[PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Len Brown]

From: Len Brown <len.brown@intel.com>

While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
cpuidle to shallow idle states, there is no simple mechanism
to give the hardware permission to enter the deeptest state permitted by PM_QOS.

Here we create the "cpuidle.use_deepest" modparam to provide this capability.

"cpuidle.use_deepest=Y" can be set at boot-time, and
/sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.

n.b.

Within the constraints of PM_QOS, this mechanism gives the hardware
permission to choose the deeptest power savings and highest latency
state available.  And so choice will depend on the particular hardware.

Also, if PM_QOS is not informed of latency constraints, it can't help.
In that case, using this mechanism may result in entering high-latency
states that impact performance.

Signed-off-by: Len Brown <len.brown@intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  4 ++++
 drivers/cpuidle/cpuidle.c                       | 19 ++++++++++++++++
 include/linux/cpuidle.h                         |  7 ++++++
 kernel/sched/idle.c                             | 30 +++++++++++++++++++------
 4 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 05496622b4ef..20f70de688bf 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -659,6 +659,10 @@
 	cpuidle.off=1	[CPU_IDLE]
 			disable the cpuidle sub-system
 
+	cpuidle.use_deepest=Y	[CPU_IDLE]
+			Ignore cpuidle governor, always choose deepest
+			PM_QOS-legal CPU idle power saving state.
+
 	cpufreq.off=1	[CPU_FREQ]
 			disable the cpufreq sub-system
 
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 484cc8909d5c..afee5aab7719 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -34,6 +34,7 @@ LIST_HEAD(cpuidle_detected_devices);
 
 static int enabled_devices;
 static int off __read_mostly;
+static bool use_deepest __read_mostly;
 static int initialized __read_mostly;
 
 int cpuidle_disabled(void)
@@ -116,6 +117,10 @@ void cpuidle_use_deepest_state(bool enable)
 	preempt_enable();
 }
 
+bool cpuidle_using_deepest_state(void)
+{
+	return use_deepest;
+}
 /**
  * cpuidle_find_deepest_state - Find the deepest available idle state.
  * @drv: cpuidle driver for the given CPU.
@@ -127,6 +132,19 @@ int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 	return find_deepest_state(drv, dev, UINT_MAX, 0, false);
 }
 
+/**
+ * cpuidle_find_deepest_state_qos - Find the deepest available idle state.
+ * @drv: cpuidle driver for the given CPU.
+ * @dev: cpuidle device for the given CPU.
+ * Honors PM_QOS
+ */
+int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
+			       struct cpuidle_device *dev)
+{
+	return find_deepest_state(drv, dev,
+			pm_qos_request(PM_QOS_CPU_DMA_LATENCY), 0, false);
+}
+
 #ifdef CONFIG_SUSPEND
 static void enter_s2idle_proper(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev, int index)
@@ -681,4 +699,5 @@ static int __init cpuidle_init(void)
 }
 
 module_param(off, int, 0444);
+module_param(use_deepest, bool, 0644);
 core_initcall(cpuidle_init);
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 8f7788d23b57..e3c2c9d1898f 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -198,19 +198,26 @@ 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);
+extern int cpuidle_find_deepest_state_qos(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 bool cpuidle_using_deepest_state(void);
 #else
 static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 					     struct cpuidle_device *dev)
 {return -ENODEV; }
+static inline int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
+					     struct cpuidle_device *dev)
+{return -ENODEV; }
 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 bool cpuidle_using_deepest_state(void) {return false; }
 #endif
 
 /* kernel/sched/idle.c */
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 257f4f0b4532..6c7348ae28ec 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -167,17 +167,33 @@ 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()) {
-			entered_state = cpuidle_enter_s2idle(drv, dev);
-			if (entered_state > 0) {
-				local_irq_enable();
-				goto exit_idle;
-			}
+	if (idle_should_enter_s2idle()) {
+		entered_state = cpuidle_enter_s2idle(drv, dev);
+		if (entered_state > 0) {
+			local_irq_enable();
+			goto exit_idle;
 		}
+	}
 
