sched: optimize siblings status check logic in wake_idle()

[powerpc.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index e4a5888..e60786e 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1406,7 +1406,16 @@ static int wake_idle(int cpu, struct task_struct *p)
        struct sched_domain *sd;
        int i;
 
-       if (idle_cpu(cpu))
+       /*
+        * If it is idle, then it is the best cpu to run this task.
+        *
+        * This cpu is also the best, if it has more than one task already.
+        * Siblings must be also busy(in most cases) as they didn't already
+        * pickup the extra load from this cpu and hence we need not check
+        * sibling runqueue info. This will avoid the checks and cache miss
+        * penalities associated with that.
+        */
+       if (idle_cpu(cpu) || cpu_rq(cpu)->nr_running > 1)
                return cpu;
 
        for_each_domain(cpu, sd) {