[PATCH v2 2/2] mm/damon/tests/core-kunit: test PSI goal values with explicit samples

[Karl Mehltretter <kmehltretter@gmail.com>]

Test the PSI current-value helper with explicit totals so the result does
not depend on the test system's memory pressure. Cover an unmeasured
consist goal, unmeasured temporal goals with zero and nonzero effective
quotas, and measured rounds for both tuners. Check last_psi_total after
each call.

With the old unmeasured-round behavior retained in the helper, the
temporal check with a nonzero effective quota fails.

Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 mm/damon/tests/core-kunit.h | 43 +++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 5ff0436c58441..a30040826874e 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -910,6 +910,48 @@ static void damos_test_commit_quota_goal(struct kunit *test)
 			});
 }
 
+static void damos_test_set_psi_current_val(struct kunit *test)
+{
+	struct damos s = {
+		.quota.goal_tuner = DAMOS_QUOTA_GOAL_TUNER_CONSIST,
+	};
+	struct damos_quota_goal goal = {
+		.metric = DAMOS_QUOTA_SOME_MEM_PSI_US,
+		.target_value = 100,
+		.last_psi_total = U64_MAX,
+	};
+
+	/* uninitialized last_psi_total keeps the consist tuner quota */
+	damos_set_psi_current_val(1000, &goal, &s);
+	KUNIT_EXPECT_EQ(test, goal.current_value, 100ul);
+	KUNIT_EXPECT_EQ(test, goal.last_psi_total, 1000ull);
+
+	/* initialized last_psi_total gives the delta */
+	damos_set_psi_current_val(1030, &goal, &s);
+	KUNIT_EXPECT_EQ(test, goal.current_value, 30ul);
+	KUNIT_EXPECT_EQ(test, goal.last_psi_total, 1030ull);
+
+	/* temporal tuner keeps a zero quota */
+	s.quota.goal_tuner = DAMOS_QUOTA_GOAL_TUNER_TEMPORAL;
+	s.quota.esz = 0;
+	goal.last_psi_total = U64_MAX;
+	damos_set_psi_current_val(2000, &goal, &s);
+	KUNIT_EXPECT_EQ(test, goal.current_value, 100ul);
+	KUNIT_EXPECT_EQ(test, goal.last_psi_total, 2000ull);
+
+	/* temporal tuner keeps a non-zero quota */
+	s.quota.esz = SZ_64K;
+	goal.last_psi_total = U64_MAX;
+	damos_set_psi_current_val(3000, &goal, &s);
+	KUNIT_EXPECT_EQ(test, goal.current_value, 0ul);
+	KUNIT_EXPECT_EQ(test, goal.last_psi_total, 3000ull);
+
+	/* temporal tuner uses the measured PSI delta */
+	damos_set_psi_current_val(3250, &goal, &s);
+	KUNIT_EXPECT_EQ(test, goal.current_value, 250ul);
+	KUNIT_EXPECT_EQ(test, goal.last_psi_total, 3250ull);
+}
+
 static void damos_test_commit_quota_goals_for(struct kunit *test,
 		struct damos_quota_goal *dst_goals, int nr_dst_goals,
 		struct damos_quota_goal *src_goals, int nr_src_goals)
@@ -1947,6 +1989,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_nr_accesses_mvsum),
 	KUNIT_CASE(damos_test_new_filter),
 	KUNIT_CASE(damos_test_commit_quota_goal),
+	KUNIT_CASE(damos_test_set_psi_current_val),
 	KUNIT_CASE(damos_test_commit_quota_goals),
 	KUNIT_CASE(damos_test_commit_quota),
 	KUNIT_CASE(damos_test_commit_dests),
-- 
2.53.0