[PATCH 03/11] mm/damon/tests/core-kunit: test damon_rand()

[SJ Park <sj@kernel.org>]

Commit 9012c4e647df ("mm/damon: replace damon_rand() with a per-ctx
lockless PRNG") optimized DAMON for better performance.  Add a kunit
test for ensuring the bounds of the output.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/tests/core-kunit.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index aef7e0553cba4..0124f83b39b83 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -1547,6 +1547,20 @@ static void damon_test_walk_control_obsolete(struct kunit *test)
 	damon_destroy_ctx(ctx);
 }
 
+static void damon_test_rand(struct kunit *test)
+{
+	struct damon_ctx ctx;
+	int i;
+
+	prandom_seed_state(&ctx.rnd_state, get_random_u64());
+	for (i = 0; i < 10000; i++) {
+		unsigned long rnd = damon_rand(&ctx, 0, 10);
+
+		KUNIT_EXPECT_GE(test, rnd, 0);
+		KUNIT_EXPECT_LE(test, rnd, 9);
+	}
+}
+
 static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_target),
 	KUNIT_CASE(damon_test_regions),
@@ -1578,6 +1592,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_apply_min_nr_regions),
 	KUNIT_CASE(damon_test_is_last_region),
 	KUNIT_CASE(damon_test_walk_control_obsolete),
+	KUNIT_CASE(damon_test_rand),
 	{},
 };
 
-- 
2.47.3