split_huge_page_test can fail for the following reasons:
1. During the test, khugepaged may collapse previously split pages again,
causing intermittent failures.
2. Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on
AArch64”),
glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations
made by memalign(). The underlying VMA may start at a different address
from the aligned address returned by memalign(). Moreover, a subsequent
madvise(MADV_HUGEPAGE) call does not split the VMA because it already
has the same advice.
This causes the test to fail because the check_huge_xxx() helpers
incorrectly require the address returned by memalign() to match the
VMA start address reported in /proc/self/smaps.
Address these issues by applying MADV_NOHUGEPAGE after faulting in the
huge page, preventing khugepaged from collapsing it again, and by replacing
the use of /proc/self/smaps in the check_huge_xxx() helpers with
/proc/self/pagemap and /proc/kpageflags.
This patch based on mm-unstable
---
Changes in v2:
- rebase to mm-unstable.
- add message in case of failure of madvise() with MADV_NOHUGEPAGE.
- fix wrong setup expected_huge in check_huge_shmem().
- Link to v1:
https://lore.kernel.org/r/[email protected]
---
Yeoreum Yun (2):
kselftest: mm: prevent random failure of huge page split for khugepaged
kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx()
helper
tools/testing/selftests/mm/split_huge_page_test.c | 15 +++
tools/testing/selftests/mm/vm_util.c | 130 +++++++++++++---------
tools/testing/selftests/mm/vm_util.h | 1 +
3 files changed, 92 insertions(+), 54 deletions(-)
---
base-commit: 169393fff5d1ec2690934067eeb95544ff5ebdd7
change-id: 20260820-fix_split-f44939ec44b8
Best regards,
--
Sincerely,
Yeoreum Yun
