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Commit bdb94aa5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Try to deal with low capacity 



When the capacity drops low, we want to migrate load away.
Allow the load-balancer to remove all tasks when we hit rock
bottom.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.342231003@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e9e9250b

kernel/sched.c

+28 −5
Original line number Original line Diff line number Diff line
@@ -3908,8 +3908,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, 
	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)

	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)

		sgs->group_imb = 1;

		sgs->group_imb = 1;





	sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;

	sgs->group_capacity =



		DIV_ROUND_CLOSEST(group->__cpu_power, SCHED_LOAD_SCALE);

}

}





/**

/**
@@ -3959,7 +3959,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, 
		 * and move all the excess tasks away.

		 * and move all the excess tasks away.

		 */

		 */

		if (prefer_sibling)

		if (prefer_sibling)

			sgs.group_capacity = 1;

			sgs.group_capacity = min(sgs.group_capacity, 1UL);





		if (local_group) {

		if (local_group) {

			sds->this_load = sgs.avg_load;

			sds->this_load = sgs.avg_load;
@@ -4191,6 +4191,26 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
	return NULL;

	return NULL;

}

}





static struct sched_group *group_of(int cpu)

{

	struct sched_domain *sd = rcu_dereference(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;

}



/*

/*

 * find_busiest_queue - find the busiest runqueue among the cpus in group.

 * find_busiest_queue - find the busiest runqueue among the cpus in group.

 */

 */
@@ -4203,15 +4223,18 @@ find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle, 
	int i;

	int i;





	for_each_cpu(i, sched_group_cpus(group)) {

	for_each_cpu(i, sched_group_cpus(group)) {

		unsigned long power = power_of(i);

		unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);

		unsigned long wl;

		unsigned long wl;





		if (!cpumask_test_cpu(i, cpus))

		if (!cpumask_test_cpu(i, cpus))

			continue;

			continue;





		rq = cpu_rq(i);

		rq = cpu_rq(i);

		wl = weighted_cpuload(i);

		wl = weighted_cpuload(i) * SCHED_LOAD_SCALE;

		wl /= power;





		if (rq->nr_running == 1 && wl > imbalance)

		if (capacity && rq->nr_running == 1 && wl > imbalance)

			continue;

			continue;





		if (wl > max_load) {

		if (wl > max_load) {