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authorLina Iyer <ilina@codeaurora.org>2020-09-22 21:34:16 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-09-23 15:10:31 +0300
commitf49735f4978f479b0de4f50ab217d5a56bc83c55 (patch)
treeff16650624327711ecff8d9a6b2b885585dd9245 /Documentation/admin-guide/pm
parent70c179b49870929ca183421935415622d30875b5 (diff)
downloadlinux-f49735f4978f479b0de4f50ab217d5a56bc83c55.tar.xz
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 <ilina@codeaurora.org> [ rjw: Changelog and documentation edits ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/admin-guide/pm')
-rw-r--r--Documentation/admin-guide/pm/cpuidle.rst9
1 files changed, 9 insertions, 0 deletions
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: