Re: [PATCH 3/8] mm: khugepaged: skip DAX vma
From: Miaohe Lin <linmiaohe@huawei.com>
Date: 2022-03-02 03:21:13
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linux-fsdevel, linux-mm, linux-xfs, lkml
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@huawei.com>
quoted hunk ↗ jump to hunk
Signed-off-by: Yang Shi <redacted> --- 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;