Re: [PATCH] cpuidle: record state entry failed statistics

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On Tue, Sep 22 2020 at 09:57 -0600, Rafael J. Wysocki wrote:
Sorry for the delay.

Thanks for the review.

On Wed, Sep 2, 2020 at 11:01 PM Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote:

When CPUs fail to enter the chosen idle state it's mostly because of a
pending interrupt. 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>
---
 drivers/cpuidle/cpuidle.c | 1 +
 drivers/cpuidle/sysfs.c   | 3 +++
 include/linux/cpuidle.h   | 1 +

The documentation needs to be updated too to cover the new state attribute.

Sure, will add that in the next spin.
 3 files changed, 5 insertions(+)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 04becd70cc41..8dbf71f6138d 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -302,6 +302,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
                }
        } else {
                dev->last_residency_ns = 0;
+               dev->states_usage[index].failed++;
        }

        return entered_state;
diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 091d1caceb41..f166687b3bcd 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(failed)

And what about calling it "rejected" instead of "failed"?

Works for me.

Thanks,
Lina

 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(failed, show_state_failed);
 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_failed.attr,
        &attr_time.attr,
        &attr_disable.attr,
        &attr_above.attr,
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 75895e6363b8..911b99273eba 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      failed; /* Number of times it failed to enter */
 #ifdef CONFIG_SUSPEND
        unsigned long long      s2idle_usage;
        unsigned long long      s2idle_time; /* in US */
--
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a Linux Foundation Collaborative Project




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