Commit f49735f4 authored by Lina Iyer's avatar Lina Iyer Committed by Rafael J. Wysocki
Browse files

cpuidle: record state entry rejection statistics 



CPUs may fail to enter the chosen idle state if there was a
pending interrupt, causing the cpuidle driver to return an error
value.

Record that and export it via sysfs along with the other idle state
statistics.

This could prove useful in understanding behavior of the governor
and the system during usecases that involve multiple CPUs.

Signed-off-by: default avatarLina Iyer <ilina@codeaurora.org>
[ rjw: Changelog and documentation edits ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 70c179b4

Documentation/admin-guide/pm/cpuidle.rst

+9 −0
Original line number Diff line number Diff line
@@ -528,6 +528,10 @@ object corresponding to it, as follows: 
	Total number of times the hardware has been asked by the given CPU to

	enter this idle state.



``rejected``

	Total number of times a request to enter this idle state on the given

	CPU was rejected.



The :file:`desc` and :file:`name` files both contain strings.  The difference

between them is that the name is expected to be more concise, while the

description may be longer and it may contain white space or special characters.
@@ -572,6 +576,11 @@ particular case. For these reasons, the only reliable way to find out how 
much time has been spent by the hardware in different idle states supported by

it is to use idle state residency counters in the hardware, if available.



Generally, an interrupt received when trying to enter an idle state causes the

idle state entry request to be rejected, in which case the ``CPUIdle`` driver

may return an error code to indicate that this was the case. The :file:`usage`

and :file:`rejected` files report the number of times the given idle state

was entered successfully or rejected, respectively.



.. _cpu-pm-qos:

drivers/cpuidle/cpuidle.c

+1 −0
Original line number Diff line number Diff line
@@ -307,6 +307,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, 
		}

	} else {

		dev->last_residency_ns = 0;

		dev->states_usage[index].rejected++;

	}



	return entered_state;

drivers/cpuidle/sysfs.c

+3 −0
Original line number Diff line number Diff line
@@ -256,6 +256,7 @@ define_show_state_time_function(exit_latency) 
define_show_state_time_function(target_residency)

define_show_state_function(power_usage)

define_show_state_ull_function(usage)

define_show_state_ull_function(rejected)

define_show_state_str_function(name)

define_show_state_str_function(desc)

define_show_state_ull_function(above)
@@ -312,6 +313,7 @@ define_one_state_ro(latency, show_state_exit_latency); 
define_one_state_ro(residency, show_state_target_residency);

define_one_state_ro(power, show_state_power_usage);

define_one_state_ro(usage, show_state_usage);

define_one_state_ro(rejected, show_state_rejected);

define_one_state_ro(time, show_state_time);

define_one_state_rw(disable, show_state_disable, store_state_disable);

define_one_state_ro(above, show_state_above);
@@ -325,6 +327,7 @@ static struct attribute *cpuidle_state_default_attrs[] = { 
	&attr_residency.attr,

	&attr_power.attr,

	&attr_usage.attr,

	&attr_rejected.attr,

	&attr_time.attr,

	&attr_disable.attr,

	&attr_above.attr,

include/linux/cpuidle.h

+1 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ struct cpuidle_state_usage { 
	u64			time_ns;

	unsigned long long	above; /* Number of times it's been too deep */

	unsigned long long	below; /* Number of times it's been too shallow */

	unsigned long long	rejected; /* Number of times idle entry was rejected */

#ifdef CONFIG_SUSPEND

	unsigned long long	s2idle_usage;

	unsigned long long	s2idle_time; /* in US */

CRA Git | Maintained and supported by SUSTech CRA and CCSE