Re: [PATCH 2/3] mm/page_owner: add compact mode filter

[Zi Yan]

On 17 Apr 2026, at 11:46, Zhen Ni wrote:

> Add compact mode functionality to reduce page_owner output size by
> printing only the stack handle instead of the full stack trace.

Maybe you could add an enum type for what content is printed.
Something like PAGE_OWNER_PRINT_STACK_HANDLE and PAGE_OWNER_PRINT_FULL_STACK.
Since compact is a very vague name for what the code does.

For the sysfs interface, stack_handle vs full_stack would be used.

>
> Example output:
>   Page allocated via order 0, mask 0x42800(GFP_NOWAIT|__GFP_COMP),
>   pid 1, tgid 1 (systemd), ts 349667370 ns
>   PFN 0xa00a2 type Unmovable Block 1280 type Unmovable
>   Flags 0x33fffe0000004124(referenced|lru|active|private|node=3|zone=0|
> lastcpupid=0x1ffff)
>   handle: 17432583
>   Charged to memcg /
>
> Compact mode significantly reduces output size while preserving all
> other page allocation information, making it easier to analyze large
> volumes of page owner data.The correspondence between handles and stack
> traces can be obtained through the show_stacks_handles interface.
>
> Signed-off-by: Zhen Ni <zhen.ni@xxxxxxxxxxxx>
> ---
>  mm/page_owner.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 6811439bf9e4..214b58eef3d8 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -585,7 +585,14 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>  			migratetype_names[pageblock_mt],
>  			&page->flags);
>
> -	ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
> +	/* Compact mode: print handle instead of full stack trace */
> +	if (READ_ONCE(owner_filter.compact)) {
> +		ret += scnprintf(kbuf + ret, count - ret,
> +				"handle: %d\n", handle);
> +	} else {
> +		ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
> +	}
> +
>  	if (ret >= count)
>  		goto err;
>
> @@ -980,6 +987,24 @@ static int page_owner_threshold_set(void *data, u64 val)
>  DEFINE_SIMPLE_ATTRIBUTE(page_owner_threshold_fops, &page_owner_threshold_get,
>  			&page_owner_threshold_set, "%llu");
>
> +static int page_owner_compact_get(void *data, u64 *val)
> +{
> +	*val = READ_ONCE(owner_filter.compact);
> +	return 0;
> +}
> +
> +static int page_owner_compact_set(void *data, u64 val)
> +{
> +	if (val != 0 && val != 1)
> +		return -EINVAL;
> +	WRITE_ONCE(owner_filter.compact, val);
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(page_owner_compact_fops,
> +			&page_owner_compact_get,
> +			&page_owner_compact_set, "%lld");
> +
>
>  static int __init pageowner_init(void)
>  {
> @@ -993,6 +1018,8 @@ 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);
> +	debugfs_create_file("compact", 0600, filter_dir, NULL,
> +			    &page_owner_compact_fops);
>
>  	dir = debugfs_create_dir("page_owner_stacks", NULL);
>  	debugfs_create_file("show_stacks", 0400, dir,
> -- 
> 2.20.1


Best Regards,
Yan, Zi