[PATCH] cgroup/cpu: document cpu.stat.local

[Sun Shaojie]

Add documentation for the cpu.stat.local interface file, which reports
the throttled_usec stat -- the actual throttling time incurred by the
cgroup's own runqueues, which may include throttling inherited from
ancestor cgroup bandwidth limits. Unlike cpu.stat's throttled_usec
which only accounts for throttling caused by the cgroup's own CFS
bandwidth limit.

When the controller is not enabled, the stat is not reported.

Signed-off-by: Sun Shaojie <sunshaojie@xxxxxxxxxx>
---
 Documentation/admin-guide/cgroup-v2.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 993446ab66d0..a7766f40ef65 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1160,6 +1160,23 @@ will be referred to. All time durations are in microseconds.
 	- nr_bursts
 	- burst_usec
 
+  cpu.stat.local
+	A read-only flat-keyed file which exists on non-root cgroups.
+	This file exists whether the controller is enabled or not.
+
+	It reports the following stat when the controller is enabled:
+
+	- throttled_usec
+
+	Unlike the ``throttled_usec`` reported by ``cpu.stat`` which
+	accounts for throttling caused by this cgroup's own CFS
+	bandwidth limit, ``cpu.stat.local`` reports the actual
+	throttling time incurred by this cgroup's own runqueues,
+	which may include throttling inherited from ancestor
+	cgroup bandwidth limits.
+
+	When the controller is not enabled, this stat is not reported.
+
   cpu.weight
 	A read-write single value file which exists on non-root
 	cgroups.  The default is "100".
-- 
2.25.1