sched: Account rr tasks

fweisbec · fweisbec · commit 01d36d0ac390 · 2016-03-02T16:43:04.000+01:00
In order to evaluate the scheduler tick dependency without probing
context switches, we need to know how much SCHED_RR and SCHED_FIFO tasks
are enqueued as those policies don't have the same preemption
requirements.

To prepare for that, let's account SCHED_RR tasks, we'll be able to
deduce SCHED_FIFO tasks as well from it and the total RT tasks in the
runqueue.

Reviewed-by: Chris Metcalf &lt;cmetcalf@ezchip.com&gt;
Cc: Christoph Lameter &lt;cl@linux.com&gt;
Cc: Chris Metcalf &lt;cmetcalf@ezchip.com&gt;
Cc: Ingo Molnar &lt;mingo@kernel.org&gt;
Cc: Luiz Capitulino &lt;lcapitulino@redhat.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Rik van Riel &lt;riel@redhat.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Viresh Kumar &lt;viresh.kumar@linaro.org&gt;
Signed-off-by: Frederic Weisbecker &lt;fweisbec@gmail.com&gt;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
@@ -1141,13 +1141,28 @@ unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
 		return 1;
 }
 
+static inline
+unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
+{
+	struct rt_rq *group_rq = group_rt_rq(rt_se);
+	struct task_struct *tsk;
+
+	if (group_rq)
+		return group_rq->rr_nr_running;
+
+	tsk = rt_task_of(rt_se);
+
+	return (tsk->policy == SCHED_RR) ? 1 : 0;
+}
+
 static inline
 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 {
 	int prio = rt_se_prio(rt_se);
 
 	WARN_ON(!rt_prio(prio));
 	rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
+	rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
 
 	inc_rt_prio(rt_rq, prio);
 	inc_rt_migration(rt_se, rt_rq);
@@ -1160,6 +1175,7 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 	WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 	WARN_ON(!rt_rq->rt_nr_running);
 	rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
+	rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
 
 	dec_rt_prio(rt_rq, rt_se_prio(rt_se));
 	dec_rt_migration(rt_se, rt_rq);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
@@ -450,6 +450,7 @@ static inline int rt_bandwidth_enabled(void)
 struct rt_rq {
 	struct rt_prio_array active;
 	unsigned int rt_nr_running;
+	unsigned int rr_nr_running;
 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 	struct {
 		int curr; /* highest queued rt task prio */