+	/*
+	 * cpuidle_dev->user_deepest_state is per-device, and thus per-CPU.
+	 * it is used to force power-savings, and thus does not obey PM_QOS.
+	 */
+
+	if (dev->use_deepest_state) {
 		next_state = cpuidle_find_deepest_state(drv, dev);
 		call_cpuidle(drv, dev, next_state);
+	}
+
+	/*
+	 * cpuidle_using_deepest_state() is system-wide, applying to all CPUs.
+	 * When activated, Linux gives the hardware permission to go as deep
+	 * as PM_QOS allows.
+	 */
+
+	else if (cpuidle_using_deepest_state()) {
+		next_state = cpuidle_find_deepest_state_qos(drv, dev);
+		call_cpuidle(drv, dev, next_state);
 	} else {
 		/*
 		 * Ask the cpuidle framework to choose a convenient idle state.
-- 
2.14.0-rc0

Re: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Vincent Guittot]

Hi Len

On 9 November 2017 at 08:38, Len Brown <lenb@kernel.org> wrote:
> From: Len Brown <len.brown@intel.com>
>
> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
> cpuidle to shallow idle states, there is no simple mechanism
> to give the hardware permission to enter the deeptest state permitted by PM_QOS.

and by per device resume latency QoS

>
> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>
> "cpuidle.use_deepest=Y" can be set at boot-time, and
> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.
>
> n.b.
>
> Within the constraints of PM_QOS, this mechanism gives the hardware
> permission to choose the deeptest power savings and highest latency
> state available.  And so choice will depend on the particular hardware.
>
> Also, if PM_QOS is not informed of latency constraints, it can't help.
> In that case, using this mechanism may result in entering high-latency
> states that impact performance.
>
> Signed-off-by: Len Brown <len.brown@intel.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  4 ++++
>  drivers/cpuidle/cpuidle.c                       | 19 ++++++++++++++++
>  include/linux/cpuidle.h                         |  7 ++++++
>  kernel/sched/idle.c                             | 30 +++++++++++++++++++------
>  4 files changed, 53 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 05496622b4ef..20f70de688bf 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -659,6 +659,10 @@
>         cpuidle.off=1   [CPU_IDLE]
>                         disable the cpuidle sub-system
>
> +       cpuidle.use_deepest=Y   [CPU_IDLE]
> +                       Ignore cpuidle governor, always choose deepest
> +                       PM_QOS-legal CPU idle power saving state.
> +
>         cpufreq.off=1   [CPU_FREQ]
>                         disable the cpufreq sub-system
>
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 484cc8909d5c..afee5aab7719 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -34,6 +34,7 @@ LIST_HEAD(cpuidle_detected_devices);
>
>  static int enabled_devices;
>  static int off __read_mostly;
> +static bool use_deepest __read_mostly;
>  static int initialized __read_mostly;
>
>  int cpuidle_disabled(void)
> @@ -116,6 +117,10 @@ void cpuidle_use_deepest_state(bool enable)
>         preempt_enable();
>  }
>
> +bool cpuidle_using_deepest_state(void)
> +{
> +       return use_deepest;
> +}
>  /**
>   * cpuidle_find_deepest_state - Find the deepest available idle state.
>   * @drv: cpuidle driver for the given CPU.
> @@ -127,6 +132,19 @@ int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>         return find_deepest_state(drv, dev, UINT_MAX, 0, false);
>  }
>
> +/**
> + * cpuidle_find_deepest_state_qos - Find the deepest available idle state.
> + * @drv: cpuidle driver for the given CPU.
> + * @dev: cpuidle device for the given CPU.
> + * Honors PM_QOS
> + */
> +int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
> +                              struct cpuidle_device *dev)
> +{
> +       return find_deepest_state(drv, dev,
> +                       pm_qos_request(PM_QOS_CPU_DMA_LATENCY), 0, false);

You should also take into account per device latency  like in menu governor:
dev_pm_qos_raw_read_value(device);


