Re: [PATCH v5 6/7] selftests: prctl: introduce tests for disabling THPs completely

[Usama Arif]

On 15/08/2025 14:54, Usama Arif wrote:
> The test will set the global system THP setting to never, madvise
> or always depending on the fixture variant and the 2M setting to
> inherit before it starts (and reset to original at teardown).
> The fixture setup will also test if PR_SET_THP_DISABLE prctl call can
> be made to disable all THPs and skip if it fails.
> 
> This tests if the process can:
> - successfully get the policy to disable THPs completely.
> - never get a hugepage when the THPs are completely disabled
>   with the prctl, including with MADV_HUGE and MADV_COLLAPSE.
> - successfully reset the policy of the process.
> - after reset, only get hugepages with:
>   - MADV_COLLAPSE when policy is set to never.
>   - MADV_HUGE and MADV_COLLAPSE when policy is set to madvise.
>   - always when policy is set to "always".
> - never get a THP with MADV_NOHUGEPAGE.
> - repeat the above tests in a forked process to make sure
>   the policy is carried across forks.
> 
> Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
>  tools/testing/selftests/mm/.gitignore         |   1 +
>  tools/testing/selftests/mm/Makefile           |   1 +
>  .../testing/selftests/mm/prctl_thp_disable.c  | 175 ++++++++++++++++++
>  tools/testing/selftests/mm/thp_settings.c     |   9 +-
>  tools/testing/selftests/mm/thp_settings.h     |   1 +
>  5 files changed, 186 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/mm/prctl_thp_disable.c
>

Andrew, could you please apply the below fixlet on top of this patch as suggested
by David in https://lore.kernel.org/all/a385e09f-f582-4ede-9e60-1d85cee02a3c@xxxxxxxxxx/?

Thanks!