[tip:sched/core] sched/cpufreq: Always consider all CPUs when deciding next freq

[tip-bot for Juri Lelli <tipbot@zytor.com>]

Commit-ID:  0fa7d181f1a60149061632266bb432b4b61acdac
Gitweb:     https://git.kernel.org/tip/0fa7d181f1a60149061632266bb432b4b61acdac
Author:     Juri Lelli <juri.lelli@arm.com>
AuthorDate: Mon, 4 Dec 2017 11:23:22 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 10 Jan 2018 12:53:34 +0100

sched/cpufreq: Always consider all CPUs when deciding next freq

No assumption can be made upon the rate at which frequency updates get
triggered, as there are scheduling policies (like SCHED_DEADLINE) which
don't trigger them so frequently.

Remove such assumption from the code, by always considering
SCHED_DEADLINE utilization signal as not stale.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: alessio.balsini@arm.com
Cc: bristot@redhat.com
Cc: dietmar.eggemann@arm.com
Cc: joelaf@google.com
Cc: juri.lelli@redhat.com
Cc: mathieu.poirier@linaro.org
Cc: morten.rasmussen@arm.com
Cc: patrick.bellasi@arm.com
Cc: rjw@rjwysocki.net
Cc: rostedt@goodmis.org
Cc: tkjos@android.com
Cc: tommaso.cucinotta@santannapisa.it
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/20171204102325.5110-6-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/cpufreq_schedutil.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index e9e0713..dd062a1 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -315,17 +315,21 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
 		s64 delta_ns;
 
 		/*
-		 * If the CPU utilization was last updated before the previous
-		 * frequency update and the time elapsed between the last update
-		 * of the CPU utilization and the last frequency update is long
-		 * enough, don't take the CPU into account as it probably is
-		 * idle now (and clear iowait_boost for it).
+		 * If the CFS CPU utilization was last updated before the
+		 * previous frequency update and the time elapsed between the
+		 * last update of the CPU utilization and the last frequency
+		 * update is long enough, reset iowait_boost and util_cfs, as
+		 * they are now probably stale. However, still consider the
+		 * CPU contribution if it has some DEADLINE utilization
+		 * (util_dl).
 		 */
 		delta_ns = time - j_sg_cpu->last_update;
 		if (delta_ns > TICK_NSEC) {
 			j_sg_cpu->iowait_boost = 0;
 			j_sg_cpu->iowait_boost_pending = false;
-			continue;
+			j_sg_cpu->util_cfs = 0;
+			if (j_sg_cpu->util_dl == 0)
+				continue;
 		}
 		if (j_sg_cpu->flags & SCHED_CPUFREQ_RT)
 			return policy->cpuinfo.max_freq;