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Power management fix for v4.15-rc6

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This fixes a schedutil cpufreq governor regression from the 4.14
 cycle that may cause a CPU idleness check to return incorrect results
 in some cases which leads to suboptimal decisions (Joel Fernandes).
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Merge tag 'pm-4.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fix from Rafael Wysocki:
 "This fixes a schedutil cpufreq governor regression from the 4.14 cycle
  that may cause a CPU idleness check to return incorrect results in
  some cases which leads to suboptimal decisions (Joel Fernandes)"

* tag 'pm-4.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq: schedutil: Use idle_calls counter of the remote CPU
This commit is contained in:
Linus Torvalds 2017-12-29 11:54:15 -08:00
commit 61233580f1
3 changed files with 15 additions and 1 deletions
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1
include/linux/tick.h
View file

@ -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 */

2
kernel/sched/cpufreq_schedutil.c
View file

@ -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;

13
kernel/time/tick-sched.c
View file

@ -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
*