[PATCH v2] sched/fair: Simplify the code of should_we_balance()

[Peng Wang]

We only consider group_balance_cpu() after there is no idle
cpu. So, just do comparison before return at these two cases.

Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peng Wang <rocking@xxxxxxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 02f323b..c3f57f4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9409,7 +9409,7 @@ static int active_load_balance_cpu_stop(void *data);
 static int should_we_balance(struct lb_env *env)
 {
 	struct sched_group *sg = env->sd->groups;
-	int cpu, balance_cpu = -1;
+	int cpu;
 
 	/*
 	 * Ensure the balancing environment is consistent; can happen
@@ -9430,18 +9430,12 @@ static int should_we_balance(struct lb_env *env)
 		if (!idle_cpu(cpu))
 			continue;
 
-		balance_cpu = cpu;
-		break;
+		/* Are we the first idle CPU? */
+		return cpu == env->dst_cpu;
 	}
 
-	if (balance_cpu == -1)
-		balance_cpu = group_balance_cpu(sg);
-
-	/*
-	 * First idle CPU or the first CPU(busiest) in this sched group
-	 * is eligible for doing load balancing at this and above domains.
-	 */
-	return balance_cpu == env->dst_cpu;
+	/* Are we the first CPU in the balance mask of this group? */
+	return group_balance_cpu(sg) == env->dst_cpu;
 }
 
 /*
-- 
2.9.5