On 11 Jun 2025, at 23:54, Baolin Wang wrote:
> When running the khugepaged selftest for shmem (./khugepaged all:shmem),
> I encountered the following test failures:
> "
> Run test: collapse_full (khugepaged:shmem)
> Collapse multiple fully populated PTE table.... Fail
> ...
> Run test: collapse_single_pte_entry (khugepaged:shmem)
> Collapse PTE table with single PTE entry present.... Fail
> ...
> Run test: collapse_full_of_compound (khugepaged:shmem)
> Allocate huge page... OK
> Split huge page leaving single PTE page table full of compound pages... OK
> Collapse PTE table full of compound pages.... Fail
> "
>
> The reason for the failure is that, it will set MADV_NOHUGEPAGE to prevent
> khugepaged from continuing to scan shmem VMA after khugepaged finishes
> scanning in the wait_for_scan() function. Moreover, shmem requires a refault
> to establish PMD mappings.
>
> However, after commit 2b0f922323cc, PMD mappings are prevented if the VMA is
Can you add the title of the commit? It is easier to understand the context.
2b0f922323cc ("mm: don't install PMD mappings when THPs are disabled by the
hw/process/vma")
> set with MADV_NOHUGEPAGE flag, so shmem cannot establish PMD mappings during
> refault.
>
> To fix this issue, we can set the MADV_NOHUGEPAGE flag after the shmem
> refault.
> With this fix, the shmem test case passes.
>
> Fixes: 2b0f922323cc ("mm: don't install PMD mappings when THPs are disabled
> by the hw/process/vma")
> Signed-off-by: Baolin Wang <baolin.w...@linux.alibaba.com>
> ---
> tools/testing/selftests/mm/khugepaged.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/khugepaged.c
> b/tools/testing/selftests/mm/khugepaged.c
> index 8a4d34cce36b..d462f62d8116 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -561,8 +561,6 @@ static bool wait_for_scan(const char *msg, char *p, int
> nr_hpages,
> usleep(TICK);
> }
>
> - madvise(p, nr_hpages * hpage_pmd_size, MADV_NOHUGEPAGE);
> -
> return timeout == -1;
> }
>
I assume you are going to just remove this madvise based on your discussion
with David. With that, feel free to add Reviewed-by: Zi Yan <z...@nvidia.com>
Thanks.
Best Regards,
Yan, Zi
