Re: [PATCH v2 1/4] mm: avoid unnecessary lru drain for wp_can_reuse_anon_folio()

[Kairui Song <ryncsn@gmail.com>]

On Wed, Jun 24, 2026 at 7:16 AM Barry Song (Xiaomi) <baohua@kernel.org> wrote:
>
> We always unconditionally drain the LRU before retrying anon folio
> reuse in wp_can_reuse_anon_folio(). Instead, assume !LRU anon folios
> are in lru_cache, and use the refcount to avoid many unnecessary LRU
> drains.
>
> Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
> Reviewed-by: Baoquan He <baoquan.he@linux.dev>
> Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
> ---
>  mm/memory.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index ff338c2abe92..f6848f4234a6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4193,12 +4193,18 @@ static bool wp_can_reuse_anon_folio(struct folio *folio,
>          */
>         if (folio_test_ksm(folio) || folio_ref_count(folio) > 3)
>                 return false;
> -       if (!folio_test_lru(folio))
> +       if (!folio_test_lru(folio)) {
> +               /*
> +                * Assume folio is on lru_cache and holds a cache reference.
> +                */
> +               if (folio_ref_count(folio) > 2 + folio_test_swapcache(folio))
> +                       return false;
>                 /*
>                  * We cannot easily detect+handle references from
>                  * remote LRU caches or references to LRU folios.
>                  */
>                 lru_add_drain();
> +       }
>         if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio))
>                 return false;
>         if (!folio_trylock(folio))
> --
> 2.39.3 (Apple Git-146)
>

Reviewed-by: Kairui Song <kasong@tencent.com>