[PATCH V2 1/2] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns

[PATCH V2 1/2] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns

[Daniel Lezcano]

We want to specify a latency constraint when choosing an idle state at
play_idle time. Instead of duplicating the information in the
structure or propagate the latency in the call stack, change the
use_deepest_state by forced_latency_limit_ns to introduce this
constraint. The idea being that when it is set, idle is forced
(i.e. no governors), but there is a latency limit for the state to
use.

A zero latency constraint means "do not use the deepest idle state
path" as the 'use_deepest_state' boolean was used in the
cpuidle_idle_call.

In addition add the play_idle_precise() function getting a nanosec
base latency constraint as parameter. The play_idle() function becomes
a wrapper passing an U64_MAX to play_idle_precise().

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/cpuidle/cpuidle.c | 10 +++++-----
 include/linux/cpu.h       |  6 +++++-
 include/linux/cpuidle.h   |  6 +++---
 kernel/sched/idle.c       | 14 +++++++-------
 4 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 44ae39f2b47a..62226fadc02d 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -100,19 +100,19 @@ static int find_deepest_state(struct cpuidle_driver *drv,
 
 /**
  * cpuidle_use_deepest_state - Set/clear governor override flag.
- * @enable: New value of the flag.
+ * @latency_limit_ns: A latency limit constraint
  *
- * Set/unset the current CPU to use the deepest idle state (override governors
- * going forward if set).
+ * Set/unset the current CPU to use the deepest idle state with the exit
+ * latency within @latency_limit_ns
  */
-void cpuidle_use_deepest_state(bool enable)
+void cpuidle_use_deepest_state(u64 latency_limit_ns)
 {
 	struct cpuidle_device *dev;
 
 	preempt_disable();
 	dev = cpuidle_get_device();
 	if (dev)
-		dev->use_deepest_state = enable;
+		dev->forced_idle_latency_limit_ns = latency_limit_ns;
 	preempt_enable();
 }
 
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index d0633ebdaa9c..4c9694e209a5 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -179,7 +179,11 @@ void arch_cpu_idle_dead(void);
 int cpu_report_state(int cpu);
 int cpu_check_up_prepare(int cpu);
 void cpu_set_state_online(int cpu);
-void play_idle(unsigned long duration_us);
+void play_idle_precise(u64 duration_ns, u64 latency_ns);
+static inline void play_idle(unsigned long duration_us)
+{
+	play_idle_precise(duration_us * NSEC_PER_USEC, U64_MAX);
+}
 
 #ifdef CONFIG_HOTPLUG_CPU
 bool cpu_wait_death(unsigned int cpu, int seconds);
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index d23a3b1ddcf6..1f3f4dd01e48 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -83,7 +83,6 @@ struct cpuidle_driver_kobj;
 struct cpuidle_device {
 	unsigned int		registered:1;
 	unsigned int		enabled:1;
-	unsigned int		use_deepest_state:1;
 	unsigned int		poll_time_limit:1;
 	unsigned int		cpu;
 	ktime_t			next_hrtimer;
@@ -91,6 +90,7 @@ struct cpuidle_device {
 	int			last_state_idx;
 	int			last_residency;
 	u64			poll_limit_ns;
+	u64			forced_idle_latency_limit_ns;
 	struct cpuidle_state_usage	states_usage[CPUIDLE_STATE_MAX];
 	struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
 	struct cpuidle_driver_kobj *kobj_driver;
@@ -210,7 +210,7 @@ extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 				      struct cpuidle_device *dev);
 extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev);
-extern void cpuidle_use_deepest_state(bool enable);
+extern void cpuidle_use_deepest_state(u64 latency_limit_ns);
 #else
 static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 					     struct cpuidle_device *dev)
@@ -218,7 +218,7 @@ static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				       struct cpuidle_device *dev)
 {return -ENODEV; }
-static inline void cpuidle_use_deepest_state(bool enable)
+static inline void cpuidle_use_deepest_state(u64 latency_limit_ns)
 {
 }
 #endif
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 8dad5aa600ea..0a817e907192 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -165,7 +165,7 @@ static void cpuidle_idle_call(void)
 	 * until a proper wakeup interrupt happens.
 	 */
 
