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Commit ac086bc2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: rt-group: smp balancing 



Currently the rt group scheduling does a per cpu runtime limit, however
the rt load balancer makes no guarantees about an equal spread of real-
time tasks, just that at any one time, the highest priority tasks run.

Solve this by making the runtime limit a global property by borrowing
excessive runtime from the other cpus once the local limit runs out.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d0b27fa7

kernel/sched.c

+37 −3
Original line number Diff line number Diff line
@@ -164,6 +164,7 @@ struct rt_prio_array { 
struct rt_bandwidth {

	ktime_t rt_period;

	u64 rt_runtime;

	spinlock_t rt_runtime_lock;

	struct hrtimer rt_period_timer;

};
@@ -198,6 +199,8 @@ void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime) 
	rt_b->rt_period = ns_to_ktime(period);

	rt_b->rt_runtime = runtime;



	spin_lock_init(&rt_b->rt_runtime_lock);



	hrtimer_init(&rt_b->rt_period_timer,

			CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	rt_b->rt_period_timer.function = sched_rt_period_timer;
@@ -414,6 +417,8 @@ struct rt_rq { 
#endif

	int rt_throttled;

	u64 rt_time;

	u64 rt_runtime;

	spinlock_t rt_runtime_lock;



#ifdef CONFIG_RT_GROUP_SCHED

	unsigned long rt_nr_boosted;
@@ -7299,6 +7304,8 @@ static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq) 


	rt_rq->rt_time = 0;

	rt_rq->rt_throttled = 0;

	rt_rq->rt_runtime = 0;

	spin_lock_init(&rt_rq->rt_runtime_lock);



#ifdef CONFIG_RT_GROUP_SCHED

	rt_rq->rt_nr_boosted = 0;
@@ -7335,6 +7342,7 @@ static void init_tg_rt_entry(struct rq *rq, struct task_group *tg, 
	init_rt_rq(rt_rq, rq);

	rt_rq->tg = tg;

	rt_rq->rt_se = rt_se;

	rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;

	if (add)

		list_add(&rt_rq->leaf_rt_rq_list, &rq->leaf_rt_rq_list);
@@ -7391,6 +7399,8 @@ void __init sched_init(void) 
		init_tg_rt_entry(rq, &init_task_group,

				&per_cpu(init_rt_rq, i),

				&per_cpu(init_sched_rt_entity, i), i, 1);

#else

		rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;

#endif



		for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@@ -7974,11 +7984,11 @@ static inline int tg_has_rt_tasks(struct task_group *tg) 
static int tg_set_bandwidth(struct task_group *tg,

		u64 rt_period, u64 rt_runtime)

{

	int err = 0;

	int i, err = 0;



	mutex_lock(&rt_constraints_mutex);

	read_lock(&tasklist_lock);

	if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) {

	if (rt_runtime == 0 && tg_has_rt_tasks(tg)) {

		err = -EBUSY;

		goto unlock;

	}
@@ -7986,8 +7996,19 @@ static int tg_set_bandwidth(struct task_group *tg, 
		err = -EINVAL;

		goto unlock;

	}



	spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);

	tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);

	tg->rt_bandwidth.rt_runtime = rt_runtime;



	for_each_possible_cpu(i) {

		struct rt_rq *rt_rq = tg->rt_rq[i];



		spin_lock(&rt_rq->rt_runtime_lock);

		rt_rq->rt_runtime = rt_runtime;

		spin_unlock(&rt_rq->rt_runtime_lock);

	}

	spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);

 unlock:

	read_unlock(&tasklist_lock);

	mutex_unlock(&rt_constraints_mutex);
@@ -8052,6 +8073,19 @@ static int sched_rt_global_constraints(void) 
#else

static int sched_rt_global_constraints(void)

{

	unsigned long flags;

	int i;



	spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);

	for_each_possible_cpu(i) {

		struct rt_rq *rt_rq = &cpu_rq(i)->rt;



		spin_lock(&rt_rq->rt_runtime_lock);

		rt_rq->rt_runtime = global_rt_runtime();

		spin_unlock(&rt_rq->rt_runtime_lock);

	}

	spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);



	return 0;

}

#endif
@@ -8168,7 +8202,7 @@ static u64 cpu_shares_read_uint(struct cgroup *cgrp, struct cftype *cft) 
#endif



