[PATCH v4 8/9] Docs/admin-guide/cgroup-v2: document workingset reporting

[Yuanchu Xie <yuanchu@google.com>]

Add workingset reporting documentation for better discoverability of
its memcg interfaces. Point the memcg documentation to
Documentation/admin-guide/mm/workingset_report.rst for more details.

Signed-off-by: Yuanchu Xie <yuanchu@google.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 35 +++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 2cb58daf3089..67a183f08245 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1784,6 +1784,41 @@ The following nested keys are defined.
 	Shows pressure stall information for memory. See
 	:ref:`Documentation/accounting/psi.rst <psi>` for details.
 
+  memory.workingset.page_age
+	A read-only histogram which exists on non-root cgroups.
+
+	This breaks down the cgroup's memory footprint into different
+	types of memory and groups them per-node into user-defined coldness
+	bins.
+
+	The output format of memory.workingset.page_age is::
+
+	  N0
+	  <interval 0 of node 0> type=<type bytes in interval 0 of node 0>
+	  <interval 1 of node 0> type=<type bytes in interval 1 of node 0>
+	  ...
+	  18446744073709551615 type=<the rest of type bytes of node 0>
+
+	The type of memory can be anon, file, or new types added later.
+	Don't rely on the types remaining fixed.  See
+	:ref:`Documentation/admin-guide/mm/workingset_report.rst <workingset_report>`
+	for details.
+
+  memory.workingset.refresh_interval
+	A read-write nested-keyed file which exists on non-root cgroups.
+
+	Setting it to a non-zero value for any node enables working set
+	reporting for that node.  The default is 0 for each node.   See
+	:ref:`Documentation/admin-guide/mm/workingset_report.rst <workingset_report>`
+	for details.
+
+  memory.workingset.report_threshold
+	A read-write nested-keyed file which exists on non-root cgroups.
+
+	The amount of milliseconds to wait before reporting the working
+	set again.  The default is 0 for each node.  See
+	:ref:`Documentation/admin-guide/mm/workingset_report.rst <workingset_report>`
+	for details.
 
 Usage Guidelines
 ~~~~~~~~~~~~~~~~
-- 
2.47.0.338.g60cca15819-goog