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Commit e51fd5e2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: Fix wake_affine() vs RT tasks 



Mike reports that since e9e9250b (sched: Scale down cpu_power due to RT
tasks), wake_affine() goes funny on RT tasks due to them still having a
!0 weight and wake_affine() still subtracts that from the rq weight.

Since nobody should be using se->weight for RT tasks, set the value to
zero. Also, since we now use ->cpu_power to normalize rq weights to
account for RT cpu usage, add that factor into the imbalance computation.

Reported-by: default avatarMike Galbraith <efault@gmx.de>
Tested-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1275316109.27810.22969.camel@twins>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 54e88fad

kernel/sched.c

+6 −18
Original line number Diff line number Diff line
@@ -544,6 +544,8 @@ struct rq { 
	struct root_domain *rd;

	struct sched_domain *sd;



	unsigned long cpu_power;



	unsigned char idle_at_tick;

	/* For active balancing */

	int post_schedule;
@@ -1499,24 +1501,9 @@ static unsigned long target_load(int cpu, int type) 
	return max(rq->cpu_load[type-1], total);

}



static struct sched_group *group_of(int cpu)

{

	struct sched_domain *sd = rcu_dereference_sched(cpu_rq(cpu)->sd);



	if (!sd)

		return NULL;



	return sd->groups;

}



static unsigned long power_of(int cpu)

{

	struct sched_group *group = group_of(cpu);



	if (!group)

		return SCHED_LOAD_SCALE;



	return group->cpu_power;

	return cpu_rq(cpu)->cpu_power;

}



static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
@@ -1854,8 +1841,8 @@ static void dec_nr_running(struct rq *rq) 
static void set_load_weight(struct task_struct *p)

{

	if (task_has_rt_policy(p)) {

		p->se.load.weight = prio_to_weight[0] * 2;

		p->se.load.inv_weight = prio_to_wmult[0] >> 1;

		p->se.load.weight = 0;

		p->se.load.inv_weight = WMULT_CONST;

		return;

	}
@@ -7605,6 +7592,7 @@ void __init sched_init(void) 
#ifdef CONFIG_SMP

		rq->sd = NULL;

		rq->rd = NULL;

		rq->cpu_power = SCHED_LOAD_SCALE;

		rq->post_schedule = 0;

		rq->active_balance = 0;

		rq->next_balance = jiffies;

kernel/sched_fair.c

+16 −6
Original line number Diff line number Diff line
@@ -1225,7 +1225,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 
	unsigned long this_load, load;

	int idx, this_cpu, prev_cpu;

	unsigned long tl_per_task;

	unsigned int imbalance;

	struct task_group *tg;

	unsigned long weight;

	int balanced;
@@ -1252,8 +1251,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 
	tg = task_group(p);

	weight = p->se.load.weight;



	imbalance = 100 + (sd->imbalance_pct - 100) / 2;



	/*

	 * In low-load situations, where prev_cpu is idle and this_cpu is idle

	 * due to the sync cause above having dropped this_load to 0, we'll
@@ -1263,9 +1260,21 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 
	 * Otherwise check if either cpus are near enough in load to allow this

	 * task to be woken on this_cpu.

	 */

	balanced = !this_load ||

		100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=

		imbalance*(load + effective_load(tg, prev_cpu, 0, weight));

	if (this_load) {

		unsigned long this_eff_load, prev_eff_load;



		this_eff_load = 100;

		this_eff_load *= power_of(prev_cpu);

		this_eff_load *= this_load +

			effective_load(tg, this_cpu, weight, weight);



		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;

		prev_eff_load *= power_of(this_cpu);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);



		balanced = this_eff_load <= prev_eff_load;

	} else

		balanced = true;



	/*

	 * If the currently running task will sleep within
@@ -2298,6 +2307,7 @@ static void update_cpu_power(struct sched_domain *sd, int cpu) 
	if (!power)

		power = 1;



	cpu_rq(cpu)->cpu_power = power;

	sdg->cpu_power = power;

}