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cpuidle: menu: Refine idle state selection for running tick

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If the tick isn't stopped, the target residency of the state selected
by the menu governor may be greater than the actual time to the next
tick and that means lost energy.

To avoid that, make tick_nohz_get_sleep_length() return the current
time to the next event (before stopping the tick) in addition to the
estimated one via an extra pointer argument and make menu_select()
use that value to refine the state selection when necessary.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
Rafael J. Wysocki
2018-04-05 19:12:34 +02:00
parent 554c8aa8ec
commit 296bb1e51a
3 changed files with 35 additions and 11 deletions
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7
include/linux/tick.h
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@@ -122,7 +122,7 @@ extern void tick_nohz_idle_enter(void);
extern void tick_nohz_idle_exit(void);
extern void tick_nohz_irq_exit(void);
extern bool tick_nohz_idle_got_tick(void);
extern ktime_t tick_nohz_get_sleep_length(void);
extern ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next);
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);
@@ -146,9 +146,10 @@ static inline void tick_nohz_idle_enter(void) { }
static inline void tick_nohz_idle_exit(void) { }
static inline bool tick_nohz_idle_got_tick(void) { return false; }
static inline ktime_t tick_nohz_get_sleep_length(void)
static inline ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
{
return NSEC_PER_SEC / HZ;
*delta_next = TICK_NSEC;
return *delta_next;
}
static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }
static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }