On 2022/3/1 7:57, Yang Shi wrote:
> The DAX vma may be seen by khugepaged when the mm has other khugepaged
> suitable vmas. So khugepaged may try to collapse THP for DAX vma, but
> it will fail due to page sanity check, for example, page is not
> on LRU.
Yep. There is PageLRU check in khugepaged_scan_{file,pmd}.
>
> So it is not harmful, but it is definitely pointless to run khugepaged
> against DAX vma, so skip it in early check.
>
This patch looks good to me. Thanks.
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> ---
> mm/khugepaged.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 82c71c6da9ce..a0e4fa33660e 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -448,6 +448,10 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
> if (vm_flags & VM_NO_KHUGEPAGED)
> return false;
>
> + /* Don't run khugepaged against DAX vma */
> + if (vma_is_dax(vma))
> + return false;
> +
> if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
> vma->vm_pgoff, HPAGE_PMD_NR))
> return false;
>
