[PATCH v4 1/2] mm: hugetlb_vmemmap: introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP

[Barry Song]

On Thu, Mar 31, 2022 at 7:57 PM Muchun Song <songmuchun at bytedance.com> wrote:
>
> The feature of minimizing overhead of struct page associated with each
> HugeTLB page is implemented on x86_64, however, the infrastructure of
> this feature is already there, we could easily enable it for other
> architectures.  Introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP for other
> architectures to be easily enabled.  Just select this config if they
> want to enable this feature.
>
> Suggested-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Muchun Song <songmuchun at bytedance.com>

Review-by: Barry Song <baohua at kernel.org>

> ---
>  arch/x86/Kconfig |  1 +
>  fs/Kconfig       | 10 +++++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 9f5bd41bf660..e69d42528542 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -119,6 +119,7 @@ config X86
>         select ARCH_WANTS_DYNAMIC_TASK_STRUCT
>         select ARCH_WANTS_NO_INSTR
>         select ARCH_WANT_HUGE_PMD_SHARE
> +       select ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP      if X86_64
>         select ARCH_WANT_LD_ORPHAN_WARN
>         select ARCH_WANTS_THP_SWAP              if X86_64
>         select ARCH_HAS_PARANOID_L1D_FLUSH
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 6c7dc1387beb..f6db2af33738 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -245,9 +245,17 @@ config HUGETLBFS
>  config HUGETLB_PAGE
>         def_bool HUGETLBFS
>
> +#
> +# Select this config option from the architecture Kconfig, if it is preferred
> +# to enable the feature of minimizing overhead of struct page associated with
> +# each HugeTLB page.
> +#
> +config ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
> +       bool
> +
>  config HUGETLB_PAGE_FREE_VMEMMAP
>         def_bool HUGETLB_PAGE
> -       depends on X86_64
> +       depends on ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
>         depends on SPARSEMEM_VMEMMAP
>
>  config HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON
> --
> 2.11.0
>