[PATCH v1 10/10] mm: Allocate large folios for anonymous memory

[Yu Zhao]

On Mon, Jun 26, 2023 at 11:15 AM Ryan Roberts <ryan.roberts at arm.com> wrote:
>
> With all of the enabler patches in place, modify the anonymous memory
> write allocation path so that it opportunistically attempts to allocate
> a large folio up to `max_anon_folio_order()` size (This value is
> ultimately configured by the architecture). This reduces the number of
> page faults, reduces the size of (e.g. LRU) lists, and generally
> improves performance by batching what were per-page operations into
> per-(large)-folio operations.
>
> If CONFIG_LARGE_ANON_FOLIO is not enabled (the default) then
> `max_anon_folio_order()` always returns 0, meaning we get the existing
> allocation behaviour.
>
> Signed-off-by: Ryan Roberts <ryan.roberts at arm.com>
> ---
>  mm/memory.c | 159 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 144 insertions(+), 15 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index a8f7e2b28d7a..d23c44cc5092 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3161,6 +3161,90 @@ static inline int max_anon_folio_order(struct vm_area_struct *vma)
>                 return CONFIG_LARGE_ANON_FOLIO_NOTHP_ORDER_MAX;
>  }
>
> +/*
> + * Returns index of first pte that is not none, or nr if all are none.
> + */
> +static inline int check_ptes_none(pte_t *pte, int nr)
> +{
> +       int i;
> +
> +       for (i = 0; i < nr; i++) {
> +               if (!pte_none(ptep_get(pte++)))
> +                       return i;
> +       }
> +
> +       return nr;
> +}
> +
> +static int calc_anon_folio_order_alloc(struct vm_fault *vmf, int order)

As suggested previously in 03/10, we can leave this for later.