From: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Kiryl Shutsemau <kirill@shutemov.name>,
akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
rppt@kernel.org
Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, usama.anjum@arm.com,
usama.arif@linux.dev, nico.pache@linux.dev, ziy@nvidia.com,
baohua@kernel.org, dev.jain@arm.com, hughd@google.com,
lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com,
ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com,
vbabka@kernel.org, agordeev@linux.ibm.com, jgg@ziepe.ca,
leon@kernel.org, kernel-team@meta.com,
"Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: Re: [PATCH v5 11/19] selftests/mm: add order-parameterized khugepaged collapse cases
Date: Thu, 10 Sep 2026 12:59:14 +0800 [thread overview]
Message-ID: <162af233-ae81-40e6-8c71-d13a41b5d892@linux.alibaba.com> (raw)
In-Reply-To: <20260908125105.1510704-12-kirill@shutemov.name>
On 9/8/26 8:50 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
>
> 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 order-sized window they landed in, so "the populated
> window collapsed" and "the empty window next to it collapsed instead" look
> alike.
>
> Add four cases that check each 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: LLM
> Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
> ---
> tools/testing/selftests/mm/khugepaged.c | 212 ++++++++++++++++++++++++
> 1 file changed, 212 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index e9bc8fe8a1f8..fb4efaf67c40 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"
> @@ -1207,6 +1209,198 @@ 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
> +
> +/* Time budget for one khugepaged pass in the collapse_order_* cases */
> +#define MTHP_PASS_TIMEOUT_S 30
> +
> +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;
> +
> + /*
> + * Only the target order, and only for madvise: the cases fault their
> + * region first, so the sources stay order 0 whatever -s asked for.
> + */
> + 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 all_windows_at_order(void *p, size_t len)
> +{
> + return is_range_backed_by_order(p, len, collapse_order,
> + pagemap_fd, kpageflags_fd);
Like I mentioned in patch 8, you can implement these helpers using
check_large_folios() in vm_util.c. Then you do not need to add new
'pagemap_fd' and 'kpageflags_fd' variables.
> +}
> +
> +static bool any_window_at_order(void *p, size_t len)
> +{
> + size_t window = mthp_window_size();
> + char *addr = p;
> +
> + for (; len >= window; addr += window, len -= window) {
> + if (all_windows_at_order(addr, window))
> + return true;
> + }
> + return false;
> +}
> +
> +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 (any_window_at_order(p, hpage_pmd_size))
> + ksft_exit_fail_msg("Unexpected large folio after fault\n");
> +
> + if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))
> + ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
> + ksft_print_msg("Collapse one fully populated window...");
> + if (!khugepaged_full_pass(MTHP_PASS_TIMEOUT_S))
> + fail("Timeout");
> + else if (all_windows_at_order(p + window, window) &&
> + !any_window_at_order(p, window) &&
> + !any_window_at_order(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 (any_window_at_order(p, hpage_pmd_size))
> + ksft_exit_fail_msg("Unexpected large folio after fault\n");
> +
> + if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))
> + ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
> + ksft_print_msg("Collapse window with single PTE entry present...");
> + if (!khugepaged_full_pass(MTHP_PASS_TIMEOUT_S))
> + fail("Timeout");
> + else if (all_windows_at_order(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 (any_window_at_order(p, hpage_pmd_size))
> + ksft_exit_fail_msg("Unexpected large folio after fault\n");
> +
> + if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))
> + ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
> + ksft_print_msg("Collapse full window, not the one missing a page...");
> + if (!khugepaged_full_pass(MTHP_PASS_TIMEOUT_S))
> + fail("Timeout");
> + else if (all_windows_at_order(p, window) &&
> + !any_window_at_order(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();
> +
> + 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();
> +
> + /*
> + * The allocator can fall back to smaller folios under fragmentation;
> + * having nothing to collapse from is not a failure.
> + */
> + if (!is_range_backed_by_order(p, hpage_pmd_size, MIN_MTHP_ORDER,
> + pagemap_fd, kpageflags_fd)) {
> + ksft_print_msg("No order-%d sources to collapse...",
> + MIN_MTHP_ORDER);
> + skip("Skip");
> + ops->cleanup_area(p, hpage_pmd_size);
> + thp_pop_settings();
> + ksft_test_result_report(exit_status, "%s\n", __func__);
> + return;
> + }
> +
> + if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))
> + ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
> + ksft_print_msg("Collapse region backed by smaller large folios...");
> + if (!khugepaged_full_pass(MTHP_PASS_TIMEOUT_S))
> + fail("Timeout");
> + else if (all_windows_at_order(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");
> @@ -1375,6 +1569,20 @@ 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);
This check can be moved into parse_test_type(), where the
'mthp_khugepaged' parameter is parsed.
