cpuidle: remove CPUIDLE_FLAG_TIME_INVALID

cpuidle: remove CPUIDLE_FLAG_TIME_INVALID

[Len Brown]

Daniel Lezcano suggested removing CPUIDLE_FLAG_TIME_INVALID because
no states enable interrupts, and so cpuidle can always measure valid
residency time.  That turns out not to be un-true since x86 HALT is
invoked with interrupts enabled.  But looking at the code more closely,
Daniel's suggestion of simply removing the CPUIDLE_FLAG_TIME_INVALID
is actually an improvement over the workaround that we are currently using.

[PATCH 1/3] cpuidle menu: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID

[Len Brown]

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

When menu sees CPUIDLE_FLAG_TIME_INVALID, it ignores its timestamps,
and assumes that idle lasted as long as the time till next predicted
timer expiration.

But if an interrupt was seen and serviced before that duration,
it would actually be more accurate to use the measured time
rather than rounding up to the next predicted timer expiration.

And if an interrupt is seen and serviced such that the mesured time
exceeds the time till next predicted timer expiration, then
truncating to that expiration is the right thing to do --
since we can never stay idle past that timer expiration.

So the code can do a better job without
checking for CPUIDLE_FLAG_TIME_INVALID.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/cpuidle/governors/menu.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 659d7b0..4058079 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -396,8 +396,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	 * power state and occurrence of the wakeup event.
 	 *
 	 * If the entered idle state didn't support residency measurements,
-	 * we are basically lost in the dark how much time passed.
-	 * As a compromise, assume we slept for the whole expected time.
+	 * we use them anyway if they are short, and if long,
+	 * truncate to the whole expected time.
 	 *
 	 * Any measured amount of time will include the exit latency.
 	 * Since we are interested in when the wakeup begun, not when it
@@ -405,22 +405,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	 * the measured amount of time is less than the exit latency,
 	 * assume the state was never reached and the exit latency is 0.
 	 */
-	if (unlikely(target->flags & CPUIDLE_FLAG_TIME_INVALID)) {
-		/* Use timer value as is */
-		measured_us = data->next_timer_us;
 
-	} else {
-		/* Use measured value */
-		measured_us = cpuidle_get_last_residency(dev);
+	/* measured value */
+	measured_us = cpuidle_get_last_residency(dev);
 
-		/* Deduct exit latency */
-		if (measured_us > target->exit_latency)
-			measured_us -= target->exit_latency;
+	/* Deduct exit latency */
+	if (measured_us > target->exit_latency)
+		measured_us -= target->exit_latency;
 
-		/* Make sure our coefficients do not exceed unity */
-		if (measured_us > data->next_timer_us)
-			measured_us = data->next_timer_us;
-	}
+	/* Make sure our coefficients do not exceed unity */
+	if (measured_us > data->next_timer_us)
+		measured_us = data->next_timer_us;
 
 	/* Update our correction ratio */
 	new_factor = data->correction_factor[data->bucket];
-- 
2.1.2.451.g98349e5

[PATCH 2/3] cpuidle ladder: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID

[Len Brown]

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

When the ladder governor sees the CPUIDLE_FLAG_TIME_INVALID flag,
it unconditionally causes a state promotion by setting last_residency
to a number higher than the state's promotion_time:

last_residency = last_state->threshold.promotion_time + 1

It does this for fear that cpuidle_get_last_residency()
will be in-accurate, because cpuidle_enter_state() invoked
a state with CPUIDLE_FLAG_TIME_INVALID.

But the only state with CPUIDLE_FLAG_TIME_INVALID is
acpi_safe_halt(), which may return well after its actual
idle duration because it enables interrupts, so cpuidle_enter_state()
also measures interrupt service time.

So what?  In ladder, a huge invalid last_residency has exactly
the same effect as the current code -- it unconditionally
causes a state promotion.

In the case where the idle residency plus measured interrupt
handling time is less than the state's demotion_time -- we should
use that timestamp to give ladder a chance to demote, rather than
unconditionally promoting.

