selftests/damon: implement DAMOS tried regions test

Implement a test for DAMOS tried regions command of DAMON sysfs interface.
It ensures the expected number of monitoring regions are created using an
artificial memory access pattern generator program.

Link: https://lkml.kernel.org/r/20240625180538.73134-5-sj@kernel.orgSigned-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

@@ -13,6 +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 += reclaim.sh lru_sort.sh
 
 # regression tests (reproducers of previously found bugs)

tools/testing/selftests/damon/damos_tried_regions.py

+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import subprocess
+import time
+
+import _damon_sysfs
+
+def main():
+    # repeatedly access even-numbered ones in 14 regions of 10 MiB size
+    sz_region = 10 * 1024 * 1024
+    proc = subprocess.Popen(['./access_memory_even', '14', '%d' % sz_region])
+
+    # stat every monitored regions
+    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',
+                    )] # 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()
+
+    collected_nr_regions.sort()
+    sample = collected_nr_regions[4]
+    print('50-th percentile nr_regions: %d' % sample)
+    print('expectation (>= 14) is %s' % 'met' if sample >= 14 else 'not met')
+    if collected_nr_regions[4] < 14:
+        print('full nr_regions:')
+        print('\n'.join(collected_nr_regions))
+        exit(1)
+
+if __name__ == '__main__':
+    main()