-	if (idle_should_enter_s2idle() || dev->use_deepest_state) {
+	if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
 		if (idle_should_enter_s2idle()) {
 			rcu_idle_enter();
 
@@ -311,7 +311,7 @@ static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
-void play_idle(unsigned long duration_us)
+void play_idle_precise(u64 duration_ns, u64 latency_ns)
 {
 	struct idle_timer it;
 
@@ -323,29 +323,29 @@ void play_idle(unsigned long duration_us)
 	WARN_ON_ONCE(current->nr_cpus_allowed != 1);
 	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
 	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
-	WARN_ON_ONCE(!duration_us);
+	WARN_ON_ONCE(!duration_ns);
 
 	rcu_sleep_check();
 	preempt_disable();
 	current->flags |= PF_IDLE;
-	cpuidle_use_deepest_state(true);
+	cpuidle_use_deepest_state(latency_ns);
 
 	it.done = 0;
 	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	it.timer.function = idle_inject_timer_fn;
-	hrtimer_start(&it.timer, ns_to_ktime(duration_us * NSEC_PER_USEC),
+	hrtimer_start(&it.timer, ns_to_ktime(duration_ns),
 		      HRTIMER_MODE_REL_PINNED);
 
 	while (!READ_ONCE(it.done))
 		do_idle();
 
-	cpuidle_use_deepest_state(false);
+	cpuidle_use_deepest_state(0);
 	current->flags &= ~PF_IDLE;
 
 	preempt_fold_need_resched();
 	preempt_enable();
 }
-EXPORT_SYMBOL_GPL(play_idle);
+EXPORT_SYMBOL_GPL(play_idle_precise);
 
 void cpu_startup_entry(enum cpuhp_state state)
 {
-- 
2.17.1

[PATCH V2 2/2] cpuidle: Use the latency to call find_deepest_idle_state

[Daniel Lezcano]

As the dev->forced_idle_latency_limit_ns is filled with the latency
value when this function is called, use it as a parameter to the
find_deepest_idle_state() function.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/cpuidle/cpuidle.c | 7 +++++--
 include/linux/cpuidle.h   | 6 ++++--
 kernel/sched/idle.c       | 8 +++++++-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 62226fadc02d..a02b701fc289 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -122,9 +122,12 @@ void cpuidle_use_deepest_state(u64 latency_limit_ns)
  * @dev: cpuidle device for the given CPU.
  */
 int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-			       struct cpuidle_device *dev)
+			       struct cpuidle_device *dev,
+			       u64 latency_limit_ns)
 {
-	return find_deepest_state(drv, dev, UINT_MAX, 0, false);
+	return find_deepest_state(drv, dev,
+				  div_u64(latency_limit_ns, NSEC_PER_USEC),
+				  0, false);
 }
 
 #ifdef CONFIG_SUSPEND
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 1f3f4dd01e48..b60f35b7d53e 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -207,13 +207,15 @@ static inline struct cpuidle_device *cpuidle_get_device(void) {return NULL; }
 
 #ifdef CONFIG_CPU_IDLE
 extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-				      struct cpuidle_device *dev);
+				      struct cpuidle_device *dev,
+				      u64 latency_limit_ns);
 extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev);
 extern void cpuidle_use_deepest_state(u64 latency_limit_ns);
 #else
 static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-					     struct cpuidle_device *dev)
+					     struct cpuidle_device *dev,
+					     u64 latency_limit_ns)
 {return -ENODEV; }
 static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				       struct cpuidle_device *dev)
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 0a817e907192..fd4a8747e602 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -166,6 +166,9 @@ static void cpuidle_idle_call(void)
 	 */
 
 	if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
+
+		u64 latency_limit_ns = dev->forced_idle_latency_limit_ns;
+
 		if (idle_should_enter_s2idle()) {
 			rcu_idle_enter();
 
@@ -176,12 +179,15 @@ static void cpuidle_idle_call(void)
 			}
 
 			rcu_idle_exit();
+
+			latency_limit_ns = U64_MAX;
 		}
 
 		tick_nohz_idle_stop_tick();
 		rcu_idle_enter();
 
