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    SubjectRe: [PATCH 1/4] hugetlb: skip to end of PT page mapping when pte not present
    On Thu, Jun 16, 2022 at 02:05:15PM -0700, Mike Kravetz wrote:
    > HugeTLB address ranges are linearly scanned during fork, unmap and
    > remap operations. If a non-present entry is encountered, the code
    > currently continues to the next huge page aligned address. However,
    > a non-present entry implies that the page table page for that entry
    > is not present. Therefore, the linear scan can skip to the end of
    > range mapped by the page table page. This can speed operations on
    > large sparsely populated hugetlb mappings.
    >
    > Create a new routine hugetlb_mask_last_page() that will return an
    > address mask. When the mask is ORed with an address, the result
    > will be the address of the last huge page mapped by the associated
    > page table page. Use this mask to update addresses in routines which
    > linearly scan hugetlb address ranges when a non-present pte is
    > encountered.
    >
    > hugetlb_mask_last_page is related to the implementation of
    > huge_pte_offset as hugetlb_mask_last_page is called when huge_pte_offset
    > returns NULL. This patch only provides a complete hugetlb_mask_last_page
    > implementation when CONFIG_ARCH_WANT_GENERAL_HUGETLB is defined.
    > Architectures which provide their own versions of huge_pte_offset can also
    > provide their own version of hugetlb_mask_last_page.
    >
    > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
    > Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
    > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

    It'll be more efficient, Thanks.

    Acked-by: Muchun Song <songmuchun@bytedance.com>

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