This can be done by simply ignoring the CPUIDLE_FLAG_TIME_INVALID,
and using the "invalid" time, as it is either equal to what we are
doing today, or better.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/cpuidle/governors/ladder.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index 37263d9..401c010 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -79,12 +79,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
 
 	last_state = &ldev->states[last_idx];
 
-	if (!(drv->states[last_idx].flags & CPUIDLE_FLAG_TIME_INVALID)) {
-		last_residency = cpuidle_get_last_residency(dev) - \
-					 drv->states[last_idx].exit_latency;
-	}
-	else
-		last_residency = last_state->threshold.promotion_time + 1;
+	last_residency = cpuidle_get_last_residency(dev) - drv->states[last_idx].exit_latency;
 
 	/* consider promotion */
 	if (last_idx < drv->state_count - 1 &&
-- 
2.1.2.451.g98349e5

Re: [PATCH 2/3] cpuidle ladder: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID

[Daniel Lezcano]

On 12/16/2014 07:52 AM, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
>
> When the ladder governor sees the CPUIDLE_FLAG_TIME_INVALID flag,
> it unconditionally causes a state promotion by setting last_residency
> to a number higher than the state's promotion_time:
>
> last_residency = last_state->threshold.promotion_time + 1
>
> It does this for fear that cpuidle_get_last_residency()
> will be in-accurate, because cpuidle_enter_state() invoked
> a state with CPUIDLE_FLAG_TIME_INVALID.
>
> But the only state with CPUIDLE_FLAG_TIME_INVALID is
> acpi_safe_halt(), which may return well after its actual
> idle duration because it enables interrupts, so cpuidle_enter_state()
> also measures interrupt service time.
>
> So what?  In ladder, a huge invalid last_residency has exactly
> the same effect as the current code -- it unconditionally
> causes a state promotion.
>
> In the case where the idle residency plus measured interrupt
> handling time is less than the state's demotion_time -- we should
> use that timestamp to give ladder a chance to demote, rather than
> unconditionally promoting.
>
> This can be done by simply ignoring the CPUIDLE_FLAG_TIME_INVALID,
> and using the "invalid" time, as it is either equal to what we are
> doing today, or better.
>
> Signed-off-by: Len Brown <len.brown@intel.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>

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

a dumb question: is someone still using the ladder governor nowadays ?

> ---
>   drivers/cpuidle/governors/ladder.c | 7 +------
>   1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
> index 37263d9..401c010 100644
> --- a/drivers/cpuidle/governors/ladder.c
> +++ b/drivers/cpuidle/governors/ladder.c
> @@ -79,12 +79,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
>
>   	last_state = &ldev->states[last_idx];
>
> -	if (!(drv->states[last_idx].flags & CPUIDLE_FLAG_TIME_INVALID)) {
> -		last_residency = cpuidle_get_last_residency(dev) - \
> -					 drv->states[last_idx].exit_latency;
> -	}
> -	else
> -		last_residency = last_state->threshold.promotion_time + 1;
> +	last_residency = cpuidle_get_last_residency(dev) - drv->states[last_idx].exit_latency;
>
>   	/* consider promotion */
>   	if (last_idx < drv->state_count - 1 &&
>


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[PATCH 3/3] cpuidle, ACPI: remove unused CPUIDLE_FLAG_TIME_INVALID

[Len Brown]

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

CPUIDLE_FLAG_TIME_INVALID is no longer checked
by menu or ladder cpuidle governors, so don't
bother setting or defining it.

It was originally invented to account for the fact that
acpi_safe_halt() enables interrupts to invoke HLT.
That would allow interrupt service routines to be included
in the last_idle duration measurements made in cpuidle_enter_state(),
potentially returning a duration much larger than reality.

