Re: [PATCH] selftests/mm: run_vmtests.sh: fix half_ufd_size_MB calculation

[David Hildenbrand <david@redhat.com>]

On 18.02.25 20:22, Rafael Aquini wrote:
> From: Rafael Aquini <raquini@redhat.com>
> 
> We noticed that uffd-stress test was always failing to run when invoked
> for the hugetlb profiles on x86_64 systems with a processor count of 64
> or bigger:
>    ...
>    # ------------------------------------
>    # running ./uffd-stress hugetlb 128 32
>    # ------------------------------------
>    # ERROR: invalid MiB (errno=9, @uffd-stress.c:459)
>    ...
>    # [FAIL]
>    not ok 3 uffd-stress hugetlb 128 32 # exit=1
>    ...
> 
> The problem boils down to how run_vmtests.sh (mis)calculates the size
> of the region it feeds to uffd-stress. The latter expects to see an
> amount of MiB while the former is just giving out the number of free
> hugepages halved down. This measurement discrepancy ends up violating
> uffd-stress' assertion on number of hugetlb pages allocated per CPU,
> causing it to bail out with the error above.
> 
> This commit fixes that issue by adjusting run_vmtests.sh's half_ufd_size_MB
> calculation so it properly renders the region size in MiB, as expected,
> while maintaining all of its original constraints in place.
> 
> Fixes: 2e47a445d7b3 ("selftests/mm: run_vmtests.sh: fix hugetlb mem size calculation")
> Signed-off-by: Rafael Aquini <raquini@redhat.com>
> ---
>   tools/testing/selftests/mm/run_vmtests.sh | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index 333c468c2699..157d07e5aaa3 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -304,7 +304,9 @@ 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))
> +# uffd-stress expects a region expressed in MiB, so we adjust
> +# half_ufd_size_MB accordingly.
> +half_ufd_size_MB=$(((freepgs * hpgsize_KB) / 1024 / 2))

LGTM

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb