linux-kernel - [PATCH RFC 2/8] sched/deadline: move cpu frequency selection triggering points

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Message-Id: <20170523085351.18586-3-juri.lelli@arm.com>
Date:   Tue, 23 May 2017 09:53:45 +0100
From:   Juri Lelli <juri.lelli@....com>
To:     peterz@...radead.org, mingo@...hat.com, rjw@...ysocki.net,
        viresh.kumar@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        tglx@...utronix.de, vincent.guittot@...aro.org,
        rostedt@...dmis.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, tkjos@...roid.com,
        joelaf@...gle.com, andresoportus@...gle.com,
        morten.rasmussen@....com, dietmar.eggemann@....com,
        patrick.bellasi@....com, juri.lelli@....com,
        Ingo Molnar <mingo@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH RFC 2/8] sched/deadline: move cpu frequency selection triggering points

Since SCHED_DEADLINE doesn't track utilization signal (but reserves a
fraction of CPU bandwidth to tasks admitted to the system), there is no
point in evaluating frequency changes during each tick event.

Move frequency selection triggering points to where running_bw changes.

Co-authored-by: Claudio Scordino <claudio@...dence.eu.com>
Signed-off-by: Juri Lelli <juri.lelli@....com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Luca Abeni <luca.abeni@...tannapisa.it>
---
 kernel/sched/deadline.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1da44b36fae0..fed54b078240 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -52,6 +52,8 @@ void add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 	dl_rq->running_bw += dl_bw;
 	SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
 	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
+	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
+	cpufreq_update_this_cpu(rq_of_dl_rq(dl_rq), SCHED_CPUFREQ_DL);
 }
 
 static inline
@@ -64,6 +66,8 @@ void sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 	SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
 	if (dl_rq->running_bw > old)
 		dl_rq->running_bw = 0;
+	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
+	cpufreq_update_this_cpu(rq_of_dl_rq(dl_rq), SCHED_CPUFREQ_DL);
 }
 
 static inline
@@ -1021,9 +1025,6 @@ static void update_curr_dl(struct rq *rq)
 		return;
 	}
 
-	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
-	cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_DL);
-
 	schedstat_set(curr->se.statistics.exec_max,
 		      max(curr->se.statistics.exec_max, delta_exec));
 
-- 
2.11.0