But menu and ladder can gracefully handle erroneously large duration
intervals without checking for CPUIDLE_FLAG_TIME_INVALID.
Further, if they don't check CPUIDLE_FLAG_TIME_INVALID, they
can also benefit from the instances when the duration interval
is not erroneously large.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/acpi/processor_idle.c | 2 --
 include/linux/cpuidle.h       | 3 ---
 2 files changed, 5 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 4995365..87b704e 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -985,8 +985,6 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
 		state->flags = 0;
 		switch (cx->type) {
 			case ACPI_STATE_C1:
-			if (cx->entry_method != ACPI_CSTATE_FFH)
-				state->flags |= CPUIDLE_FLAG_TIME_INVALID;
 
 			state->enter = acpi_idle_enter_c1;
 			state->enter_dead = acpi_idle_play_dead;
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index a07e087..ab70f3b 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -53,7 +53,6 @@ struct cpuidle_state {
 };
 
 /* Idle State Flags */
-#define CPUIDLE_FLAG_TIME_INVALID	(0x01) /* is residency time measurable? */
 #define CPUIDLE_FLAG_COUPLED	(0x02) /* state applies to multiple cpus */
 #define CPUIDLE_FLAG_TIMER_STOP (0x04)  /* timer is stopped on this state */
 
@@ -89,8 +88,6 @@ DECLARE_PER_CPU(struct cpuidle_device, cpuidle_dev);
 /**
  * cpuidle_get_last_residency - retrieves the last state's residency time
  * @dev: the target CPU
- *
- * NOTE: this value is invalid if CPUIDLE_FLAG_TIME_INVALID is set
  */
 static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
 {
-- 
2.1.2.451.g98349e5

Re: [PATCH 3/3] cpuidle, ACPI: remove unused CPUIDLE_FLAG_TIME_INVALID

[Daniel Lezcano]

On 12/16/2014 07:52 AM, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
>
> CPUIDLE_FLAG_TIME_INVALID is no longer checked
> by menu or ladder cpuidle governors, so don't
> bother setting or defining it.
>
> It was originally invented to account for the fact that
> acpi_safe_halt() enables interrupts to invoke HLT.
> That would allow interrupt service routines to be included
> in the last_idle duration measurements made in cpuidle_enter_state(),
> potentially returning a duration much larger than reality.
>
> But menu and ladder can gracefully handle erroneously large duration
> intervals without checking for CPUIDLE_FLAG_TIME_INVALID.
> Further, if they don't check CPUIDLE_FLAG_TIME_INVALID, they
> can also benefit from the instances when the duration interval
> is not erroneously large.
>
> Signed-off-by: Len Brown <len.brown@intel.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>

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


> ---
>   drivers/acpi/processor_idle.c | 2 --
>   include/linux/cpuidle.h       | 3 ---
>   2 files changed, 5 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 4995365..87b704e 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -985,8 +985,6 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
>   		state->flags = 0;
>   		switch (cx->type) {
>   			case ACPI_STATE_C1:
> -			if (cx->entry_method != ACPI_CSTATE_FFH)
> -				state->flags |= CPUIDLE_FLAG_TIME_INVALID;
>
>   			state->enter = acpi_idle_enter_c1;
>   			state->enter_dead = acpi_idle_play_dead;
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index a07e087..ab70f3b 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -53,7 +53,6 @@ struct cpuidle_state {
>   };
>
>   /* Idle State Flags */
> -#define CPUIDLE_FLAG_TIME_INVALID	(0x01) /* is residency time measurable? */
>   #define CPUIDLE_FLAG_COUPLED	(0x02) /* state applies to multiple cpus */
>   #define CPUIDLE_FLAG_TIMER_STOP (0x04)  /* timer is stopped on this state */
>
> @@ -89,8 +88,6 @@ DECLARE_PER_CPU(struct cpuidle_device, cpuidle_dev);
>   /**
>    * cpuidle_get_last_residency - retrieves the last state's residency time
>    * @dev: the target CPU
> - *
> - * NOTE: this value is invalid if CPUIDLE_FLAG_TIME_INVALID is set
>    */
>   static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
>   {
>


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Re: [PATCH 3/3] cpuidle, ACPI: remove unused CPUIDLE_FLAG_TIME_INVALID

[Rafael J. Wysocki]

