Re: [PATCH v1 1/3] selftests/mm: Fix half_ufd_size_MB calculation

[Peter Xu <peterx@redhat.com>]

On Tue, Mar 18, 2025 at 05:43:39PM +0000, Ryan Roberts wrote:
> $half_ufd_size_MB is supposed to be half of the available hugetlb memory
> expressed in MB. But previously it was calculated in pages since
> $freepgs is the number of free pages.
> 
> When huge pages are 2M it doesn't make a whole lot of difference; the
> number of pages that get used is just halved. But on arm64 with 16K or
> 64K base pages, the PMD size (and default hugetlb size) is 32M and 512M
> respectively. So in this case we end up passing a number of MB that is
> smaller than a single hugetlb page and the test raises an error.
> 
> Fixes: 2e47a445d7b3 ("selftests/mm: run_vmtests.sh: fix hugetlb mem size calculation")
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

There's a similar fix already in akpm/mm-hotfixes-stable:

67a2f86846f2 selftests/mm: run_vmtests.sh: fix half_ufd_size_MB calculation

Thanks,

> ---
>  tools/testing/selftests/mm/run_vmtests.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index da7e26668103..14fa9d40d574 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -304,7 +304,7 @@ uffd_stress_bin=./uffd-stress
>  CATEGORY="userfaultfd" run_test ${uffd_stress_bin} anon 20 16
>  # Hugetlb tests require source and destination huge pages. Pass in half
>  # the size of the free pages we have, which is used for *each*.
> -half_ufd_size_MB=$((freepgs / 2))
> +half_ufd_size_MB=$(((freepgs * hpgsize_KB / 2) / 1024))
>  CATEGORY="userfaultfd" run_test ${uffd_stress_bin} hugetlb "$half_ufd_size_MB" 32
>  CATEGORY="userfaultfd" run_test ${uffd_stress_bin} hugetlb-private "$half_ufd_size_MB" 32
>  CATEGORY="userfaultfd" run_test ${uffd_stress_bin} shmem 20 16
> --
> 2.43.0
> 

-- 
Peter Xu