From: "Kiryl Shutsemau (Meta)" <[email protected]> The harness's MADV_DONTNEED thread zaps 1 to 32 pages at a time, never a whole PMD-aligned area, and only a zap that covers a full table frees the table itself (CONFIG_PT_RECLAIM).
Make the thread zap a whole PMD-aligned area about one iteration in 64, and keep the fine-grained zaps as the common case. The new case frees page tables, racing that against a collapse walking the same table. Assisted-by: LLM Tested-by: Muhammad Usama Anjum <[email protected]> Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/khugepaged_race.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/mm/khugepaged_race.c b/tools/testing/selftests/mm/khugepaged_race.c index 1f4aa23834db..c3478b5123e2 100644 --- a/tools/testing/selftests/mm/khugepaged_race.c +++ b/tools/testing/selftests/mm/khugepaged_race.c @@ -118,8 +118,21 @@ static void *dontneed_fn(void *arg) unsigned long page_idx = rand_page(&seed); unsigned long nr = 1UL << (rand_r(&seed) % 6); /* 1..32 pages */ - madvise(region + page_idx * page_size, - room_from(page_idx, nr) * page_size, MADV_DONTNEED); + /* + * Now and then zap a whole PMD-aligned area: only a zap that + * covers the full table frees the table itself (CONFIG_PT_RECLAIM). + */ + if (!(rand_r(&seed) % 64)) { + unsigned long area = page_idx / + (hpage_pmd_size / page_size); + + madvise(region + area * hpage_pmd_size, + hpage_pmd_size, MADV_DONTNEED); + } else { + madvise(region + page_idx * page_size, + room_from(page_idx, nr) * page_size, + MADV_DONTNEED); + } usleep(rand_r(&seed) % 500); } return NULL; -- 2.54.0
