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

Message ID 20191116131613.15733-1-daniel.lezcano@linaro.org
State New
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Series
  • [V2,1/2] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns
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Commit Message

Daniel Lezcano Nov. 16, 2019, 1:16 p.m.
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(-)

-- 
2.17.1

Comments

Rafael J. Wysocki Nov. 20, 2019, 11:05 a.m. | #1
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!
Daniel Lezcano Nov. 20, 2019, 11:32 a.m. | #2
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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Patch

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)
 {