On Tuesday, December 16, 2014 12:08:25 PM Daniel Lezcano wrote:
> On 12/16/2014 07:52 AM, Len Brown wrote:
> > From: Len Brown <len.brown@intel.com>
> >
> > CPUIDLE_FLAG_TIME_INVALID is no longer checked
> > by menu or ladder cpuidle governors, so don't
> > bother setting or defining it.
> >
> > It was originally invented to account for the fact that
> > acpi_safe_halt() enables interrupts to invoke HLT.
> > That would allow interrupt service routines to be included
> > in the last_idle duration measurements made in cpuidle_enter_state(),
> > potentially returning a duration much larger than reality.
> >
> > But menu and ladder can gracefully handle erroneously large duration
> > intervals without checking for CPUIDLE_FLAG_TIME_INVALID.
> > Further, if they don't check CPUIDLE_FLAG_TIME_INVALID, they
> > can also benefit from the instances when the duration interval
> > is not erroneously large.
> >
> > Signed-off-by: Len Brown <len.brown@intel.com>
> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> 
> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

OK

Since the material for my next pull request is staged already, I'm going to
queue up this series for 3.19-rc, but I'll most likely push it for -rc2.

Thanks!

> > ---
> >   drivers/acpi/processor_idle.c | 2 --
> >   include/linux/cpuidle.h       | 3 ---
> >   2 files changed, 5 deletions(-)
> >
> > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> > index 4995365..87b704e 100644
> > --- a/drivers/acpi/processor_idle.c
> > +++ b/drivers/acpi/processor_idle.c
> > @@ -985,8 +985,6 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
> >   		state->flags = 0;
> >   		switch (cx->type) {
> >   			case ACPI_STATE_C1:
> > -			if (cx->entry_method != ACPI_CSTATE_FFH)
> > -				state->flags |= CPUIDLE_FLAG_TIME_INVALID;
> >
> >   			state->enter = acpi_idle_enter_c1;
> >   			state->enter_dead = acpi_idle_play_dead;
> > diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> > index a07e087..ab70f3b 100644
> > --- a/include/linux/cpuidle.h
> > +++ b/include/linux/cpuidle.h
> > @@ -53,7 +53,6 @@ struct cpuidle_state {
> >   };
> >
> >   /* Idle State Flags */
> > -#define CPUIDLE_FLAG_TIME_INVALID	(0x01) /* is residency time measurable? */
> >   #define CPUIDLE_FLAG_COUPLED	(0x02) /* state applies to multiple cpus */
> >   #define CPUIDLE_FLAG_TIMER_STOP (0x04)  /* timer is stopped on this state */
> >
> > @@ -89,8 +88,6 @@ DECLARE_PER_CPU(struct cpuidle_device, cpuidle_dev);
> >   /**
> >    * cpuidle_get_last_residency - retrieves the last state's residency time
> >    * @dev: the target CPU
> > - *
> > - * NOTE: this value is invalid if CPUIDLE_FLAG_TIME_INVALID is set
> >    */
> >   static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
> >   {
> >
> 
> 
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 1/3] cpuidle menu: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID

[Daniel Lezcano]

On 12/16/2014 07:52 AM, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
>
> When menu sees CPUIDLE_FLAG_TIME_INVALID, it ignores its timestamps,
> and assumes that idle lasted as long as the time till next predicted
> timer expiration.
>
> But if an interrupt was seen and serviced before that duration,
> it would actually be more accurate to use the measured time
> rather than rounding up to the next predicted timer expiration.
>
> And if an interrupt is seen and serviced such that the mesured time
> exceeds the time till next predicted timer expiration, then
> truncating to that expiration is the right thing to do --
> since we can never stay idle past that timer expiration.
>
> So the code can do a better job without
> checking for CPUIDLE_FLAG_TIME_INVALID.

Good point.

