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Patch series "mm/page_owner: add per-fd filter infrastructure for
print_mode and NUMA filtering", v12.
This patch series introduces per-file-descriptor filtering capabilities to the
page_owner feature.
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. Previously,
page_owner could not filter by NUMA node, forcing users to collect and
analyze data for all nodes.
Solution
========
This patch series introduces a per-file-descriptor 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.
The per-fd design allows multiple concurrent page_owner reads with
different filters, solving coordination issues in multi-user production
environments.
Implementation
==============
The series is structured as follows:
- Patch 1: Implement print_mode filter infrastructure
* Add file->private_data to store per-fd filter state
* Add .open, .release, and .write file operations
* Support "stack", "handle", and "stack_handle" modes via "mode=" write commands
- Patch 2: Implement NUMA node filter infrastructure
* Add nid_filter field to per-fd state
* Support flexible nodelist format via "nid=" write commands (single, multiple, ranges)
* Validate nodes and reject non-existent nodes using nodes_subset()
- Patch 3: Add page_owner_filter userspace tool
* Manages per-fd filters via write() interface
* Provides user-friendly command-line interface
* Includes comprehensive input validation
- Patch 4: Document filter features and usage
Usage Example
=============
Using the page_owner_filter tool with per-fd filters:
# ./page_owner_filter -m stack_handle -n "0,2-3" -o page_owner.txt
The tool opens /sys/kernel/debug/page_owner, sets filters via write(),
then reads the filtered output to the specified file (or stdout).
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
This patch (of 4):
Add a print_mode filter to page_owner that allows users to choose between
printing stack traces, stack handles, or both, providing flexibility for
different debugging and analysis scenarios.
The filter provides three modes via page_owner:
- Writing "mode=stack" prints stack traces for each page (default)
- Writing "mode=handle" prints only the handle number
- Writing "mode=stack_handle" prints both stack traces and handles
The default stack mode maintains backward compatibility with existing
usage, displaying complete stack traces for each page allocation.
The handle mode dramatically reduces log size and improves performance by
showing only the handle number instead of the full stack trace. Testing
shows handle mode reduces output size by ~66% (84MB vs 244MB) and improves
read performance by ~4.4x compared to full stack output. The mapping from
handles to actual stack traces can be obtained via the show_stacks_handles
interface.
The stack_handle mode prints both stack traces and handles, making it
easier to identify pages with the same allocation pattern by comparing
handle numbers instead of comparing large stack traces.
Example usage:
# Using the page_owner_filter tool (recommended)
./page_owner_filter -m stack # Print only stack traces (default)
./page_owner_filter -m handle # Print only handles
./page_owner_filter -m stack_handle # Print both stack and handles
Sample output (handle mode):
Page allocated via order 0, migratetype Unmovable, gfp_mask 0x1100ca,
pid 1, tgid 1 (systemd), ts 123456789 ns
PFN 0x1000 type Unmovable Block 1 type Unmovable
Flags 0x3fffe800000084(referenced|lru|active|private|node=0|zone=1)
handle: 17432583
...
This implementation uses per-file-descriptor filter state stored in
file->private_data, allowing each opener to have independent filter
configuration.
Link: https://lore.kernel.org/20260707115411.1714314-1-zhen.ni@easystack.cn
Link: https://lore.kernel.org/20260707115411.1714314-2-zhen.ni@easystack.cn
Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
Tested-by: Zi Yan <ziy@nvidia.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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