> +}
> +
>  #ifdef CONFIG_SUSPEND
>  static void enter_s2idle_proper(struct cpuidle_driver *drv,
>                                 struct cpuidle_device *dev, int index)
> @@ -681,4 +699,5 @@ static int __init cpuidle_init(void)
>  }
>
>  module_param(off, int, 0444);
> +module_param(use_deepest, bool, 0644);
>  core_initcall(cpuidle_init);
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 8f7788d23b57..e3c2c9d1898f 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -198,19 +198,26 @@ 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);
> +extern int cpuidle_find_deepest_state_qos(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 bool cpuidle_using_deepest_state(void);
>  #else
>  static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>                                              struct cpuidle_device *dev)
>  {return -ENODEV; }
> +static inline int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
> +                                            struct cpuidle_device *dev)
> +{return -ENODEV; }
>  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 bool cpuidle_using_deepest_state(void) {return false; }
>  #endif
>
>  /* kernel/sched/idle.c */
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 257f4f0b4532..6c7348ae28ec 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -167,17 +167,33 @@ 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()) {
> -                       entered_state = cpuidle_enter_s2idle(drv, dev);
> -                       if (entered_state > 0) {
> -                               local_irq_enable();
> -                               goto exit_idle;
> -                       }
> +       if (idle_should_enter_s2idle()) {
> +               entered_state = cpuidle_enter_s2idle(drv, dev);
> +               if (entered_state > 0) {
> +                       local_irq_enable();
> +                       goto exit_idle;
>                 }
> +       }
>
> +       /*
> +        * cpuidle_dev->user_deepest_state is per-device, and thus per-CPU.
> +        * it is used to force power-savings, and thus does not obey PM_QOS.
> +        */
> +
> +       if (dev->use_deepest_state) {
>                 next_state = cpuidle_find_deepest_state(drv, dev);
>                 call_cpuidle(drv, dev, next_state);
> +       }
> +
> +       /*
> +        * cpuidle_using_deepest_state() is system-wide, applying to all CPUs.
> +        * When activated, Linux gives the hardware permission to go as deep
> +        * as PM_QOS allows.
> +        */
> +
> +       else if (cpuidle_using_deepest_state()) {
> +               next_state = cpuidle_find_deepest_state_qos(drv, dev);
> +               call_cpuidle(drv, dev, next_state);
>         } else {
>                 /*
>                  * Ask the cpuidle framework to choose a convenient idle state.
> --
> 2.14.0-rc0
>

Re: cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Ramesh Thomas]

On 2017-11-09 at 02:38:51 -0500, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
> 

[cut]

> +/**
> + * cpuidle_find_deepest_state_qos - Find the deepest available idle state.
> + * @drv: cpuidle driver for the given CPU.
> + * @dev: cpuidle device for the given CPU.
> + * Honors PM_QOS
> + */
> +int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
> +			       struct cpuidle_device *dev)
> +{
> +	return find_deepest_state(drv, dev,
> +			pm_qos_request(PM_QOS_CPU_DMA_LATENCY), 0, false);

I think here the per-cpu PM QoS latency requirement should also be considered.  
User would have kept the system wide PM QoS at default high and set a low       
latency tolerance for a CPU.                                                    
                                                                                
Like it is done in the menu cpuidle governor -                                  
                                                                                
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);                       
struct device *device = get_cpu_device(dev->cpu);                               
int resume_latency = dev_pm_qos_raw_read_value(device);                         
                                                                                
Then take the lower of the 2.                                                   
        if (resume_latency && resume_latency < latency_req)                     
                                latency_req = resume_latency;                   

> +}
> +
>  #ifdef CONFIG_SUSPEND
>  static void enter_s2idle_proper(struct cpuidle_driver *drv,
>  				struct cpuidle_device *dev, int index)
> @@ -681,4 +699,5 @@ static int __init cpuidle_init(void)
>  }
>  
>  module_param(off, int, 0444);
> +module_param(use_deepest, bool, 0644);
>  core_initcall(cpuidle_init);
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 8f7788d23b57..e3c2c9d1898f 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -198,19 +198,26 @@ 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);
> +extern int cpuidle_find_deepest_state_qos(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 bool cpuidle_using_deepest_state(void);
>  #else
>  static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
>  					     struct cpuidle_device *dev)
>  {return -ENODEV; }
> +static inline int cpuidle_find_deepest_state_qos(struct cpuidle_driver *drv,
> +					     struct cpuidle_device *dev)
> +{return -ENODEV; }
>  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 bool cpuidle_using_deepest_state(void) {return false; }
>  #endif
>  
>  /* kernel/sched/idle.c */
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 257f4f0b4532..6c7348ae28ec 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -167,17 +167,33 @@ 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()) {
> -			entered_state = cpuidle_enter_s2idle(drv, dev);
> -			if (entered_state > 0) {
> -				local_irq_enable();
> -				goto exit_idle;
> -			}
> +	if (idle_should_enter_s2idle()) {
> +		entered_state = cpuidle_enter_s2idle(drv, dev);
> +		if (entered_state > 0) {
> +			local_irq_enable();
> +			goto exit_idle;
>  		}