-		next_state = cpuidle_find_deepest_state(drv, dev);
+		next_state = cpuidle_find_deepest_state(drv, dev,
+							latency_limit_ns);
 		call_cpuidle(drv, dev, next_state);
 	} else {
 		bool stop_tick = true;
-- 
2.17.1

Re: [PATCH V2 1/2] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns

[Rafael J. Wysocki]

On Saturday, November 16, 2019 2:16:12 PM CET Daniel Lezcano wrote:
> We want to specify a latency constraint when choosing an idle state at
> play_idle time. Instead of duplicating the information in the
> structure or propagate the latency in the call stack, change the
> use_deepest_state by forced_latency_limit_ns to introduce this
> constraint. The idea being that when it is set, idle is forced
> (i.e. no governors), but there is a latency limit for the state to
> use.
> 
> A zero latency constraint means "do not use the deepest idle state
> path" as the 'use_deepest_state' boolean was used in the
> cpuidle_idle_call.
> 
> In addition add the play_idle_precise() function getting a nanosec
> base latency constraint as parameter. The play_idle() function becomes
> a wrapper passing an U64_MAX to play_idle_precise().
> 
> Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>  drivers/cpuidle/cpuidle.c | 10 +++++-----
>  include/linux/cpu.h       |  6 +++++-
>  include/linux/cpuidle.h   |  6 +++---
>  kernel/sched/idle.c       | 14 +++++++-------
>  4 files changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 44ae39f2b47a..62226fadc02d 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -100,19 +100,19 @@ static int find_deepest_state(struct cpuidle_driver *drv,
>  
>  /**
>   * cpuidle_use_deepest_state - Set/clear governor override flag.
> - * @enable: New value of the flag.
> + * @latency_limit_ns: A latency limit constraint
>   *
> - * Set/unset the current CPU to use the deepest idle state (override governors
> - * going forward if set).
> + * Set/unset the current CPU to use the deepest idle state with the exit
> + * latency within @latency_limit_ns
>   */
> -void cpuidle_use_deepest_state(bool enable)
> +void cpuidle_use_deepest_state(u64 latency_limit_ns)
>  {
>  	struct cpuidle_device *dev;
>  
>  	preempt_disable();
>  	dev = cpuidle_get_device();
>  	if (dev)
> -		dev->use_deepest_state = enable;
> +		dev->forced_idle_latency_limit_ns = latency_limit_ns;
>  	preempt_enable();
>  }
>  
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index d0633ebdaa9c..4c9694e209a5 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -179,7 +179,11 @@ void arch_cpu_idle_dead(void);
>  int cpu_report_state(int cpu);
>  int cpu_check_up_prepare(int cpu);
>  void cpu_set_state_online(int cpu);
> -void play_idle(unsigned long duration_us);
> +void play_idle_precise(u64 duration_ns, u64 latency_ns);
> +static inline void play_idle(unsigned long duration_us)
> +{
> +	play_idle_precise(duration_us * NSEC_PER_USEC, U64_MAX);
> +}
>  
>  #ifdef CONFIG_HOTPLUG_CPU
>  bool cpu_wait_death(unsigned int cpu, int seconds);
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index d23a3b1ddcf6..1f3f4dd01e48 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -83,7 +83,6 @@ struct cpuidle_driver_kobj;
>  struct cpuidle_device {
>  	unsigned int		registered:1;
>  	unsigned int		enabled:1;
> -	unsigned int		use_deepest_state:1;
>  	unsigned int		poll_time_limit:1;
>  	unsigned int		cpu;
>  	ktime_t			next_hrtimer;
> @@ -91,6 +90,7 @@ struct cpuidle_device {
>  	int			last_state_idx;
>  	int			last_residency;
>  	u64			poll_limit_ns;
> +	u64			forced_idle_latency_limit_ns;
>  	struct cpuidle_state_usage	states_usage[CPUIDLE_STATE_MAX];
>  	struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
>  	struct cpuidle_driver_kobj *kobj_driver;
> @@ -210,7 +210,7 @@ extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>  				      struct cpuidle_device *dev);
>  extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
>  				struct cpuidle_device *dev);
> -extern void cpuidle_use_deepest_state(bool enable);
> +extern void cpuidle_use_deepest_state(u64 latency_limit_ns);
>  #else
>  static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>  					     struct cpuidle_device *dev)
> @@ -218,7 +218,7 @@ static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>  static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
>  				       struct cpuidle_device *dev)
>  {return -ENODEV; }
> -static inline void cpuidle_use_deepest_state(bool enable)
> +static inline void cpuidle_use_deepest_state(u64 latency_limit_ns)
>  {
>  }
>  #endif
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 8dad5aa600ea..0a817e907192 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -165,7 +165,7 @@ static void cpuidle_idle_call(void)
>  	 * until a proper wakeup interrupt happens.
>  	 */
>  
> -	if (idle_should_enter_s2idle() || dev->use_deepest_state) {
> +	if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
>  		if (idle_should_enter_s2idle()) {
>  			rcu_idle_enter();
>  
> @@ -311,7 +311,7 @@ static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
>  	return HRTIMER_NORESTART;
>  }
>  
> -void play_idle(unsigned long duration_us)
> +void play_idle_precise(u64 duration_ns, u64 latency_ns)
>  {
>  	struct idle_timer it;
>  
> @@ -323,29 +323,29 @@ void play_idle(unsigned long duration_us)
>  	WARN_ON_ONCE(current->nr_cpus_allowed != 1);
>  	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
>  	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
> -	WARN_ON_ONCE(!duration_us);
> +	WARN_ON_ONCE(!duration_ns);
>  
>  	rcu_sleep_check();
>  	preempt_disable();
>  	current->flags |= PF_IDLE;
> -	cpuidle_use_deepest_state(true);
> +	cpuidle_use_deepest_state(latency_ns);
>  
>  	it.done = 0;
>  	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
>  	it.timer.function = idle_inject_timer_fn;
> -	hrtimer_start(&it.timer, ns_to_ktime(duration_us * NSEC_PER_USEC),
> +	hrtimer_start(&it.timer, ns_to_ktime(duration_ns),
>  		      HRTIMER_MODE_REL_PINNED);
>  
>  	while (!READ_ONCE(it.done))
>  		do_idle();
>  
> -	cpuidle_use_deepest_state(false);
> +	cpuidle_use_deepest_state(0);
>  	current->flags &= ~PF_IDLE;
>  
>  	preempt_fold_need_resched();
>  	preempt_enable();
>  }
> -EXPORT_SYMBOL_GPL(play_idle);
> +EXPORT_SYMBOL_GPL(play_idle_precise);
>  
>  void cpu_startup_entry(enum cpuhp_state state)
>  {
> 

