[RFC PATCH v1.3 03/11] mm/damon/tests/core-kunit: test damon_rand()

[SeongJae Park]

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: SeongJae Park <sj@xxxxxxxxxx>
---
 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 1cfb8c176b873..282670b0fa908 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -1460,6 +1460,20 @@ static void damon_test_is_last_region(struct kunit *test)
 	damon_free_target(t);
 }
 
+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),
@@ -1489,6 +1503,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_set_filters_default_reject),
 	KUNIT_CASE(damon_test_apply_min_nr_regions),
 	KUNIT_CASE(damon_test_is_last_region),
+	KUNIT_CASE(damon_test_rand),
 	{},
 };
 
-- 
2.47.3