sched/rt: Add rt_rq utilization tracking

schedutil governor relies on cfs_rq's util_avg to choose the OPP when CFS
tasks are running. When the CPU is overloaded by CFS and RT tasks, CFS tasks
are preempted by RT tasks and in this case util_avg reflects the remaining
capacity but not what CFS want to use. In such case, schedutil can select a
lower OPP whereas the CPU is overloaded. In order to have a more accurate
view of the utilization of the CPU, we track the utilization of RT tasks.
Only util_avg is correctly tracked but not load_avg and runnable_load_avg
which are useless for rt_rq.

rt_rq uses rq_clock_task and cfs_rq uses cfs_rq_clock_task but they are
the same at the root group level, so the PELT windows of the util_sum are
aligned.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: claudio@evidence.eu.com
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: patrick.bellasi@arm.com
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: valentin.schneider@arm.com
Cc: viresh.kumar@linaro.org
Link: http://lkml.kernel.org/r/1530200714-4504-3-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 00d6f2594c4e..405dd9ba6b39 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -594,6 +594,7 @@ struct rt_rq {
 	unsigned long		rt_nr_total;
 	int			overloaded;
 	struct plist_head	pushable_tasks;
+
 #endif /* CONFIG_SMP */
 	int			rt_queued;
 
@@ -854,6 +855,7 @@ struct rq {
 
 	u64			rt_avg;
 	u64			age_stamp;
+	struct sched_avg	avg_rt;
 	u64			idle_stamp;
 	u64			avg_idle;
 
@@ -2212,4 +2214,9 @@ static inline unsigned long cpu_util_cfs(struct rq *rq)
 
 	return util;
 }
+
+static inline unsigned long cpu_util_rt(struct rq *rq)
+{
+	return rq->avg_rt.util_avg;
+}
 #endif