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    Subject[PATCH 10/63] mm: Do not flush TLB during protection change if !pte_present && !migration_entry
    Date
    NUMA PTE scanning is expensive both in terms of the scanning itself and
    the TLB flush if there are any updates. Currently non-present PTEs are
    accounted for as an update and incurring a TLB flush where it is only
    necessary for anonymous migration entries. This patch addresses the
    problem and should reduce TLB flushes.

    Signed-off-by: Mel Gorman <mgorman@suse.de>
    ---
    mm/mprotect.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/mm/mprotect.c b/mm/mprotect.c
    index 2bbb648..7bdbd4b 100644
    --- a/mm/mprotect.c
    +++ b/mm/mprotect.c
    @@ -101,8 +101,9 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
    make_migration_entry_read(&entry);
    set_pte_at(mm, addr, pte,
    swp_entry_to_pte(entry));
    +
    + pages++;
    }
    - pages++;
    }
    } while (pte++, addr += PAGE_SIZE, addr != end);
    arch_leave_lazy_mmu_mode();
    --
    1.8.4


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