From: "Kiryl Shutsemau (Meta)" <[email protected]> The mthp_khugepaged context runs the generic cases at a sub-PMD order, which answers how many folios of that order a range ends up with. It cannot say which window they are in, so "the populated window collapsed and its neighbour did not" and "one window collapsed twice" look alike.
Add four cases that check each aligned window on its own, with the folio-order helpers in vm_util: - collapse_order_single_window: only the populated window collapses; - collapse_order_partial_window: the default max_ptes_none lets a window with one present PTE collapse; - collapse_order_max_ptes_none: with max_ptes_none=0 a full window collapses and one missing a page does not; - collapse_order_mixed_sources: sources that are already large folios of a smaller order collapse to the target. Each case faults its region before MADV_HUGEPAGE with only the target order enabled, so the sources are order 0 and the result can only come from khugepaged. They wait for a full pass rather than for the result to appear: without a completed pass, "not collapsed" and "not scanned yet" are the same thing. Assisted-by: Claude-Code:claude-opus-5 Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/khugepaged.c | 219 ++++++++++++++++++++++++ 1 file changed, 219 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 69e0fc4b12fb..bcaef17e430d 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -31,6 +31,8 @@ static unsigned long page_size; static int hpage_pmd_nr; static int anon_order; static int collapse_order; +static int pagemap_fd = -1; +static int kpageflags_fd = -1; #define PID_SMAPS "/proc/self/smaps" #define TEST_FILE "collapse_test_file" @@ -1268,6 +1270,205 @@ static void madvise_retracted_page_tables(struct collapse_context *c, ksft_test_result_report(exit_status, "%s\n", __func__); } +/* Smallest order khugepaged will consider for mTHP collapse. */ +#define MIN_MTHP_ORDER 2 + +/* + * Order-parameterized collapse cases for the mthp_khugepaged context. What + * they add over the generic cases run under that context is per-window + * detection: which aligned window collapsed, and which of its neighbours did + * not. check_huge() answers how many folios of the order the range holds, + * which cannot tell one window from another. + * + * The region is faulted before MADV_HUGEPAGE, and the target order is only + * enabled for madvise, so the sources are always order 0 and the collapse + * product can only have come from khugepaged. + */ +static size_t mthp_window_size(void) +{ + return page_size << collapse_order; +} + +static void mthp_push_target_order(void) +{ + struct thp_settings settings = *thp_current_settings(); + int i; + + /* + * The target order, for madvise only, and nothing else enabled: the + * cases fault their region before MADV_HUGEPAGE, so the sources are + * order 0 whatever -s asked the fault path for. That matters for the + * cases built around a hole -- a large source folio would fill it in + * and the window would collapse after all. + * collapse_order_mixed_sources enables the source order it wants on + * top of this. + */ + settings.thp_enabled = THP_NEVER; + for (i = 0; i < NR_ORDERS; i++) + settings.hugepages[i].enabled = THP_NEVER; + settings.hugepages[collapse_order].enabled = THP_MADVISE; + thp_push_settings(&settings); +} + +static bool window_collapsed(void *p, size_t len) +{ + return is_range_backed_by_folio_orders(p, len, collapse_order, + pagemap_fd, kpageflags_fd); +} + +/* No aligned window in [p, p + len) is backed at the target order. */ +static bool window_not_collapsed(void *p, size_t len) +{ + size_t window = mthp_window_size(); + char *addr = p; + + for (; len >= window; addr += window, len -= window) { + if (window_collapsed(addr, window)) + return false; + } + return true; +} + +static bool khugepaged_wait_full_pass(void) +{ + /* Wait up to 30 seconds for the pass to complete. */ + return khugepaged_full_pass(30); +} + +static void collapse_order_single_window(struct collapse_context *c, + struct mem_ops *ops) +{ + size_t window = mthp_window_size(); + void *p; + + mthp_push_target_order(); + + p = ops->setup_area(1); + ops->fault(p, window, 2 * window); + if (!window_not_collapsed(p, hpage_pmd_size)) + ksft_exit_fail_msg("Unexpected large folio after fault\n"); + + madvise(p, hpage_pmd_size, MADV_HUGEPAGE); + ksft_print_msg("Collapse one fully populated window..."); + if (!khugepaged_wait_full_pass()) + fail("Timeout"); + else if (window_collapsed(p + window, window) && + window_not_collapsed(p, window) && + window_not_collapsed(p + 2 * window, + hpage_pmd_size - 2 * window)) + success("OK"); + else + fail("Fail"); + + validate_memory(p, window, 2 * window); + ops->cleanup_area(p, hpage_pmd_size); + thp_pop_settings(); + ksft_test_result_report(exit_status, "%s\n", __func__); +} + +static void collapse_order_partial_window(struct collapse_context *c, + struct mem_ops *ops) +{ + void *p; + + mthp_push_target_order(); + + p = ops->setup_area(1); + ops->fault(p, 0, page_size); + if (!window_not_collapsed(p, hpage_pmd_size)) + ksft_exit_fail_msg("Unexpected large folio after fault\n"); + + madvise(p, hpage_pmd_size, MADV_HUGEPAGE); + ksft_print_msg("Collapse window with single PTE entry present..."); + if (!khugepaged_wait_full_pass()) + fail("Timeout"); + else if (window_collapsed(p, mthp_window_size())) + success("OK"); + else + fail("Fail"); + + validate_memory(p, 0, page_size); + ops->cleanup_area(p, hpage_pmd_size); + thp_pop_settings(); + ksft_test_result_report(exit_status, "%s\n", __func__); +} + +static void collapse_order_max_ptes_none(struct collapse_context *c, + struct mem_ops *ops) +{ + struct thp_settings settings; + size_t window = mthp_window_size(); + void *p; + + mthp_push_target_order(); + settings = *thp_current_settings(); + settings.khugepaged.max_ptes_none = 0; + thp_push_settings(&settings); + + p = ops->setup_area(1); + ops->fault(p, 0, 2 * window - page_size); + if (!window_not_collapsed(p, hpage_pmd_size)) + ksft_exit_fail_msg("Unexpected large folio after fault\n"); + + madvise(p, hpage_pmd_size, MADV_HUGEPAGE); + ksft_print_msg("Collapse full window, not the one missing a page..."); + if (!khugepaged_wait_full_pass()) + fail("Timeout"); + else if (window_collapsed(p, window) && + window_not_collapsed(p + window, window)) + success("OK"); + else + fail("Fail"); + + validate_memory(p, 0, 2 * window - page_size); + ops->cleanup_area(p, hpage_pmd_size); + thp_pop_settings(); + thp_pop_settings(); + ksft_test_result_report(exit_status, "%s\n", __func__); +} + +static void collapse_order_mixed_sources(struct collapse_context *c, + struct mem_ops *ops) +{ + struct thp_settings settings; + void *p; + + if (collapse_order <= MIN_MTHP_ORDER) { + ksft_test_result_skip("%s: no source order below target\n", + __func__); + return; + } + + mthp_push_target_order(); + + /* Fault the whole region as order-MIN_MTHP_ORDER folios. */ + settings = *thp_current_settings(); + settings.hugepages[MIN_MTHP_ORDER].enabled = THP_ALWAYS; + thp_push_settings(&settings); + p = ops->setup_area(1); + ops->fault(p, 0, hpage_pmd_size); + thp_pop_settings(); + + if (!is_range_backed_by_folio_orders(p, hpage_pmd_size, MIN_MTHP_ORDER, + pagemap_fd, kpageflags_fd)) + ksft_exit_fail_msg("Region not backed by order-%d folios after fault\n", + MIN_MTHP_ORDER); + + madvise(p, hpage_pmd_size, MADV_HUGEPAGE); + ksft_print_msg("Collapse region backed by smaller large folios..."); + if (!khugepaged_wait_full_pass()) + fail("Timeout"); + else if (window_collapsed(p, hpage_pmd_size)) + success("OK"); + else + fail("Fail"); + + validate_memory(p, 0, hpage_pmd_size); + ops->cleanup_area(p, hpage_pmd_size); + thp_pop_settings(); + ksft_test_result_report(exit_status, "%s\n", __func__); +} + static void usage(void) { fprintf(stderr, "\nUsage: ./khugepaged [OPTIONS] <test type> [dir]\n\n"); @@ -1436,6 +1637,20 @@ int main(int argc, char **argv) parse_test_type(argc, argv); + if (mthp_khugepaged_context && + !(thp_supported_orders() & (1UL << collapse_order))) + ksft_exit_skip("Order %d is not a supported anon THP order\n", + collapse_order); + + if (mthp_khugepaged_context) { + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); + if (pagemap_fd < 0) + ksft_exit_fail_perror("open(/proc/self/pagemap)"); + kpageflags_fd = open("/proc/kpageflags", O_RDONLY); + if (kpageflags_fd < 0) + ksft_exit_fail_perror("open(/proc/kpageflags)"); + } + setbuf(stdout, NULL); /* @@ -1498,6 +1713,10 @@ int main(int argc, char **argv) TEST(collapse_empty, madvise_context, anon_ops); TEST(collapse_single_mthp, mthp_khugepaged_context, anon_ops); + TEST(collapse_order_single_window, mthp_khugepaged_context, anon_ops); + TEST(collapse_order_partial_window, mthp_khugepaged_context, anon_ops); + TEST(collapse_order_max_ptes_none, mthp_khugepaged_context, anon_ops); + TEST(collapse_order_mixed_sources, mthp_khugepaged_context, anon_ops); TEST(collapse_single_pte_entry, khugepaged_context, anon_ops); TEST(collapse_single_pte_entry, khugepaged_context, read_only_file_ops); -- 2.54.0
