selftests/damon: add a test for DAMOS quota goal

Add a selftest for DAMOS quota goal.  It tests the feature by setting a
user_input metric based goal, change the current feedback, and check if
the effective quota size is increased and decreased as expected.

Link: https://lkml.kernel.org/r/20240502172718.74166-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/Makefile

@@ -16,7 +16,7 @@ TEST_PROGS += debugfs_target_ids_pid_leak.sh
 TEST_PROGS += sysfs.sh sysfs_update_removed_scheme_dir.sh
 TEST_PROGS += sysfs_update_schemes_tried_regions_hang.py
 TEST_PROGS += sysfs_update_schemes_tried_regions_wss_estimation.py
-TEST_PROGS += damos_quota.py damos_apply_interval.py
+TEST_PROGS += damos_quota.py damos_quota_goal.py damos_apply_interval.py
 TEST_PROGS += reclaim.sh lru_sort.sh
 
 include ../lib.mk

tools/testing/selftests/damon/damos_quota_goal.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import subprocess
+import time
+
+import _damon_sysfs
+
+def main():
+    # access two 10 MiB memory regions, 2 second per each
+    sz_region = 10 * 1024 * 1024
+    proc = subprocess.Popen(['./access_memory', '2', '%d' % sz_region, '2000'])
+
+    goal = _damon_sysfs.DamosQuotaGoal(
+            metric=_damon_sysfs.qgoal_metric_user_input, target_value=10000)
+    kdamonds = _damon_sysfs.Kdamonds([_damon_sysfs.Kdamond(
+            contexts=[_damon_sysfs.DamonCtx(
+                ops='vaddr',
+                targets=[_damon_sysfs.DamonTarget(pid=proc.pid)],
+                schemes=[_damon_sysfs.Damos(
+                    action='stat',
+                    quota=_damon_sysfs.DamosQuota(
+                        goals=[goal], reset_interval_ms=100),
+                    )] # schemes
+                )] # contexts
+            )]) # kdamonds
+
+    err = kdamonds.start()
+    if err != None:
+        print('kdamond start failed: %s' % err)
+        exit(1)
+
+    score_values_to_test = [0, 15000, 5000, 18000]
+    while proc.poll() == None:
+        if len(score_values_to_test) == 0:
+            time.sleep(0.1)
+            continue
+
+        goal.current_value = score_values_to_test.pop(0)
+        expect_increase = goal.current_value < goal.target_value
+
+        err = kdamonds.kdamonds[0].commit_schemes_quota_goals()
+        if err is not None:
+            print('commit_schemes_quota_goals failed: %s' % err)
+            exit(1)
+
+        err = kdamonds.kdamonds[0].update_schemes_effective_quotas()
+        if err is not None:
+            print('before-update_schemes_effective_quotas failed: %s' % err)
+            exit(1)
+        last_effective_bytes = goal.effective_bytes
+
+        time.sleep(0.5)
+
+        err = kdamonds.kdamonds[0].update_schemes_effective_quotas()
+        if err is not None:
+            print('after-update_schemes_effective_quotas failed: %s' % err)
+            exit(1)
+
+        print('score: %s, effective quota: %d -> %d (%.3fx)' % (
+            goal.current_value, last_effective_bytes, goal.effective_bytes,
+            goal.effective_bytes / last_effective_bytes
+            if last_effective_bytes != 0 else -1.0))
+
+        if last_effective_bytes == goal.effective_bytes:
+            print('efective bytes not changed: %d' % goal.effective_bytes)
+            exit(1)
+
+        increased = last_effective_bytes < goal.effective_bytes
+        if expect_increase != increased:
+            print('expectation of increase (%s) != increased (%s)' %
+                  (expect_increase, increased))
+            exit(1)
+        last_effective_bytes = goal.effective_bytes
+
+if __name__ == '__main__':
+    main()