Hi Baolin,

On Mon, 20 Jun 2022 10:34:42 +0800 Baolin Wang baolin.wang@linux.alibaba.com 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@arm.com/

Fixes: 49f4203aae06 ("mm/damon: add access checking for hugetlb pages")

As the commit has merged in from v5.17, I guess it would be better to do below?

Cc: stable@vger.kernel.org

Signed-off-by: Baolin Wang baolin.wang@linux.alibaba.com

Other than that,

Reviewed-by: SeongJae Park sj@kernel.org

Thanks, SJ

---

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