> On 9/23/26 12:54, Yeoreum Yun wrote: > >> > >> > >> On 9/21/26 6:35 PM, Yeoreum Yun wrote: > >>> There are intermittent failures in collapse_max_ptes_swap() and > >>> collapse_max_ptes_shared() when using the khugepaged_context: > >>> > >>> // while running ./khugepaged -s 2 > >>> > >>> # Run test: collapse_max_ptes_shared (khugepaged:anon) > >>> # Allocate huge page... OK > >>> # Share huge page over fork()... OK > >>> # Trigger CoW on page 1023 of 2048... OK > >>> # Maybe collapse with max_ptes_shared exceeded.... OK > >>> # Trigger CoW on page 1024 of 2048... Fail > >>> Bail out! Unexpected huge page > >>> # Planned tests != run tests (26 != 23) > >>> # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 > >>> > >>> # Run test: collapse_max_ptes_swap (khugepaged:anon) > >>> # Swapout 257 of 2048 pages... OK > >>> # Maybe collapse with max_ptes_swap exceeded.... OK > >>> # Swapout 256 of 2048 pages... OK > >>> Bail out! Unexpected huge page > >>> # Planned tests != run tests (26 != 17) > >>> # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:0 error:0 > >>> > >>> This happens because khugepaged may collapse the pages before > >>> wait_for_scan() > >>> is called, causing a sanity check that expects uncollapsed pages to fail. > >>> > >>> For example, in collapse_max_ptes_swap(), after faulting the pages back in > >>> and paging out up to max_ptes_swap pages, khugepaged may collapse them > >>> again > >>> before c->collapse() is called. > >>> > >>> To prevent this, mark the VMA with MADV_NOHUGEPAGE after it has been > >>> collapsed by wait_for_scan() for anon. This prevents khugepaged from > >>> collapsing it again before c->collapse() is called. > >>> > >>> This failure was observed on NVIDIA Spark with 16KB page. > >>> > >>> Signed-off-by: Yeoreum Yun <[email protected]> > >>> --- > >>> tools/testing/selftests/mm/khugepaged.c | 3 +++ > >>> 1 file changed, 3 insertions(+) > >>> > >>> diff --git a/tools/testing/selftests/mm/khugepaged.c > >>> b/tools/testing/selftests/mm/khugepaged.c > >>> index c32244b565658..1aad4bb427ece 100644 > >>> --- a/tools/testing/selftests/mm/khugepaged.c > >>> +++ b/tools/testing/selftests/mm/khugepaged.c > >>> @@ -578,6 +578,9 @@ static bool wait_for_scan(const char *msg, char *p, > >>> size_t len, > >>> usleep(TICK); > >>> } > >>> + if (!strncmp(ops->name, "anon", 4)) > >> > >> We usually use the 'if (ops == &__anon_ops)' check in this file to identify > >> anonymous test cases. > >> > >> With that, LGTM. > >> Reviewed-by: Baolin Wang <[email protected]> > >> Tested-by: Baolin Wang <[email protected]> > > > > I think this is merged at mm/mm-unstable already So, I'll send > > another patch to change it with is_anon(). > > Unless it is in mm-stable we can reasonably squash stuff or resend. This > shouldn't be an independent patch.
I see. Thanks! -- Sincerely, Yeoreum Yun
