Re: [PATCH v3 2/4] mm: Default implementation of arch_wants_pte_order()

[Yu Zhao]

On Fri, Jul 14, 2023 at 10:17 AM Ryan Roberts <ryan.roberts@xxxxxxx> wrote:
>
> arch_wants_pte_order() can be overridden by the arch to return the
> preferred folio order for pte-mapped memory. This is useful as some
> architectures (e.g. arm64) can coalesce TLB entries when the physical
> memory is suitably contiguous.
>
> The first user for this hint will be FLEXIBLE_THP, which aims to
> allocate large folios for anonymous memory to reduce page faults and
> other per-page operation costs.
>
> Here we add the default implementation of the function, used when the
> architecture does not define it, which returns -1, implying that the HW
> has no preference. In this case, mm will choose it's own default order.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>

Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>

Thanks: -1 actually is better than 0 (what I suggested) for the obvious reason.