[to-be-updated] mm-page_owner-add-filter-infrastructure.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

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The quilt patch titled
     Subject: mm/page_owner: add filter infrastructure
has been removed from the -mm tree.  Its filename was
     mm-page_owner-add-filter-infrastructure.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: Zhen Ni <zhen.ni@easystack.cn>
Subject: mm/page_owner: add filter infrastructure
Date: Sun, 19 Apr 2026 23:55:38 +0800

Patch series "mm/page_owner: add filter infrastructure for print_mode and
NUMA filtering", v2.

This patch series introduces filtering capabilities to the page_owner
feature to address storage and performance challenges in production
environments.

Changes from v1:
- Renamed 'compact' to 'print_mode' with enum type for better clarity
  * PAGE_OWNER_PRINT_FULL_STACK (0): print full stack traces
  * PAGE_OWNER_PRINT_STACK_HANDLE (1): print only stack handles
- Changed NUMA filter from single node to nodelist with bitmask support
  * Uses nodelist_parse() to support "0", "0,2", "0-3", "0,2-4,7" formats
  * Uses nodemask_t internally for efficient multi-node filtering
  * Output uses %*pbl format (e.g., "0-2", "0,2-4,7")
- Improved memory handling in nid_filter_write using dynamic allocation
  * Limit: (100 + 6 * MAX_NUMNODES) to handle worst-case input

These changes address feedback from v1 review:
- "compact" was too vague → use descriptive enum (PAGE_OWNER_PRINT_*)
- Single node filter was limiting → use nodelist_parse() for multi-node support

Problem Statement
=================

In production environments with large memory configurations (e.g.,
250GB+), collecting page_owner information often results in files ranging
from several gigabytes to over 10GB.  This creates significant challenges:

1. Storage pressure on production systems
2. Difficulty transferring large files from production environments
3. Post-processing overhead with tools/mm/page_owner_sort.c

The primary contributor to file size is redundant stack trace information.
While the kernel already deduplicates stacks via stackdepot, page_owner
retrieves and stores full stack traces for each page, only to deduplicate
them again during post-processing.

Additionally, in NUMA-aware environments (e.g., DPDK-based cloud
deployments where QEMU processes are bound to specific NUMA nodes), OOM
events are often node-specific rather than system-wide.  Currently,
page_owner cannot filter by NUMA node, forcing users to collect and
analyze data for all nodes.

Solution
========

This patch series introduces a flexible filter infrastructure with
two initial filters:

1. **Print Mode Filter**: Outputs only stack handles instead of
   full stack traces. The handle-to-stack mapping can be retrieved
   from the existing show_stacks_handles interface. This dramatically
   reduces output size while preserving all allocation metadata.

2. **NUMA Node Filter**: Allows filtering pages by specific NUMA node(s)
   using flexible nodelist format, enabling targeted analysis of memory
   issues in NUMA-aware deployments.

Implementation
==============

The series is structured as follows:

- Patch 1: Add filter infrastructure (data structures and
  debugfs directory)
- Patch 2: Implement print_mode filter
- Patch 3: Implement NUMA node filter with nodelist support

Usage Example
=============

Enable print_mode and filter for NUMA nodes 0,2-3:

    # cd /sys/kernel/debug/page_owner_filter/
    # echo 1 > print_mode
    # echo "0,2-3" > nid
    # cat /sys/kernel/debug/page_owner > page_owner.txt

Sample print_mode output (showing handles only):

    Page allocated via order 0, mask 0x0(), pid 0, tgid 0 (swapper),
    ts 0 ns PFN 0x40000 type Unmovable Block 512 type Unmovable
    Flags 0x3fffe0000000000(node=0|zone=0|lastcpupid=0x1ffff)
    handle: 1048577

