[RFC PATCH 5/8] mm/damon/core-test: add a unit test for the feedback loop algorithm

[SeongJae Park <sj@kernel.org>]

Implement a simple kunit test for testing the behavior of the core logic
of the goal-oriented feedback-driven DAMOS quota auto-tuning.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core-test.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
index f405d79dc623..c2b8cb25a195 100644
--- a/mm/damon/core-test.h
+++ b/mm/damon/core-test.h
@@ -447,6 +447,37 @@ static void damos_test_filter_out(struct kunit *test)
 	damos_free_filter(f);
 }
 
+static void damon_test_feed_loop_next_input(struct kunit *test)
+{
+	unsigned long last_input = 900000, current_score = 200;
+
+	/*
+	 * If current score is lower than the goal, which is always 10,000
+	 * (read the comment on damon_feed_loop_next_input()'s comment), next
+	 * input should be higher than the last input.
+	 */
+	KUNIT_EXPECT_GT(test,
+			damon_feed_loop_next_input(last_input, current_score),
+			last_input);
+
+	/*
+	 * If current score is higher than the goal, next input should be lower
+	 * than the last input.
+	 */
+	current_score = 250000000;
+	KUNIT_EXPECT_LT(test,
+			damon_feed_loop_next_input(last_input, current_score),
+			last_input);
+
+	/*
+	 * The next input depends on the distance between the current score and
+	 * the goal
+	 */
+	KUNIT_EXPECT_GT(test,
+			damon_feed_loop_next_input(last_input, 200),
+			damon_feed_loop_next_input(last_input, 2000));
+}
+
 static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_target),
 	KUNIT_CASE(damon_test_regions),
@@ -463,6 +494,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_moving_sum),
 	KUNIT_CASE(damos_test_new_filter),
 	KUNIT_CASE(damos_test_filter_out),
+	KUNIT_CASE(damon_test_feed_loop_next_input),
 	{},
 };
 
-- 
2.34.1