On 7/3/2023 9:53 PM, Ryan Roberts 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 the order corresponding
> to 64K.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> ---
> include/linux/pgtable.h | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index a661a17173fa..f7e38598f20b 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -13,6 +13,7 @@
> #include <linux/errno.h>
> #include <asm-generic/pgtable_uffd.h>
> #include <linux/page_table_check.h>
> +#include <linux/sizes.h>
>
> #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
> defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
> @@ -336,6 +337,18 @@ static inline bool arch_has_hw_pte_young(void)
> }
> #endif
>
> +#ifndef arch_wants_pte_order
> +/*
> + * Returns preferred folio order for pte-mapped memory. Must be in range [0,
> + * PMD_SHIFT-PAGE_SHIFT) and must not be order-1 since THP requires large folios
> + * to be at least order-2.
> + */
> +static inline int arch_wants_pte_order(struct vm_area_struct *vma)
> +{
> + return ilog2(SZ_64K >> PAGE_SHIFT);
Default value which is not related with any silicon may be: PAGE_ALLOC_COSTLY_ORDER?
Also, current pcp list support cache page with order 0...PAGE_ALLOC_COSTLY_ORDER, 9.
If the pcp could cover the page, the pressure to zone lock will be reduced by pcp.
Regards
Yin, Fengwei
> +}
> +#endif
> +
> #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
> static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> unsigned long address,