    Page allocated via order 0, mask 0x252000(__GFP_NOWARN|
    __GFP_NORETRY|__GFP_COMP|__GFP_THISNODE), pid 0, tgid 0 (swapper),
    ts 0 ns PFN 0x40002 type Unmovable Block 512 type Unmovable
    Flags 0x23fffe0000000200(workingset|node=0|zone=0|lastcpupid=0x1ffff)
    handle: 1048577

Testing
=======

Tested on a system with multiple NUMA nodes. Verified that:
- Filters work independently and in combination
- Print_mode output correlates correctly with show_stacks_handles
- Default behavior (filters disabled) remains unchanged
- NUMA filter works with single node, multiple nodes, and ranges

Example test session:
    # cat print_mode
    0
    # echo "0,1-2" > nid
    # cat nid
    0-2
    # echo "0,2-3" > nid
    # cat nid
    0,2-3
    # echo 1 > print_mode
    # head -n 100 /sys/kernel/debug/page_owner
    [Shows compact mode output with handles only]

Future Enhancements
==================

The filter infrastructure is designed to be extensible. Potential
future filters could include:
- PID/TGID filtering
- Time range filtering (allocation timestamp windows)
- GFP flag filtering
- Migration type filtering


This patch (of 3):

Add data structure for page_owner filtering functionality and create
debugfs directory for filter controls.

This adds:
- enum page_owner_print_mode with values for full_stack and stack_handle
- struct page_owner_filter with print_mode and nid_mask fields
- Static owner_filter instance initialized with default values
- page_owner_filter debugfs directory

The filter infrastructure will be used to add print_mode and NUMA node
filtering capabilities in subsequent commits.

Link: https://lore.kernel.org/20260419155540.376847-1-zhen.ni@easystack.cn
Link: https://lore.kernel.org/linux-mm/20260417154638.22370-2-zhen.ni@easystack.cn/
Link: https://lore.kernel.org/20260419155540.376847-2-zhen.ni@easystack.cn
Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
Suggested-by: Zi Yan <ziy@nvidia.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_owner.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

--- a/mm/page_owner.c~mm-page_owner-add-filter-infrastructure
+++ a/mm/page_owner.c
@@ -54,6 +54,21 @@ struct stack_print_ctx {
 	u8 flags;
 };
 
+enum page_owner_print_mode {
+	PAGE_OWNER_PRINT_FULL_STACK,
+	PAGE_OWNER_PRINT_STACK_HANDLE,
+};
+
+struct page_owner_filter {
+	enum page_owner_print_mode print_mode;
+	nodemask_t nid_mask;
+};
+
+static struct page_owner_filter owner_filter = {
+	.print_mode = PAGE_OWNER_PRINT_FULL_STACK,
+	.nid_mask = NODE_MASK_NONE,
+};
+
 static bool page_owner_enabled __initdata;
 DEFINE_STATIC_KEY_FALSE(page_owner_inited);
 
@@ -973,7 +988,7 @@ DEFINE_SIMPLE_ATTRIBUTE(page_owner_thres
 
 static int __init pageowner_init(void)
 {
-	struct dentry *dir;
+	struct dentry *dir, *filter_dir;
 
 	if (!static_branch_unlikely(&page_owner_inited)) {
 		pr_info("page_owner is disabled\n");
@@ -981,6 +996,9 @@ static int __init pageowner_init(void)
 	}
 
 	debugfs_create_file("page_owner", 0400, NULL, NULL, &page_owner_fops);
+
+	filter_dir = debugfs_create_dir("page_owner_filter", NULL);
+
 	dir = debugfs_create_dir("page_owner_stacks", NULL);
 	debugfs_create_file("show_stacks", 0400, dir,
 			    (void *)(STACK_PRINT_FLAG_STACK |
_

Patches currently in -mm which might be from zhen.ni@easystack.cn are

mm-page_owner-add-print_mode-filter.patch
mm-page_owner-add-numa-node-filter-with-nodelist-support.patch
mm-page_owner-fix-%pgp-format-specifier-argument-type.patch