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    SubjectRe: [PATCH 2/7] khugepaged: Do not stop collapse if less than half PTEs are referenced
    Date
    On 27 Mar 2020, at 13:05, Kirill A. Shutemov wrote:

    > __collapse_huge_page_swapin() check number of referenced PTE to decide
    > if the memory range is hot enough to justify swapin.
    >
    > The problem is that it stops collapse altogether if there's not enough
    > refereced pages, not only swappingin.
    >
    > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    > Fixes: 0db501f7a34c ("mm, thp: convert from optimistic swapin collapsing to conservative")
    > ---
    > mm/khugepaged.c | 3 ++-
    > 1 file changed, 2 insertions(+), 1 deletion(-)
    >
    > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
    > index 99bab7e4d05b..14d7afc90786 100644
    > --- a/mm/khugepaged.c
    > +++ b/mm/khugepaged.c
    > @@ -905,7 +905,8 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
    > /* we only decide to swapin, if there is enough young ptes */
    > if (referenced < HPAGE_PMD_NR/2) {
    > trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
    > - return false;
    > + /* Do not block collapse, only skip swapping in */
    > + return true;
    > }
    > vmf.pte = pte_offset_map(pmd, address);
    > for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
    > --
    > 2.26.0

    Make sense.

    Reviewed-by: Zi Yan <ziy@nvidia.com>


    Best Regards,
    Yan Zi
    [unhandled content-type:application/pgp-signature]
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