Looks like there is a change in behavior here. Earlier if entered_state is <= 0 
then it finds the deepest state and enters it. Now it will go through the       
checks below and may even end up calling the governor, which it should not
based on the comment about s2idle above this if block.
                                                                                
> +	}
>  
> +	/*
> +	 * cpuidle_dev->user_deepest_state is per-device, and thus per-CPU.
> +	 * it is used to force power-savings, and thus does not obey PM_QOS.
> +	 */
> +
> +	if (dev->use_deepest_state) {
>  		next_state = cpuidle_find_deepest_state(drv, dev);
>  		call_cpuidle(drv, dev, next_state);
> +	}
> +
> +	/*
> +	 * cpuidle_using_deepest_state() is system-wide, applying to all CPUs.
> +	 * When activated, Linux gives the hardware permission to go as deep
> +	 * as PM_QOS allows.
> +	 */
> +
> +	else if (cpuidle_using_deepest_state()) {
> +		next_state = cpuidle_find_deepest_state_qos(drv, dev);
> +		call_cpuidle(drv, dev, next_state);
>  	} else {
>  		/*
>  		 * Ask the cpuidle framework to choose a convenient idle state.


Regards,
Ramesh

Re: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Thomas Ilsche]

On 2017-11-09 08:38, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
> 
> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
> cpuidle to shallow idle states, there is no simple mechanism
> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
> 
> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
> 
> "cpuidle.use_deepest=Y" can be set at boot-time, and
> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.

This is a good option to have and can conveniently prevent idle power consumption
issues. But that wouldn't be a reasonable default, would it?
I still think there is an inherent need for a heuristic and a corresponding
mitigation to avoid staying in a sleep state too long.

Best,
Thomas

RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Doug Smythies]

On 2017.11.16 08:11 Thomas Ilsche wrote:
> On 2017-11-09 08:38, Len Brown wrote:
>> From: Len Brown <len.brown@intel.com>
>> 
>> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
>> cpuidle to shallow idle states, there is no simple mechanism
>> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
>> 
>> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>> 
>> "cpuidle.use_deepest=Y" can be set at boot-time, and
>> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.
>
> This is a good option to have and can conveniently prevent idle power consumption
> issues. But that wouldn't be a reasonable default, would it?
> I still think there is an inherent need for a heuristic and a corresponding
> mitigation to avoid staying in a sleep state too long.

I think so, yes. The potential energy savings, depending on work flow, are significant.
For the idle state 0 case, I have some supporting data that I will send on
the other e-mail thread.

... Doug

RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Doug Smythies]

On 2017.11.16 08:11 Thomas Ilsche wrote:
> On 2017-11-09 08:38, Len Brown wrote:
>> From: Len Brown <len.brown@intel.com>
>> 
>> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
>> cpuidle to shallow idle states, there is no simple mechanism
>> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
>> 
>> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>> 
>> "cpuidle.use_deepest=Y" can be set at boot-time, and
>> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.
>
> This is a good option to have and can conveniently prevent idle power consumption
> issues. But that wouldn't be a reasonable default, would it?
> I still think there is an inherent need for a heuristic and a corresponding
> mitigation to avoid staying in a sleep state too long.

I think so, yes. The potential energy savings, depending on work flow, are significant.
For the idle state 0 case, I have some supporting data that I will send on
the other e-mail thread.

... Doug

RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Doug Smythies]

Hi Len,

Other feedback notwithstanding, works fine for me.
Just a small typo type comment:

On 2017.11.08 23:39 Len Brown wrote:

...[snip]...

> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
> 
> "cpuidle.use_deepest=Y" can be set at boot-time, and
> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.

Should be:

/sys/module/cpuidle/parameters/use_deepest

...[snip]...

RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Doug Smythies]

Hi Len,

Other feedback notwithstanding, works fine for me.
Just a small typo type comment:

On 2017.11.08 23:39 Len Brown wrote:

...[snip]...

> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
> 
> "cpuidle.use_deepest=Y" can be set at boot-time, and
> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.

Should be:

/sys/module/cpuidle/parameters/use_deepest

...[snip]...