From f49735f4978f479b0de4f50ab217d5a56bc83c55 Mon Sep 17 00:00:00 2001 From: Lina Iyer Date: Tue, 22 Sep 2020 12:34:16 -0600 Subject: [PATCH] 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: Lina Iyer [ rjw: Changelog and documentation edits ] Signed-off-by: Rafael J. Wysocki --- Documentation/admin-guide/pm/cpuidle.rst | 9 +++++++++ drivers/cpuidle/cpuidle.c | 1 + drivers/cpuidle/sysfs.c | 3 +++ include/linux/cpuidle.h | 1 + 4 files changed, 14 insertions(+) diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst index a96a423e3779..830868e526f4 100644 --- a/Documentation/admin-guide/pm/cpuidle.rst +++ b/Documentation/admin-guide/pm/cpuidle.rst @@ -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: diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 6c7e5621cf9a..0ed5030b89d6 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -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; diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c index 091d1caceb41..53ec9585ccd4 100644 --- a/drivers/cpuidle/sysfs.c +++ b/drivers/cpuidle/sysfs.c @@ -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, diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 6175c77bf25e..ed0da0e58e8b 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -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 */