[PATCH RESEND] cpufreq: schedutil: Use idle_calls counter of the remote CPU

* [PATCH RESEND] cpufreq: schedutil: Use idle_calls counter of the remote CPU
@ 2017-12-19 17:47 Joel Fernandes
  2017-12-19 18:48 ` Peter Zijlstra
  0 siblings, 1 reply; 5+ messages in thread
From: Joel Fernandes @ 2017-12-19 17:47 UTC (permalink / raw)
  To: linux-kernel
  Cc: Joel Fernandes, Srinivas Pandruvada, Len Brown,
	Rafael J. Wysocki, Viresh Kumar, Ingo Molnar, Peter Zijlstra,
	Juri Lelli, Patrick Bellasi, Chris Redpath, Steve Muckle,
	Dietmar Eggemann, Vincent Guittot, Morten Ramussen,
	Frederic Weisbecker, Thomas Gleixner, Saravana Kannan,
	Vikram Mulukutla, Rohit Jain, Atish Patra, Josef Bacik,
	Rik van Riel, EAS Dev

Since the recent remote cpufreq callback work, its possible that a cpufreq
update is triggered from a remote CPU. For single policies however, the current
code uses the local CPU when trying to determine if the remote sg_cpu entered
idle or is busy. This is incorrect. To remedy this, compare with the nohz tick
idle_calls counter of the remote CPU.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Joel Fernandes <joelaf@google.com>
---
Just resending this which is cpufreq-related as requested by Rafael rebased
on linus/master.

The other 2 patches in my last series which can go in independent of this one are:
https://patchwork.kernel.org/patch/10115395/
https://patchwork.kernel.org/patch/10115401/
I'm still waiting on scheduler maintainers to comment on those. Unfortunately,
I haven't heard back anything yet since the last repost of those.

 include/linux/tick.h             |  1 +
 kernel/sched/cpufreq_schedutil.c |  2 +-
 kernel/time/tick-sched.c         | 13 +++++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index f442d1a42025..7cc35921218e 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -119,6 +119,7 @@ extern void tick_nohz_idle_exit(void);
 extern void tick_nohz_irq_exit(void);
 extern ktime_t tick_nohz_get_sleep_length(void);
 extern unsigned long tick_nohz_get_idle_calls(void);
+extern unsigned long tick_nohz_get_idle_calls_cpu(int cpu);
 extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
 extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
 #else /* !CONFIG_NO_HZ_COMMON */
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 2f52ec0f1539..d6717a3331a1 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -244,7 +244,7 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
 #ifdef CONFIG_NO_HZ_COMMON
 static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
 {
-	unsigned long idle_calls = tick_nohz_get_idle_calls();
+	unsigned long idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
 	bool ret = idle_calls == sg_cpu->saved_idle_calls;
 
 	sg_cpu->saved_idle_calls = idle_calls;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 99578f06c8d4..77555faf6fbc 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -985,6 +985,19 @@ ktime_t tick_nohz_get_sleep_length(void)
 	return ts->sleep_length;
 }
 
+/**
+ * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
+ * for a particular CPU.
+ *
+ * Called from the schedutil frequency scaling governor in scheduler context.
+ */
+unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
+{
+	struct tick_sched *ts = tick_get_tick_sched(cpu);
+
+	return ts->idle_calls;
+}
+
 /**
  * tick_nohz_get_idle_calls - return the current idle calls counter value
  *
-- 
2.15.1.504.g5279b80103-goog

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