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

[Vlastimil Babka (SUSE)]

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@xxxxxxxxxxxx>
> Tested-by: Zi Yan <ziy@xxxxxxxxxx>

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 :)

> Acked-by: Zi Yan <ziy@xxxxxxxxxx>

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>