linux-kernel - [PATCH RFC 3/5] cpufreq: schedutil: Use idle

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Date:   Sat, 28 Oct 2017 02:59:39 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Fernandes <joelaf@...gle.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Cc: Srinivas Pandruvada" <srinivas.pandruvada@...ux.intel.com>,
        "Cc: Len Brown" <lenb@...nel.org>,
        "Cc: Juri Lelli" <juri.lelli@....com>,
        "Cc: Patrick Bellasi" <patrick.bellasi@....com>,
        "Cc: Steve Muckle" <smuckle@...gle.com>,
        "Cc: Brendan Jackman" <brendan.jackman@....com>,
        "Cc: Chris Redpath" <Chris.Redpath@....com>,
        "Cc: Atish Patra" <atish.patra@...cle.com>,
        "Cc: Dietmar Eggemann" <dietmar.eggemann@....com>,
        "Cc: Vincent Guittot" <vincent.guittot@...aro.org>,
        "Cc: Morten Ramussen" <morten.rasmussen@....com>,
        "Cc: EAS Dev" <eas-dev@...ts.linaro.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>
Subject: [PATCH RFC 3/5] cpufreq: schedutil: Use idle_calls counter of the remote CPU

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.

Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Joel Fernandes <joelaf@...gle.com>
---
 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 fe01e68bf520..31bf2ae3e9a7 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -118,6 +118,7 @@ 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 9209d83ecdcf..1383aa9efb4f 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 7b258c59d78a..91d5e7be805b 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1011,6 +1011,19 @@ 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
  *
-- 
2.15.0.rc2.357.g7e34df9404-goog