struct rt_prio_array active;
unsigned long rt_nr_running;
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
- int highest_prio; /* highest queued rt task prio */
+ struct {
+ int curr; /* highest queued rt task prio */
+ int next; /* next highest */
+ } highest_prio;
#endif
#ifdef CONFIG_SMP
unsigned long rt_nr_migratory;
int overloaded;
+ struct plist_head pushable_tasks;
#endif
int rt_throttled;
u64 rt_time;
#endif
+#ifdef CONFIG_PREEMPT
+
/*
- * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
+ * fair double_lock_balance: Safely acquires both rq->locks in a fair
+ * way at the expense of forcing extra atomic operations in all
+ * invocations. This assures that the double_lock is acquired using the
+ * same underlying policy as the spinlock_t on this architecture, which
+ * reduces latency compared to the unfair variant below. However, it
+ * also adds more overhead and therefore may reduce throughput.
*/
-static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
+static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
+ __releases(this_rq->lock)
+ __acquires(busiest->lock)
+ __acquires(this_rq->lock)
+{
+ spin_unlock(&this_rq->lock);
+ double_rq_lock(this_rq, busiest);
+
+ return 1;
+}
+
+#else
+/*
+ * Unfair double_lock_balance: Optimizes throughput at the expense of
+ * latency by eliminating extra atomic operations when the locks are
+ * already in proper order on entry. This favors lower cpu-ids and will
+ * grant the double lock to lower cpus over higher ids under contention,
+ * regardless of entry order into the function.
+ */
+static int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
__releases(this_rq->lock)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
int ret = 0;
- if (unlikely(!irqs_disabled())) {
- /* printk() doesn't work good under rq->lock */
- spin_unlock(&this_rq->lock);
- BUG_ON(1);
- }
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest < this_rq) {
spin_unlock(&this_rq->lock);
return ret;
}
+#endif /* CONFIG_PREEMPT */
+
+/*
+ * double_lock_balance - lock the busiest runqueue, this_rq is locked already.
+ */
+static int double_lock_balance(struct rq *this_rq, struct rq *busiest)
+{
+ if (unlikely(!irqs_disabled())) {
+ /* printk() doesn't work good under rq->lock */
+ spin_unlock(&this_rq->lock);
+ BUG_ON(1);
+ }
+
+ return _double_lock_balance(this_rq, busiest);
+}
+
static inline void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
__releases(busiest->lock)
{
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
#endif
+ plist_node_init(&p->pushable_tasks, MAX_PRIO);
+
put_cpu();
}
{
struct mm_struct *mm = rq->prev_mm;
long prev_state;
+#ifdef CONFIG_SMP
+ int post_schedule = 0;
+
+ if (current->sched_class->needs_post_schedule)
+ post_schedule = current->sched_class->needs_post_schedule(rq);
+#endif
rq->prev_mm = NULL;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
#ifdef CONFIG_SMP
- if (current->sched_class->post_schedule)
+ if (post_schedule)
current->sched_class->post_schedule(rq);
#endif
pulled++;
rem_load_move -= p->se.load.weight;
+#ifdef CONFIG_PREEMPT
+ /*
+ * NEWIDLE balancing is a source of latency, so preemptible kernels
+ * will stop after the first task is pulled to minimize the critical
+ * section.
+ */
+ if (idle == CPU_NEWLY_IDLE)
+ goto out;
+#endif
+
/*
* We only want to steal up to the prescribed amount of weighted load.
*/
sd, idle, all_pinned, &this_best_prio);
class = class->next;
+#ifdef CONFIG_PREEMPT
+ /*
+ * NEWIDLE balancing is a source of latency, so preemptible
+ * kernels will stop after the first task is pulled to minimize
+ * the critical section.
