Re: [PATCH v2] mm: huge_memory: add the missing folio_test_pmd_mappable() for THP split statistics

[Lance Yang]

On Mon, Apr 22, 2024 at 3:33 PM Baolin Wang
<baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>
> Now the mTHP can also be split or added into the deferred list, so add
> folio_test_pmd_mappable() validation for PMD mapped THP, to avoid confusion
> with PMD mapped THP related statistics.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>

LGTM!

Reviewed-by: Lance Yang <ioworker0@xxxxxxxxx>

Thanks,
Lance

> ---
> Changes from v1:
>  - Add acked tag from David.
>  - Check the THP earlier in case the folio is split per Lance.
> ---
>  mm/huge_memory.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 716d29c21b6e..a9789ca823bc 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2994,6 +2994,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>         XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
>         struct anon_vma *anon_vma = NULL;
>         struct address_space *mapping = NULL;
> +       bool is_thp = folio_test_pmd_mappable(folio);
>         int extra_pins, ret;
>         pgoff_t end;
>         bool is_hzp;
> @@ -3172,7 +3173,8 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>                 i_mmap_unlock_read(mapping);
>  out:
>         xas_destroy(&xas);
> -       count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
> +       if (is_thp)
> +               count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
>         return ret;
>  }
>
> @@ -3234,7 +3236,8 @@ void deferred_split_folio(struct folio *folio)
>
>         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
>         if (list_empty(&folio->_deferred_list)) {
> -               count_vm_event(THP_DEFERRED_SPLIT_PAGE);
> +               if (folio_test_pmd_mappable(folio))
> +                       count_vm_event(THP_DEFERRED_SPLIT_PAGE);
>                 list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
>                 ds_queue->split_queue_len++;
>  #ifdef CONFIG_MEMCG
> --
> 2.39.3
>