On Fri, 25 Jul 2025 17:22:44 +0100 Usama Arif <usamaarif642@xxxxxxxxx> wrote:
> The test will set the global system THP setting to always and
> the 2M setting to inherit before it starts (and reset to original
> at teardown)
>
> This tests if the process can:
> - successfully set and get the policy to disable THPs expect for madvise.
s/expect/except/
> - get hugepages only on MADV_HUGE and MADV_COLLAPSE after policy is set.
> - successfully reset the policy of the process.
> - get hugepages always after reset.
> - repeat the above tests in a forked process to make sure the policy is
> carried across forks.
>
> Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
> ---
> .../testing/selftests/mm/prctl_thp_disable.c | 95 +++++++++++++++++++
> 1 file changed, 95 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/prctl_thp_disable.c b/tools/testing/selftests/mm/prctl_thp_disable.c
> index 52f7e6659b1f..288d5ad6ffbb 100644
> --- a/tools/testing/selftests/mm/prctl_thp_disable.c
> +++ b/tools/testing/selftests/mm/prctl_thp_disable.c
> @@ -65,6 +65,101 @@ static int test_mmap_thp(enum madvise_buffer madvise_buf, size_t pmdsize)
> munmap(buffer, buf_size);
> return ret;
> }
> +
> +FIXTURE(prctl_thp_disable_except_madvise)
> +{
> + struct thp_settings settings;
> + size_t pmdsize;
> +};
> +
> +FIXTURE_SETUP(prctl_thp_disable_except_madvise)
> +{
> + if (!thp_is_enabled())
> + SKIP(return, "Transparent Hugepages not available\n");
As David also pointed out on the other patch, the message and the function name
would better to be consistent.
> +
> + self->pmdsize = read_pmd_pagesize();
> + if (!self->pmdsize)
> + SKIP(return, "Unable to read PMD size\n");
> +
> + thp_read_settings(&self->settings);
> + self->settings.thp_enabled = THP_ALWAYS;
> + self->settings.hugepages[sz2ord(self->pmdsize, getpagesize())].enabled = THP_INHERIT;
> + thp_save_settings();
> + thp_push_settings(&self->settings);
> +
Unnecessary empty line?
> +}
> +
> +FIXTURE_TEARDOWN(prctl_thp_disable_except_madvise)
> +{
> + thp_restore_settings();
> +}
> +
> +/* prctl_thp_disable_except_madvise fixture sets system THP setting to always */
> +static void prctl_thp_disable_except_madvise(struct __test_metadata *const _metadata,
> + size_t pmdsize)
> +{
> + int res = 0;
> +
> + res = prctl(PR_GET_THP_DISABLE, NULL, NULL, NULL, NULL);
> + ASSERT_EQ(res, 3);
> +
> + /* global = always, process = madvise, we shouldn't get HPs without madvise */
> + res = test_mmap_thp(NONE, pmdsize);
> + ASSERT_EQ(res, 0);
> +
> + res = test_mmap_thp(HUGE, pmdsize);
> + ASSERT_EQ(res, 1);
> +
> + res = test_mmap_thp(COLLAPSE, pmdsize);
> + ASSERT_EQ(res, 1);
> +
> + /* Reset to system policy */
> + res = prctl(PR_SET_THP_DISABLE, 0, NULL, NULL, NULL);
> + ASSERT_EQ(res, 0);
> +
> + /* global = always, hence we should get HPs without madvise */
> + res = test_mmap_thp(NONE, pmdsize);
> + ASSERT_EQ(res, 1);
> +
> + res = test_mmap_thp(HUGE, pmdsize);
> + ASSERT_EQ(res, 1);
> +
> + res = test_mmap_thp(COLLAPSE, pmdsize);
> + ASSERT_EQ(res, 1);
Seems res is not being used other than saving the return value for assertions.
Why don't you do the assertion at once, e.g., ASSERT_EQ(test_mmap_thp(...), 1)?
No strong opinion, but I think that could make code shorter and easier to read.
> +}
> +
> +TEST_F(prctl_thp_disable_except_madvise, nofork)
> +{
> + int res = 0;
> +
> + res = prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED, NULL, NULL);
> + ASSERT_EQ(res, 0);
Again, I think 'res' can be removed.
> + prctl_thp_disable_except_madvise(_metadata, self->pmdsize);
> +}
> +
> +TEST_F(prctl_thp_disable_except_madvise, fork)
> +{
> + int res = 0, ret = 0;
> + pid_t pid;
> +
> + res = prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED, NULL, NULL);
> + ASSERT_EQ(res, 0);
Ditto.
> +
> + /* Make sure prctl changes are carried across fork */
> + pid = fork();
> + ASSERT_GE(pid, 0);
> +
> + if (!pid)
> + prctl_thp_disable_except_madvise(_metadata, self->pmdsize);
> +
> + wait(&ret);
> + if (WIFEXITED(ret))
> + ret = WEXITSTATUS(ret);
> + else
> + ret = -EINVAL;
> + ASSERT_EQ(ret, 0);
> +}
> +
> FIXTURE(prctl_thp_disable_completely)
> {
> struct thp_settings settings;
> --
> 2.47.3
Thanks,
SJ
