On Tue, Sep 22, 2020 at 8:34 PM Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote:
>
> CPUs may fail to enter the chosen idle state if there was a pending
> interrupt. The cpuidle driver would return an error value in that case.
> Let's record that and show along with other statistics for the idle
> state. This could prove useful in understanding behavior of the governor
> and the system during usecases that involve multiple CPUs.
>
> Signed-off-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>
Applied as 5.10 material with some changelog and documentation edits, thanks!
>
> ---
> Changes in v2:
> - Rename 'failed' to 'rejected'
> - Update documentation
> ---
> Documentation/admin-guide/pm/cpuidle.rst | 8 ++++++++
> drivers/cpuidle/cpuidle.c | 1 +
> drivers/cpuidle/sysfs.c | 3 +++
> include/linux/cpuidle.h | 1 +
> 4 files changed, 13 insertions(+)
>
> diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst
> index a96a423e3779..1e7fd7a64c65 100644
> --- a/Documentation/admin-guide/pm/cpuidle.rst
> +++ b/Documentation/admin-guide/pm/cpuidle.rst
> @@ -528,6 +528,9 @@ 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 the idle state requested to the 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 +575,11 @@ 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 entering idle state would cause the idle
> +state entry request to be rejected. The return value from the cpuidle driver
> +indicates whether the idle state was entered or rejected. The files
> +:file:`usage` and :file:`rejected` report the number of times the idle states
> +were successfully entered and 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 */
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
