diff mbox series

[v3,3/8] mm: khugepaged: skip DAX vma

Message ID 20220404200250.321455-4-shy828301@gmail.com (mailing list archive)
State New, archived
Headers show
Series Make khugepaged collapse readonly FS THP more consistent | expand

Commit Message

Yang Shi April 4, 2022, 8:02 p.m. UTC 
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.

So it is not harmful, but it is definitely pointless to run khugepaged
against DAX vma, so skip it in early check.

Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 mm/khugepaged.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Vlastimil Babka May 9, 2022, 12:46 p.m. UTC | #1 
On 4/4/22 22:02, 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.
> 
> So it is not harmful, but it is definitely pointless to run khugepaged
> against DAX vma, so skip it in early check.
> 
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> Acked-by: Song Liu <song@kernel.org>
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/khugepaged.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 7d197d9e3258..964a4d2c942a 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -447,6 +447,10 @@ 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;
diff mbox series

Patch

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 7d197d9e3258..964a4d2c942a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -447,6 +447,10 @@  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;