[6/8] selftests/damon: implement test for min/max_nr_regions

diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index 356b4e9a515d..1e2e98cc809d 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/tools/testing/selftests/damon/Makefile
@@ -13,7 +13,7 @@  TEST_PROGS = debugfs_attrs.sh debugfs_schemes.sh debugfs_target_ids.sh
 TEST_PROGS += sysfs.sh
 TEST_PROGS += sysfs_update_schemes_tried_regions_wss_estimation.py
 TEST_PROGS += damos_quota.py damos_quota_goal.py damos_apply_interval.py
-TEST_PROGS += damos_tried_regions.py
+TEST_PROGS += damos_tried_regions.py damon_nr_regions.py
 TEST_PROGS += reclaim.sh lru_sort.sh
 
 # regression tests (reproducers of previously found bugs)
diff --git a/tools/testing/selftests/damon/damon_nr_regions.py b/tools/testing/selftests/damon/damon_nr_regions.py
new file mode 100644
index 000000000000..dd2735923c59
--- /dev/null
+++ b/tools/testing/selftests/damon/damon_nr_regions.py
@@ -0,0 +1,85 @@ 
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import subprocess
+import time
+
+import _damon_sysfs
+
+def test_nr_regions(real_nr_regions, min_nr_regions, max_nr_regions):
+    '''
+    Create process of the given 'real_nr_regions' regions, monitor it using
+    DAMON with given '{min,max}_nr_regions' monitoring parameter.
+
+    Exit with non-zero return code if the given {min,max}_nr_regions is not
+    kept.
+    '''
+    sz_region = 10 * 1024 * 1024
+    proc = subprocess.Popen(['./access_memory_even', '%d' % real_nr_regions,
+                             '%d' % sz_region])
+
+    # stat every monitored regions
+    kdamonds = _damon_sysfs.Kdamonds([_damon_sysfs.Kdamond(
+            contexts=[_damon_sysfs.DamonCtx(
+                monitoring_attrs=_damon_sysfs.DamonAttrs(
+                    min_nr_regions=min_nr_regions,
+                    max_nr_regions=max_nr_regions),
+                ops='vaddr',
+                targets=[_damon_sysfs.DamonTarget(pid=proc.pid)],
+                schemes=[_damon_sysfs.Damos(action='stat',
+                    )] # schemes
+                )] # contexts
+            )]) # kdamonds
+
+    err = kdamonds.start()
+    if err is not None:
+        proc.terminate()
+        print('kdamond start failed: %s' % err)
+        exit(1)
+
+    collected_nr_regions = []
+    while proc.poll() is None:
+        time.sleep(0.1)
+        err = kdamonds.kdamonds[0].update_schemes_tried_regions()
+        if err is not None:
+            proc.terminate()
+            print('tried regions update failed: %s' % err)
+            exit(1)
+
+        scheme = kdamonds.kdamonds[0].contexts[0].schemes[0]
+        if scheme.tried_regions is None:
+            proc.terminate()
+            print('tried regions is not collected')
+            exit(1)
+
+        nr_tried_regions = len(scheme.tried_regions)
+        if nr_tried_regions <= 0:
+            proc.terminate()
+            print('tried regions is not created')
+            exit(1)
+        collected_nr_regions.append(nr_tried_regions)
+        if len(collected_nr_regions) > 10:
+            break
+    proc.terminate()
+    kdamonds.stop()
+
+    test_name = 'nr_regions test with %d/%d/%d real/min/max nr_regions' % (
+            real_nr_regions, min_nr_regions, max_nr_regions)
+    if (collected_nr_regions[0] < min_nr_regions or
+        collected_nr_regions[-1] > max_nr_regions):
+        print('fail %s' % test_name)
+        print('number of regions that collected are:')
+        for nr in collected_nr_regions:
+            print(nr)
+        exit(1)
+    print('pass %s ' % test_name)
+
+def main():
+    # test min_nr_regions larger than real nr regions
+    test_nr_regions(10, 20, 100)
+
+    # test max_nr_regions smaller than real nr regions
+    test_nr_regions(15, 3, 10)
+
+if __name__ == '__main__':
+    main()