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: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
klaby · May 9, 2012 · c22402a · c22402a
1 parent c82513e
commit c22402a
Showing 1 changed file with 5 additions and 5 deletions.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -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) {