Re: [PATCH] mm/damon: Use set_huge_pte_at() to make huge pte old

From: Mike Kravetz
Date: Tue Jun 21 2022 - 19:42:15 EST


On 06/20/22 10:34, Baolin Wang wrote:
> The huge_ptep_set_access_flags() can not make the huge pte old according
> to the discussion [1], that means we will always mornitor the young state
> of the hugetlb though we stopped accessing the hugetlb, as a result DAMON
> will get inaccurate accessing statistics.
>
> So changing to use set_huge_pte_at() to make the huge pte old to fix this
> issue.
>
> [1] https://lore.kernel.org/all/Yqy97gXI4Nqb7dYo@xxxxxxx/
>
> Fixes: 49f4203aae06 ("mm/damon: add access checking for hugetlb pages")
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Thanks,

Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
--
Mike Kravetz

> ---
> mm/damon/vaddr.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 5767be72c181..d24148a8149f 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -337,8 +337,7 @@ static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
> if (pte_young(entry)) {
> referenced = true;
> entry = pte_mkold(entry);
> - huge_ptep_set_access_flags(vma, addr, pte, entry,
> - vma->vm_flags & VM_WRITE);
> + set_huge_pte_at(mm, addr, pte, entry);
> }
>
> #ifdef CONFIG_MMU_NOTIFIER
> --
> 2.27.0
>