Re: [PATCH] smaps: count large pages smaller than PMD size to anonymous_thp

[David Hildenbrand <david@redhat.com>]

On 03.12.24 14:49, Wenchao Hao wrote:
> Currently, /proc/xxx/smaps reports the size of anonymous huge pages for
> each VMA, but it does not include large pages smaller than PMD size.
> 
> This patch adds the statistics of anonymous huge pages allocated by
> mTHP which is smaller than PMD size to AnonHugePages field in smaps.
> 
> Signed-off-by: Wenchao Hao <haowenchao22@gmail.com>
> ---
>   fs/proc/task_mmu.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 38a5a3e9cba2..b655011627d8 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -717,6 +717,12 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
>   		if (!folio_test_swapbacked(folio) && !dirty &&
>   		    !folio_test_dirty(folio))
>   			mss->lazyfree += size;
> +
> +		/*
> +		 * Count large pages smaller than PMD size to anonymous_thp
> +		 */
> +		if (!compound && PageHead(page) && folio_order(folio))
> +			mss->anonymous_thp += folio_size(folio);
>   	}
>   
>   	if (folio_test_ksm(folio))


I think we decided to leave this (and /proc/meminfo) be one of the last
interfaces where this is only concerned with PMD-sized ones:

Documentation/admin-guide/mm/transhuge.rst:

The number of PMD-sized anonymous transparent huge pages currently used by the
system is available by reading the AnonHugePages field in ``/proc/meminfo``.
To identify what applications are using PMD-sized anonymous transparent huge
pages, it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages
fields for each mapping. (Note that AnonHugePages only applies to traditional
PMD-sized THP for historical reasons and should have been called
AnonHugePmdMapped).



-- 
Cheers,

David / dhildenb