On 07/08/2026 12:36 pm, Kiryl Shutsemau wrote: > 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. I've tested them on arm64 vm and more tests are passing instead of getting skipped. Hence:
Tested-by: Muhammad Usama Anjum <[email protected]> > > 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 -- Thanks, Usama
