From: "Kiryl Shutsemau (Meta)" <[email protected]> mTHP collapse went in for 7.2 with no functional selftest coverage. Every khugepaged collapse case is PMD-shaped, down to the detection: it reads smaps AnonHugePages, which cannot see anything below the PMD order.
I am also reworking khugepaged's collapse mechanism, and that wants a suite worth trusting before the mechanism changes underneath it. Nothing here depends on the rework: everything passes on an unmodified kernel and documents what khugepaged already does. This version sits on top of Baolin's anon mTHP collapse selftests [1], now in mm-new. His mthp_khugepaged context and per-order detection are what the new cases need, so they go in there rather than bringing their own. Four existing cases fail on the environment rather than on the kernel: - The collapse wait is a fixed three seconds, whatever a huge page costs to build. Scale it with the PMD size. - collapse_compound_extreme wants a 512M folio from the fault path. Skip it where the PMD is that large. - The page cache caps folio order below the PMD order where a PMD is 512M, so nothing can hold a PMD-sized page cache folio. Skip the shmem and file cases there. - The swap cases ask a best-effort MADV_PAGEOUT for an exact swap count. Ask again before calling it a failure. This is why the suite now runs on arm64 with 64K pages. Then the new coverage: - Folio-order helpers in vm_util, and folio_order_check to validate them against the kernel before any collapse test trusts them. - Four order-parameterized anon collapse cases, plus mixed sources by source order, at every supported order by default. - A shared-source write race: a co-sharer writing throughout a collapse and the collapsing side must not see each other's pages. - khugepaged_full_pass(), which steps the daemon one scan at a time through the sysfs wake path, and khugepaged_sync_check to hold it to exactly one attributed collapse per step. - khugepaged_race, racing faults, MADV_DONTNEED, pins, fork and mremap against collapse, checked by content and by KASAN and lockdep. Tested on mm-new (8086604be973), with KASAN, lockdep, DEBUG_VM and page_table_check, in 16G guests: x86-64 4K 190 pass, 1 skip, 0 fail arm64 64K 228 pass, 5 skip, 0 fail The skips are structural: mixed sources declines at the smallest order, and at 64K collapse_compound_extreme and the shmem components skip as above. Changes since v1: - Rebased onto [1] (Baolin Wang), which this overlapped and which is in mm-new now, so this applies on top of it. This series' own -o mode is gone in favour of his context. - A plain ./khugepaged and ./khugepaged_race now run everything they can: every supported order, and every mode, occupancy and pressure axis. The options only narrow that down (Mike Rapoport). - The fixes to existing cases come first, then the infrastructure and the new tests, each next to what it validates (Mike Rapoport). - The completion barrier helper comes before the tests that use it, so no case carries a throwaway implementation of it (Mike Rapoport). - Changelogs and comments rewritten to be read rather than parsed (Mike Rapoport). - One new patch: retry the swapout, which is what made collapse_max_ptes_swap flaky at 64K. - Dropped the swap-skip patch, an equivalent has landed (Alexander Gordeev). - Review fixes: masked failures, system state left behind on bail-out paths, arguments taken on trust (Sashiko). [1] https://lore.kernel.org/all/[email protected] Kiryl Shutsemau (Meta) (17): selftests/mm: skip collapse_compound_extreme where the PMD is too large selftests/mm: scale khugepaged's collapse wait with the PMD size selftests/mm: skip khugepaged page cache cases without a PMD folio selftests/mm: retry the swapout the khugepaged swap cases rely on selftests/mm: move is_backed_by_folio() into vm_util selftests/mm: add folio-order check for address ranges selftests/mm: add folio-order detection self-check selftests/mm: add khugepaged completion barrier helper selftests/mm: add order-parameterized khugepaged collapse cases selftests/mm: parameterize the mixed-source collapse case by source order selftests/mm: cover a shared-source collapse write race selftests/mm: run every supported collapse order by default selftests/mm: verify synchronous khugepaged driving is attributable selftests/mm: add khugepaged race harness selftests/mm: race collapse of windows with holes selftests/mm: add memory-pressure threads to the khugepaged race harness selftests/mm: zap whole PTE tables in the khugepaged race harness tools/testing/selftests/mm/Makefile | 3 + .../testing/selftests/mm/folio_order_check.c | 137 +++++ tools/testing/selftests/mm/hmm-tests.c | 1 - .../testing/selftests/mm/hugepage_settings.c | 72 ++- .../testing/selftests/mm/hugepage_settings.h | 3 + tools/testing/selftests/mm/khugepaged.c | 466 +++++++++++++- tools/testing/selftests/mm/khugepaged_race.c | 571 ++++++++++++++++++ .../selftests/mm/khugepaged_sync_check.c | 217 +++++++ tools/testing/selftests/mm/run_vmtests.sh | 8 +- .../selftests/mm/split_huge_page_test.c | 62 -- tools/testing/selftests/mm/vm_util.c | 145 +++++ tools/testing/selftests/mm/vm_util.h | 10 + 12 files changed, 1599 insertions(+), 96 deletions(-) create mode 100644 tools/testing/selftests/mm/folio_order_check.c create mode 100644 tools/testing/selftests/mm/khugepaged_race.c create mode 100644 tools/testing/selftests/mm/khugepaged_sync_check.c base-commit: 8086604be9733378461a5534c39cb72635226b23 -- 2.54.0