Queued up for 5.5 along with the [2/2], but I have made quite a few changes
to the patches, so please double check the result in my bleeding-edge branch.

Thanks!

Re: [PATCH V2 1/2] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns

[Daniel Lezcano]

On 20/11/2019 12:05, Rafael J. Wysocki wrote:
> On Saturday, November 16, 2019 2:16:12 PM CET Daniel Lezcano wrote:
>> We want to specify a latency constraint when choosing an idle state at
>> play_idle time. Instead of duplicating the information in the
>> structure or propagate the latency in the call stack, change the
>> use_deepest_state by forced_latency_limit_ns to introduce this
>> constraint. The idea being that when it is set, idle is forced
>> (i.e. no governors), but there is a latency limit for the state to
>> use.
>>
>> A zero latency constraint means "do not use the deepest idle state
>> path" as the 'use_deepest_state' boolean was used in the
>> cpuidle_idle_call.
>>
>> In addition add the play_idle_precise() function getting a nanosec
>> base latency constraint as parameter. The play_idle() function becomes
>> a wrapper passing an U64_MAX to play_idle_precise().
>>
>> Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>> ---

[ ... ]

> Queued up for 5.5 along with the [2/2], but I have made quite a few changes
> to the patches, so please double check the result in my bleeding-edge branch.
> 
> Thanks!

They look good to me.

Thanks

  -- Daniel


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