Re: [PATCH v3 2/4] mm: Default implementation of arch_wants_pte_order()
From: Yin Fengwei <hidden>
Date: 2023-07-17 11:13:38
Also in:
linux-mm, lkml
On 7/15/23 00:17, 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 -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@arm.com>
Reviewed-by: Yin Fengwei <redacted> Regards Yin, Fengwei
quoted hunk ↗ jump to hunk
--- include/linux/pgtable.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 5063b482e34f..2a1d83775837 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h@@ -313,6 +313,19 @@ 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. Negative value implies that the HW has no preference + * and mm will choose it's own default order. + */ +static inline int arch_wants_pte_order(void) +{ + return -1; +} +#endif + #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long address,
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