---

yaml
---
r: 76138
b: refs/heads/master
c: e1f47d8
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a22d7fc187ed996b66d8439db27b2303f79a8e7b
+refs/heads/master: e1f47d891c0f00769d6d40ac5740f943e998d089

trunk/kernel/sched_rt.c

@@ -160,11 +160,23 @@ static int select_task_rq_rt(struct task_struct *p, int sync)
 	struct rq *rq = task_rq(p);
 
 	/*
-	 * If the task will not preempt the RQ, try to find a better RQ
-	 * before we even activate the task
+	 * If the current task is an RT task, then
+	 * try to see if we can wake this RT task up on another
+	 * runqueue. Otherwise simply start this RT task
+	 * on its current runqueue.
+	 *
+	 * We want to avoid overloading runqueues. Even if
+	 * the RT task is of higher priority than the current RT task.
+	 * RT tasks behave differently than other tasks. If
+	 * one gets preempted, we try to push it off to another queue.
+	 * So trying to keep a preempting RT task on the same
+	 * cache hot CPU will force the running RT task to
+	 * a cold CPU. So we waste all the cache for the lower
+	 * RT task in hopes of saving some of a RT task
+	 * that is just being woken and probably will have
+	 * cold cache anyway.
 	 */
-	if ((p->prio >= rq->rt.highest_prio)
-	    && (p->nr_cpus_allowed > 1)) {
+	if (unlikely(rt_task(rq->curr))) {
 		int cpu = find_lowest_rq(p);
 
 		return (cpu == -1) ? task_cpu(p) : cpu;