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Commit 408ed066 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: hierarchical load vs find_busiest_group 



find_busiest_group() has some assumptions about task weight being in the
NICE_0_LOAD range. Hierarchical task groups break this assumption - fix this
by replacing it with the average task weight, which will adapt the situation.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bb3469ac

kernel/sched.c

+23 −3
Original line number Diff line number Diff line
@@ -3050,6 +3050,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
	max_load = this_load = total_load = total_pwr = 0;

	busiest_load_per_task = busiest_nr_running = 0;

	this_load_per_task = this_nr_running = 0;



	if (idle == CPU_NOT_IDLE)

		load_idx = sd->busy_idx;

	else if (idle == CPU_NEWLY_IDLE)
@@ -3064,6 +3065,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
		int __group_imb = 0;

		unsigned int balance_cpu = -1, first_idle_cpu = 0;

		unsigned long sum_nr_running, sum_weighted_load;

		unsigned long sum_avg_load_per_task;

		unsigned long avg_load_per_task;



		local_group = cpu_isset(this_cpu, group->cpumask);
@@ -3072,6 +3075,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 


		/* Tally up the load of all CPUs in the group */

		sum_weighted_load = sum_nr_running = avg_load = 0;

		sum_avg_load_per_task = avg_load_per_task = 0;



		max_cpu_load = 0;

		min_cpu_load = ~0UL;
@@ -3105,6 +3110,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
			avg_load += load;

			sum_nr_running += rq->nr_running;

			sum_weighted_load += weighted_cpuload(i);



			sum_avg_load_per_task += cpu_avg_load_per_task(i);

		}



		/*
@@ -3126,7 +3133,20 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
		avg_load = sg_div_cpu_power(group,

				avg_load * SCHED_LOAD_SCALE);



		if ((max_cpu_load - min_cpu_load) > SCHED_LOAD_SCALE)



		/*

		 * Consider the group unbalanced when the imbalance is larger

		 * than the average weight of two tasks.

		 *

		 * APZ: with cgroup the avg task weight can vary wildly and

		 *      might not be a suitable number - should we keep a

		 *      normalized nr_running number somewhere that negates

		 *      the hierarchy?

		 */

		avg_load_per_task = sg_div_cpu_power(group,

				sum_avg_load_per_task * SCHED_LOAD_SCALE);



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

			__group_imb = 1;



		group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
@@ -3267,9 +3287,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
			if (busiest_load_per_task > this_load_per_task)

				imbn = 1;

		} else

			this_load_per_task = SCHED_LOAD_SCALE;

			this_load_per_task = cpu_avg_load_per_task(this_cpu);



		if (max_load - this_load + SCHED_LOAD_SCALE_FUZZ >=

		if (max_load - this_load + 2*busiest_load_per_task >=

					busiest_load_per_task * imbn) {

			*imbalance = busiest_load_per_task;

			return busiest;