Re: [PATCH v12 1/4] mm/page_owner: add print_mode filter

[Zi Yan <ziy@nvidia.com>]

On 7 Jul 2026, at 11:31, Zi Yan wrote:

> On 7 Jul 2026, at 11:27, Vlastimil Babka (SUSE) wrote:
>
>> On 7/7/26 13:54, Zhen Ni wrote:
>>> 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.
>>>
>>> Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
>>> Tested-by: Zi Yan <ziy@nvidia.com>
>>
>> I think in general Tested-by" can't carry from previous version due to
>> (functional) changes. Andrew can remove it locally, or Zi can re-test :)
>
> Let me do a quick retest. :)
>

Everything works as expected as I just tested the code using the supplied
userspace tool. I also discovered a small typo in Patch 2. ;)

1. I used the tool manual with NUMA filter + handle|stack|stack_handle.
2. I also used the script from the cover letter and checked the output.

Tested-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi