[V1,1/3] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns

Message ID 20191114204914.21206-1-daniel.lezcano@linaro.org
State New
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Series
  • [V1,1/3] cpuidle: Replace use_deepest_state flag by forced_idle_latency_limit_ns
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Commit Message

Daniel Lezcano Nov. 14, 2019, 8:49 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.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

---
 drivers/cpuidle/cpuidle.c | 10 +++++-----
 include/linux/cpuidle.h   |  6 +++---
 kernel/sched/idle.c       |  6 +++---
 3 files changed, 11 insertions(+), 11 deletions(-)

-- 
2.17.1

Comments

Rafael J. Wysocki Nov. 14, 2019, 10:17 p.m. | #1
On Thu, Nov 14, 2019 at 9:49 PM Daniel Lezcano
<daniel.lezcano@linaro.org> 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.

>

> Suggested-by: Rafael J. Wysocki <rafael@kernel.org>

> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

> ---

>  drivers/cpuidle/cpuidle.c | 10 +++++-----

>  include/linux/cpuidle.h   |  6 +++---

>  kernel/sched/idle.c       |  6 +++---

>  3 files changed, 11 insertions(+), 11 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/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..d4681b3d7074 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();

>

> @@ -328,7 +328,7 @@ void play_idle(unsigned long duration_us)

>         rcu_sleep_check();

>         preempt_disable();

>         current->flags |= PF_IDLE;

> -       cpuidle_use_deepest_state(true);

> +       cpuidle_use_deepest_state(1);


This is kind of artificial without the changes in the second patch, so
I would fold the [2/3] into this one.

Apart from that the patches look reasonable to me.

>

>         it.done = 0;

>         hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

> @@ -339,7 +339,7 @@ void play_idle(unsigned long duration_us)

>         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();

> --

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/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..d4681b3d7074 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();
 
@@ -328,7 +328,7 @@  void play_idle(unsigned long duration_us)
 	rcu_sleep_check();
 	preempt_disable();
 	current->flags |= PF_IDLE;
-	cpuidle_use_deepest_state(true);
+	cpuidle_use_deepest_state(1);
 
 	it.done = 0;
 	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
@@ -339,7 +339,7 @@  void play_idle(unsigned long duration_us)
 	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();