linux-kernel - [tip:sched/core] sched/fair: Defer calling scaling functions

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Date:	Sun, 13 Sep 2015 04:06:17 -0700
From:	tip-bot for Dietmar Eggemann <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	daniel.lezcano@...aro.org, linux-kernel@...r.kernel.org,
	mturquette@...libre.com, mingo@...nel.org, rjw@...ysocki.net,
	sgurrappadi@...dia.com, vincent.guittot@...aro.org,
	peterz@...radead.org, Juri.Lelli@....com, pang.xunlei@....com.cn,
	efault@....de, dietmar.eggemann@....com, tglx@...utronix.de,
	yuyang.du@...el.com, torvalds@...ux-foundation.org, hpa@...or.com
Subject: [tip:sched/core] sched/fair: Defer calling scaling functions

Commit-ID:  6f2b04524f0b38bfbb8413f98d2d6af234508309
Gitweb:     http://git.kernel.org/tip/6f2b04524f0b38bfbb8413f98d2d6af234508309
Author:     Dietmar Eggemann <dietmar.eggemann@....com>
AuthorDate: Mon, 7 Sep 2015 14:57:22 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 13 Sep 2015 09:53:01 +0200

sched/fair: Defer calling scaling functions

Do not call the scaling functions in case time goes backwards or the
last update of the sched_avg structure has happened less than 1024ns
ago.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Juri Lelli <Juri.Lelli@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: daniel.lezcano@...aro.org <daniel.lezcano@...aro.org>
Cc: mturquette@...libre.com <mturquette@...libre.com>
Cc: pang.xunlei@....com.cn <pang.xunlei@....com.cn>
Cc: rjw@...ysocki.net <rjw@...ysocki.net>
Cc: sgurrappadi@...dia.com <sgurrappadi@...dia.com>
Cc: vincent.guittot@...aro.org <vincent.guittot@...aro.org>
Cc: yuyang.du@...el.com <yuyang.du@...el.com>
Link: http://lkml.kernel.org/r/55EDA2E9.8040900@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c3c5585..fc835fa 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2552,8 +2552,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
 	u64 delta, scaled_delta, periods;
 	u32 contrib;
 	unsigned int delta_w, scaled_delta_w, decayed = 0;
-	unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
-	unsigned long scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
+	unsigned long scale_freq, scale_cpu;
 
 	delta = now - sa->last_update_time;
 	/*
@@ -2574,6 +2573,9 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
 		return 0;
 	sa->last_update_time = now;
 
+	scale_freq = arch_scale_freq_capacity(NULL, cpu);
+	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
+
 	/* delta_w is the amount already accumulated against our next period */
 	delta_w = sa->period_contrib;
 	if (delta + delta_w >= 1024) {
--
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