > - if (!p->on_rq || rq->curr != p) { > - if (task_has_dl_policy(rq->curr)) > - check_preempt_curr_dl(rq, p, 0); > - else > - resched_task(rq->curr); > + /* > + * 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->se.on_rq)) { > + raw_spin_unlock(&later_rq->lock); > + 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 void prio_changed_dl(struct rq *rq, struct task_struct *p, > - int oldprio) > +static struct task_struct *pick_next_pushable_dl_task(struct rq *rq) > { > - switched_to_dl(rq, p); > + 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->dl.nr_cpus_allowed <= 1); > + > + BUG_ON(!p->se.on_rq); > + BUG_ON(!dl_task(p)); > + > + return p; > } > > -#ifdef CONFIG_SMP > -static int > -select_task_rq_dl(struct task_struct *p, int sd_flag, int flags) > +/* > + * 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) > { > - return task_cpu(p); > + 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->dl.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; > + > + 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, > + * 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->dl.nr_cpus_allowed > 1 && > + dl_task(rq->curr) && > + (rq->curr->dl.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, > @@ -622,10 +1346,145 @@ static void set_cpus_allowed_dl(struct task_struct *p, > > 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) && (weight != p->dl.nr_cpus_allowed)) { > + struct rq *rq = task_rq(p); > + > + if (!task_current(rq, p)) { > + /* > + * If the task was on the pushable list, > + * make sure it stays there only if the new > + * mask allows that. > + */ > + if (p->dl.nr_cpus_allowed > 1) > + dequeue_pushable_dl_task(rq, p); > + > + if (weight > 1) > + enqueue_pushable_dl_task(rq, p); > + } > + > + if ((p->dl.nr_cpus_allowed <= 1) && (weight > 1)) { > + rq->dl.dl_nr_migratory++; > + } else if ((p->dl.nr_cpus_allowed > 1) && (weight <= 1)) { > + BUG_ON(!rq->dl.dl_nr_migratory); > + rq->dl.dl_nr_migratory--; > + } > + > + update_dl_migration(&rq->dl); > + } > + > cpumask_copy(&p->cpus_allowed, new_mask); > p->dl.nr_cpus_allowed = weight; > } > + > +/* 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); > +} > + > +static inline 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) && !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 > + * after its runtime will get replenished. > + */ > + if (unlikely(p->dl.dl_throttled)) > + return; > + > + if (!p->on_rq || rq->curr != p) { > +#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); > + } > +} > + > +/* > + * 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) > +{ > + if (p->on_rq || rq->curr == p) { > +#ifdef CONFIG_SMP > + /* > + * 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); > +} > > static const struct sched_class dl_sched_class = { > .next = &rt_sched_class, > @@ -642,6 +1501,11 @@ static const struct sched_class dl_sched_class = { > .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 4b09704..7b609bc 100644 > --- a/kernel/sched_rt.c > +++ b/kernel/sched_rt.c > @@ -1590,7 +1590,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p) > !test_tsk_need_resched(rq->curr) && > has_pushable_tasks(rq) && > p->rt.nr_cpus_allowed > 1 && > - rt_task(rq->curr) && > + (dl_task(rq->curr) || rt_task(rq->curr)) && > (rq->curr->rt.nr_cpus_allowed < 2 || > rq->curr->prio <= p->prio)) > push_rt_tasks(rq); > -- > 1.7.5.4 >
Would you please mail me, in attachment, a monolithic patch of this work?
Thanks -hd
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