[PATCH v7 10/10] selftests/mm/cow: Add tests for anonymous small-sized THP

[Ryan Roberts <ryan.roberts@xxxxxxx>]

Add tests similar to the existing PMD-sized THP tests, but which operate
on memory backed by (PTE-mapped) small-sized THP. This reuses all the
existing infrastructure. If the test suite detects that small-sized THP
is not supported by the kernel, the new tests are skipped.

Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
 tools/testing/selftests/mm/cow.c | 71 +++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index d03c453cfd5c..3efc395c7077 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -29,15 +29,49 @@
 #include "../../../../mm/gup_test.h"
 #include "../kselftest.h"
 #include "vm_util.h"
+#include "thp_settings.h"
 
 static size_t pagesize;
 static int pagemap_fd;
 static size_t pmdsize;
+static int nr_thpsmallsizes;
+static size_t thpsmallsizes[20];
 static int nr_hugetlbsizes;
 static size_t hugetlbsizes[10];
 static int gup_fd;
 static bool has_huge_zeropage;
 
+static int sz2ord(size_t size)
+{
+	return __builtin_ctzll(size / pagesize);
+}
+
+static int detect_smallthp_sizes(size_t sizes[], int max)
+{
+	int count = 0;
+	unsigned long orders;
+	size_t kb;
+	int i;
+
+	/* thp not supported at all. */
+	if (!pmdsize)
+		return 0;
+
+	orders = thp_supported_orders();
+
+	/* Only interested in small-sized THP (less than PMD-size). */
+	for (i = 0; i < sz2ord(pmdsize); i++) {
+		if (!(orders & (1UL << i)))
+			continue;
+		kb = (pagesize >> 10) << i;
+		sizes[count++] = kb * 1024;
+		ksft_print_msg("[INFO] detected small-sized THP size: %zu KiB\n",
+			       kb);
+	}
+
+	return count;
+}
+
 static void detect_huge_zeropage(void)
 {
 	int fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page",
@@ -1113,6 +1147,23 @@ static void run_anon_test_case(struct test_case const *test_case)
 		run_with_partial_mremap_thp(test_case->fn, test_case->desc, pmdsize);
 		run_with_partial_shared_thp(test_case->fn, test_case->desc, pmdsize);
 	}
+	for (i = 0; i < nr_thpsmallsizes; i++) {
+		size_t size = thpsmallsizes[i];
+		struct thp_settings settings = *thp_current_settings();
+
+		settings.hugepages[sz2ord(pmdsize)].enabled = THP_NEVER;
+		settings.hugepages[sz2ord(size)].enabled = THP_ALWAYS;
+		thp_push_settings(&settings);
+
+		run_with_pte_mapped_thp(test_case->fn, test_case->desc, size);
+		run_with_pte_mapped_thp_swap(test_case->fn, test_case->desc, size);
+		run_with_single_pte_of_thp(test_case->fn, test_case->desc, size);
+		run_with_single_pte_of_thp_swap(test_case->fn, test_case->desc, size);
+		run_with_partial_mremap_thp(test_case->fn, test_case->desc, size);
+		run_with_partial_shared_thp(test_case->fn, test_case->desc, size);
+
+		thp_pop_settings();
+	}
 	for (i = 0; i < nr_hugetlbsizes; i++)
 		run_with_hugetlb(test_case->fn, test_case->desc,
 				 hugetlbsizes[i]);
@@ -1134,6 +1185,7 @@ static int tests_per_anon_test_case(void)
 
 	if (pmdsize)
 		tests += 8;
+	tests += 6 * nr_thpsmallsizes;
 	return tests;
 }
 
@@ -1691,12 +1743,24 @@ static int tests_per_non_anon_test_case(void)
 int main(int argc, char **argv)
 {
 	int err;
+	struct thp_settings default_settings;
 
 	pagesize = getpagesize();
 	pmdsize = read_pmd_pagesize();
-	if (pmdsize)
+	if (pmdsize) {
+		/* Only if THP is supported. */
+		thp_read_settings(&default_settings);
+		default_settings.hugepages[sz2ord(pmdsize)].enabled = THP_GLOBAL;
+		thp_save_settings();
+		thp_push_settings(&default_settings);
+
 		ksft_print_msg("[INFO] detected PMD-mapped THP size: %zu KiB\n",
 			       pmdsize / 1024);
+
+		nr_thpsmallsizes = detect_smallthp_sizes(thpsmallsizes,
+						    ARRAY_SIZE(thpsmallsizes));
+	}
+
 	nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,
 						    ARRAY_SIZE(hugetlbsizes));
 	detect_huge_zeropage();
@@ -1715,6 +1779,11 @@ int main(int argc, char **argv)
 	run_anon_thp_test_cases();
 	run_non_anon_test_cases();
 
+	if (pmdsize) {
+		/* Only if THP is supported. */
+		thp_restore_settings();
+	}
+
 	err = ksft_get_fail_cnt();
 	if (err)
 		ksft_exit_fail_msg("%d out of %d tests failed\n",
-- 
2.25.1