sched/fair: Simplify the code of should_we_balance()

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

Signed-off-by: Peng Wang <rocking@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/245c792f0e580b3ca342ad61257f4c066ee0f84f.1586594833.git.rocking@linux.alibaba.com

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3d6ce75..63419c6 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9413,7 +9413,7 @@ 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
@@ -9434,18 +9434,12 @@ 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 of this group ? */
+       return group_balance_cpu(sg) == env->dst_cpu;
 }
 
 /*