Re: [RFC PATCH 3/5] mm: shmem: add THP validation for PMD-mapped THP related statistics

[Barry Song <21cnbao@gmail.com>]

On Mon, Apr 22, 2024 at 3:03 PM Baolin Wang
<baolin.wang@linux.alibaba.com> wrote:
>
> In order to extend support for mTHP, add THP validation for PMD-mapped THP
> related statistics to avoid statistical confusion.
>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---

Reviewed-by: Barry  Song <v-songbaohua@oppo.com>

>  mm/shmem.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 893c88efc45f..b4afda71a3f0 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1662,7 +1662,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
>                         return ERR_PTR(-E2BIG);
>
>                 folio = shmem_alloc_hugefolio(gfp, info, index, order);
> -               if (!folio)
> +               if (!folio && pages == HPAGE_PMD_NR)
>                         count_vm_event(THP_FILE_FALLBACK);
>         } else {
>                 pages = 1;
> @@ -1680,7 +1680,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
>                 if (xa_find(&mapping->i_pages, &index,
>                                 index + pages - 1, XA_PRESENT)) {
>                         error = -EEXIST;
> -               } else if (huge) {
> +               } else if (pages == HPAGE_PMD_NR) {
>                         count_vm_event(THP_FILE_FALLBACK);
>                         count_vm_event(THP_FILE_FALLBACK_CHARGE);
>                 }
> @@ -2046,7 +2046,8 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
>                 folio = shmem_alloc_and_add_folio(huge_gfp,
>                                 inode, index, fault_mm, true);
>                 if (!IS_ERR(folio)) {
> -                       count_vm_event(THP_FILE_ALLOC);
> +                       if (folio_test_pmd_mappable(folio))
> +                               count_vm_event(THP_FILE_ALLOC);
>                         goto alloced;
>                 }
>                 if (PTR_ERR(folio) == -EEXIST)
> --
> 2.39.3
>