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    SubjectRe: [PATCH] arm64/hugetlb: Implement arm64 specific hugetlb_mask_last_hp
    On 06/16/22 at 11:34am, Baolin Wang wrote:
    > The HugeTLB address ranges are linearly scanned during fork, unmap and
    > remap operations, and the linear scan can skip to the end of range mapped
    > by the page table page if hitting a non-present entry, which can help
    > to speed linear scanning of the HugeTLB address ranges.
    >
    > So hugetlb_mask_last_hp() is introduced to help to update the address in
    > the loop of HugeTLB linear scanning with getting the last huge page mapped
    > by the associated page table page[1], when a non-present entry is encountered.
    >
    > Considering ARM64 specific cont-pte/pmd size HugeTLB, this patch implemented
    > an ARM64 specific hugetlb_mask_last_hp() to help this case.
    >
    > [1] https://lore.kernel.org/linux-mm/20220527225849.284839-1-mike.kravetz@oracle.com/
    >
    > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
    > ---
    > Note: this patch is based on the series: "hugetlb: speed up linear
    > address scanning" from Mike. Mike, please fold it into your series.
    > Thanks.
    > ---
    > arch/arm64/mm/hugetlbpage.c | 20 ++++++++++++++++++++
    > 1 file changed, 20 insertions(+)
    >
    > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
    > index e2a5ec9..958935c 100644
    > --- a/arch/arm64/mm/hugetlbpage.c
    > +++ b/arch/arm64/mm/hugetlbpage.c
    > @@ -368,6 +368,26 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
    > return NULL;
    > }
    >
    > +unsigned long hugetlb_mask_last_hp(struct hstate *h)
    > +{
    > + unsigned long hp_size = huge_page_size(h);

    hp_size may not be a good name, it reminds me of hotplug. I would name
    it hpage_size even though a little more characters are added.

    > +
    > + switch (hp_size) {
    > + case PUD_SIZE:
    > + return PGDIR_SIZE - PUD_SIZE;
    > + case CONT_PMD_SIZE:
    > + return PUD_SIZE - CONT_PMD_SIZE;
    > + case PMD_SIZE:
    > + return PUD_SIZE - PMD_SIZE;
    > + case CONT_PTE_SIZE:
    > + return PMD_SIZE - CONT_PTE_SIZE;
    > + default:
    > + break;
    > + }
    > +
    > + return ~0UL;
    > +}
    > +
    > pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
    > {
    > size_t pagesize = 1UL << shift;
    > --
    > 1.8.3.1
    >
    >

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