Patch "cpufreq: schedutil: Use idle_calls counter of the remote CPU" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Dec 30, 2017

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Stable branch Scheduler CPU frequency scaling framework Nohz, dynticks support

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2017-12-30 15:25 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

cpufreq: schedutil: Use idle_calls counter of the remote CPU

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cpufreq-schedutil-use-idle_calls-counter-of-the-remote-cpu.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 466a2b42d67644447a1765276259a3ea5531ddff Mon Sep 17 00:00:00 2001

From: Joel Fernandes <[email protected]>
Date: Thu, 21 Dec 2017 02:22:45 +0100
Subject: cpufreq: schedutil: Use idle_calls counter of the remote CPU

From: Joel Fernandes <[email protected]>

commit 466a2b42d67644447a1765276259a3ea5531ddff upstream.

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.

Fixes 674e75411fc2 (sched: cpufreq: Allow remote cpufreq callbacks)

Acked-by Viresh Kumar <[email protected]>

Acked-by Peter Zijlstra (Intel) <[email protected]>

Signed-off-by Joel Fernandes <[email protected]>

Signed-off-by Rafael J. Wysocki <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

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

include/linux/tick.h +1 -0

@@ -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 */

kernel/sched/cpufreq_schedutil.c +1 -1

@@ -244,7 +244,7 @@ static void sugov_iowait_boost(struct su
 #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;

kernel/time/tick-sched.c +13 -0

@@ -1010,6 +1010,19 @@ ktime_t tick_nohz_get_sleep_length(void)
 }
 
 /**
+ * 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
  *
  * Called from the schedutil frequency scaling governor in scheduler context.

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/cpufreq-schedutil-use-idle_calls-counter-of-the-remote-cpu.patch