#ifdef CONFIG_RT_GROUP_SCHED

static int cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,

static ssize_t cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,

				struct file *file,

				const char __user *userbuf,

				size_t nbytes, loff_t *unused_ppos)

kernel/sched_rt.c

+85 −3
Original line number Diff line number Diff line
@@ -62,7 +62,12 @@ static inline u64 sched_rt_runtime(struct rt_rq *rt_rq) 
	if (!rt_rq->tg)

		return RUNTIME_INF;



	return rt_rq->tg->rt_bandwidth.rt_runtime;

	return rt_rq->rt_runtime;

}



static inline u64 sched_rt_period(struct rt_rq *rt_rq)

{

	return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);

}



#define for_each_leaf_rt_rq(rt_rq, rq) \
@@ -145,11 +150,21 @@ struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu) 
	return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];

}



static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)

{

	return &rt_rq->tg->rt_bandwidth;

}



#else



static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)

{

	return def_rt_bandwidth.rt_runtime;

	return rt_rq->rt_runtime;

}



static inline u64 sched_rt_period(struct rt_rq *rt_rq)

{

	return ktime_to_ns(def_rt_bandwidth.rt_period);

}



#define for_each_leaf_rt_rq(rt_rq, rq) \
@@ -200,6 +215,11 @@ struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu) 
	return &cpu_rq(cpu)->rt;

}



static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)

{

	return &def_rt_bandwidth;

}



#endif



static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
@@ -218,8 +238,10 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) 


		spin_lock(&rq->lock);

		if (rt_rq->rt_time) {

			u64 runtime = rt_b->rt_runtime;

			u64 runtime;



			spin_lock(&rt_rq->rt_runtime_lock);

			runtime = rt_rq->rt_runtime;

			rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);

			if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {

				rt_rq->rt_throttled = 0;
@@ -227,6 +249,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) 
			}

			if (rt_rq->rt_time || rt_rq->rt_nr_running)

				idle = 0;

			spin_unlock(&rt_rq->rt_runtime_lock);

		}



		if (enqueue)
@@ -237,6 +260,47 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) 
	return idle;

}



#ifdef CONFIG_SMP

static int balance_runtime(struct rt_rq *rt_rq)

{

	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

	struct root_domain *rd = cpu_rq(smp_processor_id())->rd;

	int i, weight, more = 0;

	u64 rt_period;



	weight = cpus_weight(rd->span);



	spin_lock(&rt_b->rt_runtime_lock);

	rt_period = ktime_to_ns(rt_b->rt_period);

	for_each_cpu_mask(i, rd->span) {

		struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);

		s64 diff;



		if (iter == rt_rq)

			continue;



		spin_lock(&iter->rt_runtime_lock);

		diff = iter->rt_runtime - iter->rt_time;

		if (diff > 0) {

			do_div(diff, weight);

			if (rt_rq->rt_runtime + diff > rt_period)

				diff = rt_period - rt_rq->rt_runtime;

			iter->rt_runtime -= diff;

			rt_rq->rt_runtime += diff;

			more = 1;

			if (rt_rq->rt_runtime == rt_period) {

				spin_unlock(&iter->rt_runtime_lock);

				break;

			}

		}

		spin_unlock(&iter->rt_runtime_lock);

	}

	spin_unlock(&rt_b->rt_runtime_lock);



	return more;

}

#endif



static inline int rt_se_prio(struct sched_rt_entity *rt_se)

{

#ifdef CONFIG_RT_GROUP_SCHED
@@ -259,6 +323,22 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq) 
	if (rt_rq->rt_throttled)

		return rt_rq_throttled(rt_rq);



	if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))

		return 0;



#ifdef CONFIG_SMP

	if (rt_rq->rt_time > runtime) {

		int more;



		spin_unlock(&rt_rq->rt_runtime_lock);

		more = balance_runtime(rt_rq);

		spin_lock(&rt_rq->rt_runtime_lock);



		if (more)

			runtime = sched_rt_runtime(rt_rq);

	}

#endif



	if (rt_rq->rt_time > runtime) {

		rt_rq->rt_throttled = 1;

		if (rt_rq_throttled(rt_rq)) {
@@ -294,9 +374,11 @@ static void update_curr_rt(struct rq *rq) 
	curr->se.exec_start = rq->clock;

	cpuacct_charge(curr, delta_exec);



	spin_lock(&rt_rq->rt_runtime_lock);

	rt_rq->rt_time += delta_exec;

	if (sched_rt_runtime_exceeded(rt_rq))

		resched_task(curr);

	spin_unlock(&rt_rq->rt_runtime_lock);

}



static inline