[PATCH v2 1/3] Documentation: add description of forceidle time statistics

[Cruz Zhao <CruzZhao@linux.alibaba.com>]

Add description of forceidle time statistics, including task perspective
and cgroup perspective.

Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com>
---
 Documentation/admin-guide/cgroup-v2.rst       |  3 ++-
 .../admin-guide/hw-vuln/core-scheduling.rst   | 24 +++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 17e6e9565156..b82717767c61 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1081,8 +1081,9 @@ All time durations are in microseconds.
 	- user_usec
 	- system_usec
 
-	and the following five when the controller is enabled:
+	and the following six when the controller is enabled:
 
+	- core_sched.force_idle_usec
 	- nr_periods
 	- nr_throttled
 	- throttled_usec
diff --git a/Documentation/admin-guide/hw-vuln/core-scheduling.rst b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
index cf1eeefdfc32..95a4920a2a9b 100644
--- a/Documentation/admin-guide/hw-vuln/core-scheduling.rst
+++ b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
@@ -224,3 +224,27 @@ with SMT enabled. There are other use cases where this feature could be used:
 - Gang scheduling: Requirements for a group of tasks that needs to be scheduled
   together could also be realized using core scheduling. One example is vCPUs of
   a VM.
+
+Statictics
+----------
+A task's forceidle statistics are exported via 1 field in procfs.
+
+/proc/$pid/sched:
+
+ - se.statistics.core_forceidle_sum: Force idle time caused by this task,
+   unit: ms. It is worth noting that, if this task is running on cpux whose SMT
+   siblings are forced idle, the irq time of cpux during this period will be
+   accounted to this task's force idle time.
+
+This interface is read-only.
+
+A group's forceidle statistics are exported via 1 filed in cpu.stat.
+
+cpu.stat:
+
+ - core_sched.force_idle_usec: Force idle time caused by this cgroup' tasks,
+   unit: us. It is worth nothing that, if this cgroup's task is running on cpux
+   whose SMT siblings are forced idle, the irq time of cpux during this period
+   will be accounted to this cgroup's force idle time.
+
+This interface is read-only.
-- 
2.39.3