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Message-ID: <4F7F285A.1010703@gmail.com>
Date: Fri, 06 Apr 2012 19:31:06 +0200
From: Juri Lelli <juri.lelli@...il.com>
To: Hillf Danton <dhillf@...il.com>
CC: peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
rostedt@...dmis.org, cfriesen@...tel.com, oleg@...hat.com,
fweisbec@...il.com, darren@...art.com, johan.eker@...csson.com,
p.faure@...tech.ch, linux-kernel@...r.kernel.org,
claudio@...dence.eu.com, michael@...rulasolutions.com,
fcheccon@...per.es
Subject: Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic
Hi,
On 04/06/2012 03:39 PM, Hillf Danton wrote:
> Hello
>
> On Fri, Apr 6, 2012 at 3:14 PM, Juri Lelli<juri.lelli@...il.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@...il.com>
>> Signed-off-by: Dario Faggioli<raistlin@...ux.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@...ux.it>,
>> + * Juri Lelli<juri.lelli@...il.com>,
>> * Michael Trimarchi<michael@...rulasolutions.com>,
>> * Fabio Checconi<fabio@...dalf.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);
> }
>
I think the code is probably cleaner as it is written now and aligned with
sched_rt.
>> +}
>> +
>> +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
>
As above.
>> +}
>> +
>> +/*
>> + * 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))
>
Any specific reason to reverse the condition?
>> + 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);
>
Yes, but mine is probably cleaner :-).
>> + }
>> +
>> + 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;
Equivalent?
>> +}
>> +
>> +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))
>
Ok, better.
>> + 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) ?
>
Right!
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)
> void inc_dl_task(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
>
Well, I see this as "increment the number of -dl tasks"..
>> +{
>> + 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)
>
Like above.
>> +{
>> + 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?
>
Right, I'll change this.
>> + 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?
Yes, I'll change this.
>> + (rq->curr->dl.nr_cpus_allowed< 2 ||
>> + dl_entity_preempt(&rq->curr->dl,&p->dl))&&
> !dl_entity_preempt(&p->dl,&rq->curr->dl))&&
As above?
>> + (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))
Ok.
>> 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?
Sorry, I don't get this..
>> + 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?
I'll restructure pick_next_task_ as in sched_rt.
>> #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?
Good point, I'll probably remove this.
>> +
>> + 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:)
We use this inside pull_dl_task. Since we are searching for a task to
pull, you must be sure that the found task can actually migrate checking
nr_cpus_allowed > 1.
>> }
>>
>> -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()
Well, ok with this and above. Anyway this code is completely removed in 15/16.
>> + 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
>
Could you explain more why should I check for validity?
>> + 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?
>
Ok, I'll prepare the monolithic patch and probably store it somewhere so that it
can be downloaded also by others.
Thanks a lot for the immediate review :-)!
Best Regards,
- Juri
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