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

> Signed-off-by: Len Brown <len.brown@intel.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>   drivers/cpuidle/governors/menu.c | 25 ++++++++++---------------
>   1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index 659d7b0..4058079 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -396,8 +396,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>   	 * power state and occurrence of the wakeup event.
>   	 *
>   	 * If the entered idle state didn't support residency measurements,
> -	 * we are basically lost in the dark how much time passed.
> -	 * As a compromise, assume we slept for the whole expected time.
> +	 * we use them anyway if they are short, and if long,
> +	 * truncate to the whole expected time.
>   	 *
>   	 * Any measured amount of time will include the exit latency.
>   	 * Since we are interested in when the wakeup begun, not when it
> @@ -405,22 +405,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>   	 * the measured amount of time is less than the exit latency,
>   	 * assume the state was never reached and the exit latency is 0.
>   	 */
> -	if (unlikely(target->flags & CPUIDLE_FLAG_TIME_INVALID)) {
> -		/* Use timer value as is */
> -		measured_us = data->next_timer_us;
>
> -	} else {
> -		/* Use measured value */
> -		measured_us = cpuidle_get_last_residency(dev);
> +	/* measured value */
> +	measured_us = cpuidle_get_last_residency(dev);
>
> -		/* Deduct exit latency */
> -		if (measured_us > target->exit_latency)
> -			measured_us -= target->exit_latency;
> +	/* Deduct exit latency */
> +	if (measured_us > target->exit_latency)
> +		measured_us -= target->exit_latency;
>
> -		/* Make sure our coefficients do not exceed unity */
> -		if (measured_us > data->next_timer_us)
> -			measured_us = data->next_timer_us;
> -	}
> +	/* Make sure our coefficients do not exceed unity */
> +	if (measured_us > data->next_timer_us)
> +		measured_us = data->next_timer_us;
>
>   	/* Update our correction ratio */
>   	new_factor = data->correction_factor[data->bucket];
>


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Re: [PATCH 1/3] cpuidle menu: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID

[Tuukka Tikkanen]

On Tue, Dec 16, 2014 at 8:52 AM, Len Brown <lenb@kernel.org> wrote:
> From: Len Brown <len.brown@intel.com>
>
> When menu sees CPUIDLE_FLAG_TIME_INVALID, it ignores its timestamps,
> and assumes that idle lasted as long as the time till next predicted
> timer expiration.
>
> But if an interrupt was seen and serviced before that duration,
> it would actually be more accurate to use the measured time
> rather than rounding up to the next predicted timer expiration.
>
> And if an interrupt is seen and serviced such that the mesured time
> exceeds the time till next predicted timer expiration, then
> truncating to that expiration is the right thing to do --
> since we can never stay idle past that timer expiration.
>
> So the code can do a better job without
> checking for CPUIDLE_FLAG_TIME_INVALID.
>
> Signed-off-by: Len Brown <len.brown@intel.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>

Reviewed-by: Tuukka Tikkanen <tuukka.tikkanen@linaro.org>

> ---
>  drivers/cpuidle/governors/menu.c | 25 ++++++++++---------------
>  1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index 659d7b0..4058079 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -396,8 +396,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>          * power state and occurrence of the wakeup event.
>          *
>          * If the entered idle state didn't support residency measurements,
> -        * we are basically lost in the dark how much time passed.
> -        * As a compromise, assume we slept for the whole expected time.
> +        * we use them anyway if they are short, and if long,
> +        * truncate to the whole expected time.
>          *
>          * Any measured amount of time will include the exit latency.
>          * Since we are interested in when the wakeup begun, not when it
> @@ -405,22 +405,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>          * the measured amount of time is less than the exit latency,
>          * assume the state was never reached and the exit latency is 0.
>          */
> -       if (unlikely(target->flags & CPUIDLE_FLAG_TIME_INVALID)) {
> -               /* Use timer value as is */
> -               measured_us = data->next_timer_us;
>
> -       } else {
> -               /* Use measured value */
> -               measured_us = cpuidle_get_last_residency(dev);
> +       /* measured value */
> +       measured_us = cpuidle_get_last_residency(dev);
>
> -               /* Deduct exit latency */
> -               if (measured_us > target->exit_latency)
> -                       measured_us -= target->exit_latency;
> +       /* Deduct exit latency */
> +       if (measured_us > target->exit_latency)
> +               measured_us -= target->exit_latency;
>
> -               /* Make sure our coefficients do not exceed unity */
> -               if (measured_us > data->next_timer_us)
> -                       measured_us = data->next_timer_us;
> -       }
> +       /* Make sure our coefficients do not exceed unity */
> +       if (measured_us > data->next_timer_us)
> +               measured_us = data->next_timer_us;
>
>         /* Update our correction ratio */
>         new_factor = data->correction_factor[data->bucket];
> --
> 2.1.2.451.g98349e5
>
> --
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