> +
> + 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)");
When you change to use check_large_folios(), these fds can be removed
from this file.
> + }
> +
> setbuf(stdout, NULL);
>
> /*
> @@ -1425,6 +1633,10 @@ 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);
These test cases look good to me. Thanks.
next prev parent reply other threads:[~2026-09-10 4:59 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-08 12:50 [PATCH v5 00/19] selftests/mm: improve khugepaged coverage Kiryl Shutsemau
2026-09-08 12:50 ` [PATCH v5 01/19] selftests/mm: raise the khugepaged test-case cap Kiryl Shutsemau
2026-09-09 7:42 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 02/19] selftests/mm: skip collapse_compound_extreme() where the PMD is too large Kiryl Shutsemau
2026-09-09 7:51 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 03/19] selftests/mm: scale khugepaged's collapse wait with the PMD size Kiryl Shutsemau
2026-09-09 7:59 ` Baolin Wang
2026-09-09 10:09 ` Kiryl Shutsemau
2026-09-09 10:17 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 04/19] selftests/mm: skip khugepaged page cache cases without a PMD folio Kiryl Shutsemau
2026-09-09 8:21 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 05/19] selftests/mm: make the swap cases' swapout reliable Kiryl Shutsemau
2026-09-09 8:59 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 06/19] selftests/mm: stop khugepaged during the MADV_COLLAPSE cases Kiryl Shutsemau
2026-09-09 9:55 ` Baolin Wang
2026-09-09 10:41 ` Kiryl Shutsemau
2026-09-10 6:27 ` Baolin Wang
2026-09-10 10:59 ` Kiryl Shutsemau
2026-09-10 11:06 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 07/19] selftests/mm: move is_backed_by_folio() into vm_util Kiryl Shutsemau
2026-09-09 9:16 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 08/19] selftests/mm: add folio-order check for address ranges Kiryl Shutsemau
2026-09-09 10:01 ` Baolin Wang
2026-09-10 10:45 ` Kiryl Shutsemau
2026-09-10 11:14 ` Baolin Wang
2026-09-10 13:04 ` Kiryl Shutsemau
2026-09-11 2:50 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 09/19] selftests/mm: add folio-order detection self-check Kiryl Shutsemau
2026-09-08 12:50 ` [PATCH v5 10/19] selftests/mm: add khugepaged completion barrier helper Kiryl Shutsemau
2026-09-10 1:17 ` Baolin Wang
2026-09-08 12:50 ` [PATCH v5 11/19] selftests/mm: add order-parameterized khugepaged collapse cases Kiryl Shutsemau
2026-09-10 4:59 ` Baolin Wang [this message]
2026-09-10 10:53 ` Kiryl Shutsemau
2026-09-08 12:50 ` [PATCH v5 12/19] selftests/mm: parameterize the mixed-source collapse case by source order Kiryl Shutsemau
2026-09-10 5:09 ` Baolin Wang
2026-09-10 10:58 ` Kiryl Shutsemau
2026-09-08 12:50 ` [PATCH v5 13/19] selftests/mm: cover a shared-source collapse write race Kiryl Shutsemau
2026-09-08 21:02 ` Kiryl Shutsemau
2026-09-08 12:51 ` [PATCH v5 14/19] selftests/mm: run every supported collapse order by default Kiryl Shutsemau
2026-09-10 6:07 ` Baolin Wang
2026-09-08 12:51 ` [PATCH v5 15/19] selftests/mm: check that one khugepaged pass collapses one window Kiryl Shutsemau
2026-09-08 12:51 ` [PATCH v5 16/19] selftests/mm: add khugepaged race harness Kiryl Shutsemau
2026-09-08 21:34 ` Kiryl Shutsemau
2026-09-08 12:51 ` [PATCH v5 17/19] selftests/mm: race the collapse of windows with holes Kiryl Shutsemau
2026-09-08 12:51 ` [PATCH v5 18/19] selftests/mm: add memory-pressure threads to the khugepaged race harness Kiryl Shutsemau
2026-09-08 12:51 ` [PATCH v5 19/19] selftests/mm: zap whole PTE tables in " Kiryl Shutsemau
2026-09-08 19:41 ` [PATCH v5 00/19] selftests/mm: improve khugepaged coverage Andrew Morton
2026-09-08 21:36 ` Kiryl Shutsemau
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