+ */
if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
break;
-
+#endif
} while (class && max_load_move > total_load_moved);
return total_load_moved > 0;
__set_bit(MAX_RT_PRIO, array->bitmap);
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
- rt_rq->highest_prio = MAX_RT_PRIO;
+ rt_rq->highest_prio.curr = MAX_RT_PRIO;
+ rt_rq->highest_prio.next = MAX_RT_PRIO;
#endif
#ifdef CONFIG_SMP
rt_rq->rt_nr_migratory = 0;
rt_rq->overloaded = 0;
+ plist_head_init(&rq->rt.pushable_tasks, &rq->lock);
#endif
rt_rq->rt_time = 0;
rq->rt.overloaded = 0;
}
}
+
+static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
+{
+ plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
+ plist_node_init(&p->pushable_tasks, p->prio);
+ plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
+}
+
+static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
+{
+ plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
+}
+
+#else
+
+#define enqueue_pushable_task(rq, p) do { } while (0)
+#define dequeue_pushable_task(rq, p) do { } while (0)
+
#endif /* CONFIG_SMP */
static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
if (rt_rq->rt_nr_running) {
if (rt_se && !on_rt_rq(rt_se))
enqueue_rt_entity(rt_se);
- if (rt_rq->highest_prio < curr->prio)
+ if (rt_rq->highest_prio.curr < curr->prio)
resched_task(curr);
}
}
struct rt_rq *rt_rq = group_rt_rq(rt_se);
if (rt_rq)
- return rt_rq->highest_prio;
+ return rt_rq->highest_prio.curr;
#endif
return rt_task_of(rt_se)->prio;
}
}
+#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
+
+static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu);
+
+static inline int next_prio(struct rq *rq)
+{
+ struct task_struct *next = pick_next_highest_task_rt(rq, rq->cpu);
+
+ if (next && rt_prio(next->prio))
+ return next->prio;
+ else
+ return MAX_RT_PRIO;
+}
+#endif
+
static inline
void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
- WARN_ON(!rt_prio(rt_se_prio(rt_se)));
- rt_rq->rt_nr_running++;
-#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
- if (rt_se_prio(rt_se) < rt_rq->highest_prio) {
+ int prio = rt_se_prio(rt_se);
#ifdef CONFIG_SMP
- struct rq *rq = rq_of_rt_rq(rt_rq);
+ struct rq *rq = rq_of_rt_rq(rt_rq);
#endif
- rt_rq->highest_prio = rt_se_prio(rt_se);
+ WARN_ON(!rt_prio(prio));
+ rt_rq->rt_nr_running++;
+#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
+ if (prio < rt_rq->highest_prio.curr) {
+
+ /*
+ * If the new task is higher in priority than anything on the
+ * run-queue, we have a new high that must be published to
+ * the world. We also know that the previous high becomes
+ * our next-highest.
+ */
+ rt_rq->highest_prio.next = rt_rq->highest_prio.curr;
+ rt_rq->highest_prio.curr = prio;
#ifdef CONFIG_SMP
if (rq->online)
- cpupri_set(&rq->rd->cpupri, rq->cpu,
- rt_se_prio(rt_se));
+ cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
#endif
- }
+ } else if (prio == rt_rq->highest_prio.curr)
+ /*
+ * If the next task is equal in priority to the highest on
+ * the run-queue, then we implicitly know that the next highest
+ * task cannot be any lower than current
+ */
+ rt_rq->highest_prio.next = prio;
+ else if (prio < rt_rq->highest_prio.next)
+ /*
+ * Otherwise, we need to recompute next-highest
+ */
+ rt_rq->highest_prio.next = next_prio(rq);
#endif
#ifdef CONFIG_SMP
- if (rt_se->nr_cpus_allowed > 1) {
- struct rq *rq = rq_of_rt_rq(rt_rq);
-
+ if (rt_se->nr_cpus_allowed > 1)
rq->rt.rt_nr_migratory++;
- }
- update_rt_migration(rq_of_rt_rq(rt_rq));
+ update_rt_migration(rq);
#endif
#ifdef CONFIG_RT_GROUP_SCHED
if (rt_se_boosted(rt_se))
void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
{
#ifdef CONFIG_SMP
- int highest_prio = rt_rq->highest_prio;
+ struct rq *rq = rq_of_rt_rq(rt_rq);
+ int highest_prio = rt_rq->highest_prio.curr;
#endif
