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    SubjectRe: [PATCH] mm/hugetlb: avoid looping to the same hugepage if !pages and !vmas
    On Thu, Aug 29, 2019 at 07:37:22PM +0800, zhigang lu wrote:
    > This change greatly decrease the time of mmaping a file in hugetlbfs.
    > With MAP_POPULATE flag, it takes about 50 milliseconds to mmap a
    > existing 128GB file in hugetlbfs. With this change, it takes less
    > then 1 millisecond.

    You're going to need to find a new way of sending patches; this patch is
    mangled by your mail system.

    > @@ -4391,6 +4391,17 @@ long follow_hugetlb_page(struct mm_struct *mm,
    > struct vm_area_struct *vma,
    > break;
    > }
    > }
    > +
    > + if (!pages && !vmas && !pfn_offset &&
    > + (vaddr + huge_page_size(h) < vma->vm_end) &&
    > + (remainder >= pages_per_huge_page(h))) {
    > + vaddr += huge_page_size(h);
    > + remainder -= pages_per_huge_page(h);
    > + i += pages_per_huge_page(h);
    > + spin_unlock(ptl);
    > + continue;
    > + }

    The concept seems good to me. The description above could do with some
    better explanation though.

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