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sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks

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Remove the direct {push,pull} balancing operations from
switched_{from,to}_rt() / prio_changed_rt() and use the balance
callback queue.

Again, err on the side of too many reschedules; since too few is a
hard bug while too many is just annoying.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124742.766832367@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2015-06-11 14:46:41 +02:00 • committed by Thomas Gleixner
parent 8046d68062
commit fd7a4bed18
1 changed files with 19 additions and 16 deletions
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35
kernel/sched/rt.c
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@ -354,16 +354,23 @@ static inline int has_pushable_tasks(struct rq *rq)
return !plist_head_empty(&rq->rt.pushable_tasks); return !plist_head_empty(&rq->rt.pushable_tasks);
} }
static DEFINE_PER_CPU(struct callback_head, rt_balance_head); static DEFINE_PER_CPU(struct callback_head, rt_push_head);
static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
static void push_rt_tasks(struct rq *); static void push_rt_tasks(struct rq *);
static void pull_rt_task(struct rq *);
static inline void queue_push_tasks(struct rq *rq) static inline void queue_push_tasks(struct rq *rq)
{ {
if (!has_pushable_tasks(rq)) if (!has_pushable_tasks(rq))
return; return;
queue_balance_callback(rq, &per_cpu(rt_balance_head, rq->cpu), push_rt_tasks); queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
}
static inline void queue_pull_task(struct rq *rq)
{
queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
} }
static void enqueue_pushable_task(struct rq *rq, struct task_struct *p) static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
@ -2139,7 +2146,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
if (!task_on_rq_queued(p) || rq->rt.rt_nr_running) if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
return; return;
pull_rt_task(rq); queue_pull_task(rq);
} }
void __init init_sched_rt_class(void) void __init init_sched_rt_class(void)
@ -2160,8 +2167,6 @@ void __init init_sched_rt_class(void)
*/ */
static void switched_to_rt(struct rq *rq, struct task_struct *p) static void switched_to_rt(struct rq *rq, struct task_struct *p)
{ {
int check_resched = 1;
/* /*
* If we are already running, then there's nothing * If we are already running, then there's nothing
* that needs to be done. But if we are not running * that needs to be done. But if we are not running
@ -2171,13 +2176,12 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
*/ */
if (task_on_rq_queued(p) && rq->curr != p) { if (task_on_rq_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->rt.overloaded && if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
/* Don't resched if we changed runqueues */ queue_push_tasks(rq);
push_rt_task(rq) && rq != task_rq(p)) #else
check_resched = 0; if (p->prio < rq->curr->prio)
#endif /* CONFIG_SMP */
if (check_resched && p->prio < rq->curr->prio)
resched_curr(rq); resched_curr(rq);
#endif /* CONFIG_SMP */
} }
} }
@ -2198,14 +2202,13 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
* may need to pull tasks to this runqueue. * may need to pull tasks to this runqueue.
*/ */
if (oldprio < p->prio) if (oldprio < p->prio)
pull_rt_task(rq); queue_pull_task(rq);
/* /*
* If there's a higher priority task waiting to run * If there's a higher priority task waiting to run
* then reschedule. Note, the above pull_rt_task * then reschedule.
* 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.curr && rq->curr == p) if (p->prio > rq->rt.highest_prio.curr)
resched_curr(rq); resched_curr(rq);
#else #else
/* For UP simply resched on drop of prio */ /* For UP simply resched on drop of prio */