WARN_ON(!rt_prio(rt_se_prio(rt_se)));
rt_rq->rt_nr_running--;
#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
if (rt_rq->rt_nr_running) {
- struct rt_prio_array *array;
+ int prio = rt_se_prio(rt_se);
- WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
- if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
- /* recalculate */
- array = &rt_rq->active;
- rt_rq->highest_prio =
+ WARN_ON(prio < rt_rq->highest_prio.curr);
+
+ /*
+ * This may have been our highest or next-highest priority
+ * task and therefore we may have some recomputation to do
+ */
+ if (prio == rt_rq->highest_prio.curr) {
+ struct rt_prio_array *array = &rt_rq->active;
+
+ rt_rq->highest_prio.curr =
sched_find_first_bit(array->bitmap);
- } /* otherwise leave rq->highest prio alone */
+ }
+
+ if (prio <= rt_rq->highest_prio.next)
+ rt_rq->highest_prio.next = next_prio(rq);
} else
- rt_rq->highest_prio = MAX_RT_PRIO;
+ rt_rq->highest_prio.curr = MAX_RT_PRIO;
#endif
#ifdef CONFIG_SMP
- if (rt_se->nr_cpus_allowed > 1) {
- struct rq *rq = rq_of_rt_rq(rt_rq);
+ if (rt_se->nr_cpus_allowed > 1)
rq->rt.rt_nr_migratory--;
- }
- if (rt_rq->highest_prio != highest_prio) {
- struct rq *rq = rq_of_rt_rq(rt_rq);
+ if (rq->online && rt_rq->highest_prio.curr != highest_prio)
+ cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
- if (rq->online)
- cpupri_set(&rq->rd->cpupri, rq->cpu,
- rt_rq->highest_prio);
- }
-
- update_rt_migration(rq_of_rt_rq(rt_rq));
+ update_rt_migration(rq);
#endif /* CONFIG_SMP */
#ifdef CONFIG_RT_GROUP_SCHED
if (rt_se_boosted(rt_se))
enqueue_rt_entity(rt_se);
+ if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
+ enqueue_pushable_task(rq, p);
+
inc_cpu_load(rq, p->se.load.weight);
}
update_curr_rt(rq);
dequeue_rt_entity(rt_se);
+ dequeue_pushable_task(rq, p);
+
dec_cpu_load(rq, p->se.load.weight);
}
return next;
}
-static struct task_struct *pick_next_task_rt(struct rq *rq)
+static struct task_struct *_pick_next_task_rt(struct rq *rq)
{
struct sched_rt_entity *rt_se;
struct task_struct *p;
p = rt_task_of(rt_se);
p->se.exec_start = rq->clock;
+
+ return p;
+}
+
+static struct task_struct *pick_next_task_rt(struct rq *rq)
+{
+ struct task_struct *p = _pick_next_task_rt(rq);
+
+ /* The running task is never eligible for pushing */
+ if (p)
+ dequeue_pushable_task(rq, p);
+
return p;
}
{
update_curr_rt(rq);
p->se.exec_start = 0;
+
+ /*
+ * The previous task needs to be made eligible for pushing
+ * if it is still active
+ */
+ if (p->se.on_rq && p->rt.nr_cpus_allowed > 1)
+ enqueue_pushable_task(rq, p);
}
#ifdef CONFIG_SMP
}
/* If this rq is still suitable use it. */
- if (lowest_rq->rt.highest_prio > task->prio)
+ if (lowest_rq->rt.highest_prio.curr > task->prio)
break;
/* try again */
return lowest_rq;
}
+static inline int has_pushable_tasks(struct rq *rq)
+{
+ return !plist_head_empty(&rq->rt.pushable_tasks);
+}
+
+static struct task_struct *pick_next_pushable_task(struct rq *rq)
+{
+ struct task_struct *p;
+
+ if (!has_pushable_tasks(rq))
+ return NULL;
+
+ p = plist_first_entry(&rq->rt.pushable_tasks,
+ struct task_struct, pushable_tasks);
+
+ BUG_ON(rq->cpu != task_cpu(p));
+ BUG_ON(task_current(rq, p));
+ BUG_ON(p->rt.nr_cpus_allowed <= 1);
+
+ BUG_ON(!p->se.on_rq);
+ BUG_ON(!rt_task(p));
+
+ return p;
+}
+
/*
* If the current CPU has more than one RT task, see if the non
* running task can migrate over to a CPU that is running a task
{
struct task_struct *next_task;
struct rq *lowest_rq;
- int ret = 0;
- int paranoid = RT_MAX_TRIES;
if (!rq->rt.overloaded)
return 0;
- next_task = pick_next_highest_task_rt(rq, -1);
+ next_task = pick_next_pushable_task(rq);
if (!next_task)
return 0;
struct task_struct *task;
/*
* find lock_lowest_rq releases rq->lock
- * so it is possible that next_task has changed.
