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

[Ryan Roberts <ryan.roberts@arm.com>]

On 18/03/2025 19:54, Peter Xu wrote:
> 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

Oops, my bad, forgot to check mm branches. This was just a drive-by fix while
working in another context.

Hopefully Andrew is ok to take the other 2 patches and drop this one? If not,
let me know and I'll resend the two other patches on their own.

Thanks,
Ryan

> 
> 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
>>
>