> We could go one step further and special case in mm_get_huge_zero_folio() +
> mm_put_huge_zero_folio() on CONFIG_STATIC_HUGE_ZERO_FOLIO.
>
Hmm, but we could have also failed to allocate even though the option
was enabled.
2 options:
- we could do:
if (IS_ENABLED(CONFIG_STATIC_HUGE_ZERO_FOLIO) && huge_zero_folio)
return huge_zero_folio;
or
- As dave suggested, we could do a static key and enable it when the
option is enabled and the allocation succeeded. The same static key
can also be used in get_static_huge_zero_folio().
I think the latter option will look more clean and slightly more
optimal?
> Something like
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 9c38a95e9f091..9b87884e5f299 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -248,6 +248,9 @@ static void put_huge_zero_page(void)
>
> struct folio *mm_get_huge_zero_folio(struct mm_struct *mm)
> {
> + if (IS_ENABLED(CONFIG_STATIC_HUGE_ZERO_FOLIO))
> + return huge_zero_folio;
> +
> if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
> return READ_ONCE(huge_zero_folio);
>
> @@ -262,6 +265,9 @@ struct folio *mm_get_huge_zero_folio(struct mm_struct
> *mm)
>
> void mm_put_huge_zero_folio(struct mm_struct *mm)
> {
> + if (IS_ENABLED(CONFIG_STATIC_HUGE_ZERO_FOLIO))
> + return huge_zero_folio;
> +
> if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
> put_huge_zero_page();
> }
>
--
Pankaj
