[PATCH] sched/fair: remove #ifdefs from scale_rt_capacity

* [PATCH] sched/fair: remove #ifdefs from scale_rt_capacity
@ 2018-07-19 12:00 Vincent Guittot
  2018-07-20  4:55 ` Viresh Kumar
                   ` (2 more replies)
  0 siblings, 3 replies; 10+ messages in thread
From: Vincent Guittot @ 2018-07-19 12:00 UTC (permalink / raw)
  To: peterz, mingo, linux-kernel; +Cc: rjw, viresh.kumar, Vincent Guittot

Reuse cpu_util_irq() that has been defined for schedutil and set irq util
to 0 when !CONFIG_IRQ_TIME_ACCOUNTING

But the compiler is not able to optimize the sequence (at least with
aarch64 GCC 7.2.1)
	free *= (max - irq);
	free /= max;
when irq is fixed to 0

Add a new inline function scale_irq_capacity() that will scale utilization
when irq is accounted. Reuse this funciton in schedutil which applies
similar formula.

Suggested-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/cpufreq_schedutil.c |  3 +--
 kernel/sched/fair.c              | 13 +++----------
 kernel/sched/sched.h             | 20 ++++++++++++++++++--
 3 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 97dcd44..3fffad3 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -247,8 +247,7 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
 	 *   U' = irq + ------- * U
 	 *                max
 	 */
-	util *= (max - irq);
-	util /= max;
+	util = scale_irq_capacity(util, irq, max);
 	util += irq;
 
 	/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d5f7d52..14c3fdd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7551,16 +7551,12 @@ static unsigned long scale_rt_capacity(int cpu)
 	struct rq *rq = cpu_rq(cpu);
 	unsigned long max = arch_scale_cpu_capacity(NULL, cpu);
 	unsigned long used, free;
-#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
 	unsigned long irq;
-#endif
 
-#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
-	irq = READ_ONCE(rq->avg_irq.util_avg);
+	irq = cpu_util_irq(rq);
 
 	if (unlikely(irq >= max))
 		return 1;
-#endif
 
 	used = READ_ONCE(rq->avg_rt.util_avg);
 	used += READ_ONCE(rq->avg_dl.util_avg);
@@ -7569,11 +7565,8 @@ static unsigned long scale_rt_capacity(int cpu)
 		return 1;
 
 	free = max - used;
-#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
-	free *= (max - irq);
-	free /= max;
-#endif
-	return free;
+
+	return scale_irq_capacity(free, irq, max);
 }
 
 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ebb4b3c..b80c3fd 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2210,17 +2210,33 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
 {
 	return READ_ONCE(rq->avg_rt.util_avg);
 }
+#endif
 
-#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
+#if defined(SMP) \
+ && (defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING))
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
 	return rq->avg_irq.util_avg;
 }
+
+static inline
+unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned long max)
+{
+	util *= (max - irq);
+	util /= max;
+
+	return util;
+
+}
 #else
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
 	return 0;
 }
 
-#endif
+static inline
+unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned long max)
+{
+	return util;
+}
 #endif
-- 
2.7.4


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