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Commit c22402a2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/fair: Let minimally loaded cpu balance the group 



Currently we let the leftmost (or first idle) cpu ascend the
sched_domain tree and perform load-balancing. The result is that the
busiest cpu in the group might be performing this function and pull
more load to itself. The next load balance pass will then try to
equalize this again.

Change this to pick the least loaded cpu to perform higher domain
balancing.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-v8zlrmgmkne3bkcy9dej1fvm@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c82513e5

kernel/sched/fair.c

+5 −5
Original line number Diff line number Diff line
@@ -3781,7 +3781,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, 
{

	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;

	int i;

	unsigned int balance_cpu = -1, first_idle_cpu = 0;

	unsigned int balance_cpu = -1;

	unsigned long balance_load = ~0UL;

	unsigned long avg_load_per_task = 0;



	if (local_group)
@@ -3797,12 +3798,11 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, 


		/* Bias balancing toward cpus of our domain */

		if (local_group) {

			if (idle_cpu(i) && !first_idle_cpu) {

				first_idle_cpu = 1;

			load = target_load(i, load_idx);

			if (load < balance_load || idle_cpu(i)) {

				balance_load = load;

				balance_cpu = i;

			}



			load = target_load(i, load_idx);

		} else {

			load = source_load(i, load_idx);

			if (load > max_cpu_load) {