- * If it has, then try again.
+ * so it is possible that next_task has migrated.
+ *
+ * We need to make sure that the task is still on the same
+ * run-queue and is also still the next task eligible for
+ * pushing.
*/
- task = pick_next_highest_task_rt(rq, -1);
- if (unlikely(task != next_task) && task && paranoid--) {
- put_task_struct(next_task);
- next_task = task;
- goto retry;
+ task = pick_next_pushable_task(rq);
+ if (task_cpu(next_task) == rq->cpu && task == next_task) {
+ /*
+ * If we get here, the task hasnt moved at all, but
+ * it has failed to push. We will not try again,
+ * since the other cpus will pull from us when they
+ * are ready.
+ */
+ dequeue_pushable_task(rq, next_task);
+ goto out;
}
- goto out;
+
+ if (!task)
+ /* No more tasks, just exit */
+ goto out;
+
+ /*
+ * Something has shifted, try again.
+ */
+ put_task_struct(next_task);
+ next_task = task;
+ goto retry;
}
deactivate_task(rq, next_task, 0);
double_unlock_balance(rq, lowest_rq);
- ret = 1;
out:
put_task_struct(next_task);
- return ret;
+ return 1;
}
-/*
- * TODO: Currently we just use the second highest prio task on
- * the queue, and stop when it can't migrate (or there's
- * no more RT tasks). There may be a case where a lower
- * priority RT task has a different affinity than the
- * higher RT task. In this case the lower RT task could
- * possibly be able to migrate where as the higher priority
- * RT task could not. We currently ignore this issue.
- * Enhancements are welcome!
- */
static void push_rt_tasks(struct rq *rq)
{
/* push_rt_task will return true if it moved an RT */
static int pull_rt_task(struct rq *this_rq)
{
int this_cpu = this_rq->cpu, ret = 0, cpu;
- struct task_struct *p, *next;
+ struct task_struct *p;
struct rq *src_rq;
if (likely(!rt_overloaded(this_rq)))
return 0;
- next = pick_next_task_rt(this_rq);
-
for_each_cpu(cpu, this_rq->rd->rto_mask) {
if (this_cpu == cpu)
continue;
src_rq = cpu_rq(cpu);
+
+ /*
+ * Don't bother taking the src_rq->lock if the next highest
+ * task is known to be lower-priority than our current task.
+ * This may look racy, but if this value is about to go
+ * logically higher, the src_rq will push this task away.
+ * And if its going logically lower, we do not care
+ */
+ if (src_rq->rt.highest_prio.next >=
+ this_rq->rt.highest_prio.curr)
+ continue;
+
/*
* We can potentially drop this_rq's lock in
* double_lock_balance, and another CPU could
- * steal our next task - hence we must cause
- * the caller to recalculate the next task
- * in that case:
+ * alter this_rq
*/
- if (double_lock_balance(this_rq, src_rq)) {
- struct task_struct *old_next = next;
-
- next = pick_next_task_rt(this_rq);
- if (next != old_next)
- ret = 1;
- }
+ double_lock_balance(this_rq, src_rq);
/*
* Are there still pullable RT tasks?
