linux-kernel - [tip:sched/core] sched/fair: Call cpufreq update util handlers less frequently on UP

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Message-ID: <tip-a030d7381d8b3adabde724e3077bb6cb32d1b3ee@git.kernel.org>
Date:   Thu, 10 Aug 2017 05:03:42 -0700
From:   tip-bot for Viresh Kumar <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, vincent.guittot@...aro.org,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, hpa@...or.com, peterz@...radead.org,
        viresh.kumar@...aro.org
Subject: [tip:sched/core] sched/fair: Call cpufreq update util handlers less
 frequently on UP

Commit-ID:  a030d7381d8b3adabde724e3077bb6cb32d1b3ee
Gitweb:     http://git.kernel.org/tip/a030d7381d8b3adabde724e3077bb6cb32d1b3ee
Author:     Viresh Kumar <viresh.kumar@...aro.org>
AuthorDate: Wed, 24 May 2017 10:59:52 +0530
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:18:09 +0200

sched/fair: Call cpufreq update util handlers less frequently on UP

For SMP systems, update_load_avg() calls the cpufreq update util
handlers only for the top level cfs_rq (i.e. rq->cfs).

But that is not the case for UP systems. update_load_avg() calls util
handler for any cfs_rq for which it is called. This would result in way
too many calls from the scheduler to the cpufreq governors when
CONFIG_FAIR_GROUP_SCHED is enabled.

Reduce the frequency of these calls by copying the behavior from the SMP
case, i.e. Only call util handlers for the top level cfs_rq.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: linaro-kernel@...ts.linaro.org
Fixes: 536bd00cdbb7 ("sched/fair: Fix !CONFIG_SMP kernel cpufreq governor breakage")
Link: http://lkml.kernel.org/r/6abf69a2107525885b616a2c1ec03d9c0946171c.1495603536.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 48 ++++++++++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c95880e..139abf2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2790,6 +2790,29 @@ static inline void update_cfs_shares(struct sched_entity *se)
 }
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
+static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
+{
+	if (&this_rq()->cfs == cfs_rq) {
+		/*
+		 * There are a few boundary cases this might miss but it should
+		 * get called often enough that that should (hopefully) not be
+		 * a real problem -- added to that it only calls on the local
+		 * CPU, so if we enqueue remotely we'll miss an update, but
+		 * the next tick/schedule should update.
+		 *
+		 * It will not get called when we go idle, because the idle
+		 * thread is a different class (!fair), nor will the utilization
+		 * number include things like RT tasks.
+		 *
+		 * As is, the util number is not freq-invariant (we'd have to
+		 * implement arch_scale_freq_capacity() for that).
+		 *
+		 * See cpu_util().
+		 */
+		cpufreq_update_util(rq_of(cfs_rq), 0);
+	}
+}
+
 #ifdef CONFIG_SMP
 /*
  * Approximate:
@@ -3276,29 +3299,6 @@ static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq) {}
 
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
-static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
-{
-	if (&this_rq()->cfs == cfs_rq) {
-		/*
-		 * There are a few boundary cases this might miss but it should
-		 * get called often enough that that should (hopefully) not be
-		 * a real problem -- added to that it only calls on the local
-		 * CPU, so if we enqueue remotely we'll miss an update, but
-		 * the next tick/schedule should update.
-		 *
-		 * It will not get called when we go idle, because the idle
-		 * thread is a different class (!fair), nor will the utilization
-		 * number include things like RT tasks.
-		 *
-		 * As is, the util number is not freq-invariant (we'd have to
-		 * implement arch_scale_freq_capacity() for that).
-		 *
-		 * See cpu_util().
-		 */
-		cpufreq_update_util(rq_of(cfs_rq), 0);
-	}
-}
-
 /*
  * Unsigned subtract and clamp on underflow.
  *
@@ -3544,7 +3544,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
 
 static inline void update_load_avg(struct sched_entity *se, int not_used1)
 {
-	cpufreq_update_util(rq_of(cfs_rq_of(se)), 0);
+	cfs_rq_util_change(cfs_rq_of(se));
 }
 
 static inline void