Le 18/07/2024 à 00:02, Peter Xu a écrit :
> Introduce two more sub-options for PGTABLE_HAS_HUGE_LEAVES:
>
> - PGTABLE_HAS_PMD_LEAVES: set when there can be PMD mappings
> - PGTABLE_HAS_PUD_LEAVES: set when there can be PUD mappings
>
> It will help to identify whether the current build may only want PMD
> helpers but not PUD ones, as these sub-options will also check against the
> arch support over HAVE_ARCH_TRANSPARENT_HUGEPAGE[_PUD].
>
> Note that having them depend on HAVE_ARCH_TRANSPARENT_HUGEPAGE[_PUD] is
> still some intermediate step. The best way is to have an option say
> "whether arch XXX supports PMD/PUD mappings" and so on. However let's
> leave that for later as that's the easy part. So far, we use these options
> to stably detect per-arch huge mapping support.
>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> ---
> include/linux/huge_mm.h | 10 +++++++---
> mm/Kconfig | 6 ++++++
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 711632df7edf..37482c8445d1 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -96,14 +96,18 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr;
> #define thp_vma_allowable_order(vma, vm_flags, tva_flags, order) \
> (!!thp_vma_allowable_orders(vma, vm_flags, tva_flags, BIT(order)))
>
> -#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
> -#define HPAGE_PMD_SHIFT PMD_SHIFT
> +#ifdef CONFIG_PGTABLE_HAS_PUD_LEAVES
> #define HPAGE_PUD_SHIFT PUD_SHIFT
> #else
> -#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
> #define HPAGE_PUD_SHIFT ({ BUILD_BUG(); 0; })
> #endif
>
> +#ifdef CONFIG_PGTABLE_HAS_PMD_LEAVES
> +#define HPAGE_PMD_SHIFT PMD_SHIFT
> +#else
> +#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
> +#endif
> +
> #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
> #define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
> #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 60796402850e..2dbdc088dee8 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -860,6 +860,12 @@ endif # TRANSPARENT_HUGEPAGE
> config PGTABLE_HAS_HUGE_LEAVES
> def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE
>
> +config PGTABLE_HAS_PMD_LEAVES
> + def_bool HAVE_ARCH_TRANSPARENT_HUGEPAGE && PGTABLE_HAS_HUGE_LEAVES
> +
> +config PGTABLE_HAS_PUD_LEAVES
> + def_bool HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD && PGTABLE_HAS_HUGE_LEAVES
> +
What if an architecture has hugepages at PMD and/or PUD level and
doesn't support THP ?
Christophe
> #
> # UP and nommu archs use km based percpu allocator
> #