* Do we have an RT task that preempts
* the to-be-scheduled task?
*/
- if (p && (!next || (p->prio < next->prio))) {
+ if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
WARN_ON(p == src_rq->curr);
WARN_ON(!p->se.on_rq);
* This is just that p is wakeing up and hasn't
* had a chance to schedule. We only pull
* p if it is lower in priority than the
- * current task on the run queue or
- * this_rq next task is lower in prio than
- * the current task on that rq.
+ * current task on the run queue
*/
- if (p->prio < src_rq->curr->prio ||
- (next && next->prio < src_rq->curr->prio))
+ if (p->prio < src_rq->curr->prio)
goto skip;
ret = 1;
* case there's an even higher prio task
* in another runqueue. (low likelyhood
* but possible)
- *
- * Update next so that we won't pick a task
- * on another cpu with a priority lower (or equal)
- * than the one we just picked.
*/
- next = p;
-
}
skip:
double_unlock_balance(this_rq, src_rq);
static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
{
/* Try to pull RT tasks here if we lower this rq's prio */
- if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
+ if (unlikely(rt_task(prev)) && rq->rt.highest_prio.curr > prev->prio)
pull_rt_task(rq);
}
+/*
+ * assumes rq->lock is held
+ */
+static int needs_post_schedule_rt(struct rq *rq)
+{
+ return has_pushable_tasks(rq);
+}
+
static void post_schedule_rt(struct rq *rq)
{
/*
- * If we have more than one rt_task queued, then
- * see if we can push the other rt_tasks off to other CPUS.
- * Note we may release the rq lock, and since
- * the lock was owned by prev, we need to release it
- * first via finish_lock_switch and then reaquire it here.
+ * This is only called if needs_post_schedule_rt() indicates that
+ * we need to push tasks away
*/
- if (unlikely(rq->rt.overloaded)) {
- spin_lock_irq(&rq->lock);
- push_rt_tasks(rq);
- spin_unlock_irq(&rq->lock);
- }
+ spin_lock_irq(&rq->lock);
+ push_rt_tasks(rq);
+ spin_unlock_irq(&rq->lock);
}
/*
{
if (!task_running(rq, p) &&
!test_tsk_need_resched(rq->curr) &&
- rq->rt.overloaded)
+ has_pushable_tasks(rq) &&
+ p->rt.nr_cpus_allowed > 1)
push_rt_tasks(rq);
}
if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
struct rq *rq = task_rq(p);
+ if (!task_current(rq, p)) {
+ /*
+ * Make sure we dequeue this task from the pushable list
+ * before going further. It will either remain off of
+ * the list because we are no longer pushable, or it
+ * will be requeued.
+ */
+ if (p->rt.nr_cpus_allowed > 1)
+ dequeue_pushable_task(rq, p);
+
+ /*
+ * Requeue if our weight is changing and still > 1
+ */
+ if (weight > 1)
+ enqueue_pushable_task(rq, p);
+
+ }
+
if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
rq->rt.rt_nr_migratory++;
} else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
__enable_runtime(rq);
- cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
+ cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
}
/* Assumes rq->lock is held */
* can release the rq lock and p could migrate.
* Only reschedule if p is still on the same runqueue.
*/
- if (p->prio > rq->rt.highest_prio && rq->curr == p)
+ if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
resched_task(p);
#else
/* For UP simply resched on drop of prio */
struct task_struct *p = rq->curr;
p->se.exec_start = rq->clock;
+
+ /* The running task is never eligible for pushing */
+ dequeue_pushable_task(rq, p);
}
static const struct sched_class rt_sched_class = {
.rq_online = rq_online_rt,
.rq_offline = rq_offline_rt,
.pre_schedule = pre_schedule_rt,
+ .needs_post_schedule = needs_post_schedule_rt,
.post_schedule = post_schedule_rt,
.task_wake_up = task_wake_up_rt,
.switched_from = switched_from_rt,
projects / linux-2.6-omap-h63xx.git / commitdiff