[PATCH 8/8] Documentation: page_owner: Document PID/TGID/COMM and cgroup filters

[Zhen Ni <zhen.ni@easystack.cn>]

Update page_owner.rst to document process and cgroup filtering
support in page_owner_filter tool. Add usage examples for PID, TGID,
COMM (with wildcard support), and cgroup filters along with their
respective limits.

Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
---
 Documentation/mm/page_owner.rst | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/mm/page_owner.rst b/Documentation/mm/page_owner.rst
index a6bd3fe6423a..c8a7e6c242c5 100644
--- a/Documentation/mm/page_owner.rst
+++ b/Documentation/mm/page_owner.rst
@@ -283,7 +283,7 @@ page_owner supports filtering output at the kernel level before reading,
 which reduces the amount of data that needs to be processed in userspace.
 
 The page_owner_filter tool provides a convenient interface for this filtering
-capability. It supports two types of filters:
+capability. It supports the following types of filters:
 
 1. **print_mode filter**: Control what information is printed for each page
 	- ``stack``: Print full stack traces (default, compatible with existing usage)
@@ -300,6 +300,16 @@ capability. It supports two types of filters:
 	- Ranges: ``-n 0-3``
 	- Mixed format: ``-n 0,2-3,5``
 
+3. **Process filters**: Filter pages by process identifiers
+	- Filter by process ID: ``-p PID_LIST`` (comma-separated, max 16)
+	- Filter by thread group ID: ``-t TGID_LIST`` (comma-separated, max 16)
+	- Filter by task command name: ``-c COMM_LIST`` (comma-separated, max 8)
+	- Name matching supports wildcards: ``*``, ``?``, ``[a-z]``
+
+4. **Cgroup (memcg) filter**: Filter pages by memory cgroup
+	- Filter by cgroup path: ``-g CGROUP``
+	- Useful for containerized environments and multi-tenant systems
+
 Usage examples::
 
 	# Filter by print mode
@@ -310,9 +320,19 @@ Usage examples::
 	./page_owner_filter -n 0
 	./page_owner_filter -n 0-3
 
+	# Filter by process
+	./page_owner_filter -p 1234
+	./page_owner_filter -t 1,2,3
+	./page_owner_filter -c python*
+
+	# Filter by cgroup
+	./page_owner_filter -g system.slice
+	./page_owner_filter -g kubepods/besteffort/pod123
+
 	# Combined filters
 	./page_owner_filter -m stack -n 0,1,2
 	./page_owner_filter -m handle -n 0,2-3
+	./page_owner_filter -g user.slice -c bash -n 0
 
 	# Save to file
 	./page_owner_filter -m handle -o filtered_output.txt
@@ -323,6 +343,9 @@ reduce output size by ~66% (84MB vs 244MB) and improve read performance by ~4.4x
 compared to full stack output.
 
 The NUMA node filter is useful for NUMA-aware memory allocation analysis and debugging.
+Process filters help isolate memory allocations for specific processes or tasks.
+The cgroup filter is essential for containerized environments where you need to
+analyze memory usage per container or service.
 
 Behind the scenes, page_owner_filter opens /sys/kernel/debug/page_owner and
 writes filter commands before reading the filtered output. The filtering uses
-- 
2.20.1