+ selftests-damon-sysfs_refresh-test-kdamond-refresh_ms.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests/damon/sysfs_refresh: test kdamond refresh_ms
has been added to the -mm mm-new branch.  Its filename is
     selftests-damon-sysfs_refresh-test-kdamond-refresh_ms.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-damon-sysfs_refresh-test-kdamond-refresh_ms.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Ruslan Valiyev <linuxoid@gmail.com>
Subject: selftests/damon/sysfs_refresh: test kdamond refresh_ms
Date: Mon, 29 Jun 2026 07:49:26 -0700

Writing a non-zero value to a kdamond's 'refresh_ms' sysfs file should
make DAMON periodically update the read-only sysfs files on its own,
without the user writing update keywords such as 'update_schemes_stats' to
the 'state' file.  This behavior has no test coverage.

Add a test that starts a kdamond with refresh_ms set and a 'stat' scheme
whose default access pattern matches every monitored region, then polls
the scheme's 'nr_tried' stats file directly, without requesting an update.
The value can become non-zero only via the periodic refresh, so the test
confirms refresh_ms works; with refresh_ms disabled the stat stays zero
and the test fails.

Link: https://lore.kernel.org/20260602131217.2210912-3-linuxoid@gmail.com
Link: https://lore.kernel.org/20260629144927.134237-3-sj@kernel.org
Signed-off-by: Ruslan Valiyev <linuxoid@gmail.com>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/damon/Makefile         |    1 
 tools/testing/selftests/damon/sysfs_refresh.py |   75 +++++++++++++++
 2 files changed, 76 insertions(+)

--- a/tools/testing/selftests/damon/Makefile~selftests-damon-sysfs_refresh-test-kdamond-refresh_ms
+++ a/tools/testing/selftests/damon/Makefile
@@ -13,6 +13,7 @@ TEST_PROGS += sysfs.py
 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 damon_nr_regions.py
+TEST_PROGS += sysfs_refresh.py
 TEST_PROGS += reclaim.sh lru_sort.sh
 
 # regression tests (reproducers of previously found bugs)
diff --git a/tools/testing/selftests/damon/sysfs_refresh.py a/tools/testing/selftests/damon/sysfs_refresh.py
new file mode 100755
--- /dev/null
+++ a/tools/testing/selftests/damon/sysfs_refresh.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import subprocess
+import time
+
+import _damon_sysfs
+
+def main():
+    # Continuously access a memory region for far longer than the test needs,
+    # so the kdamond always has a live target to monitor while we poll.
+    sz_region = 10 * 1024 * 1024
+    proc = subprocess.Popen(
+            ['./access_memory', '1', '%d' % sz_region, '60000', 'repeat'])
+
+    # A 'stat' scheme with the default (maximally wide) access pattern matches
+    # every monitored region, so its 'nr_tried' stat increases as the kdamond
+    # runs.  refresh_ms should make DAMON update the schemes' stats files under
+    # sysfs on its own, without a manual 'update_schemes_stats' request.
+    kdamond = _damon_sysfs.Kdamond(
+            refresh_ms=100,
+            contexts=[_damon_sysfs.DamonCtx(
+                ops='vaddr',
+                targets=[_damon_sysfs.DamonTarget(pid=proc.pid)],
+                schemes=[_damon_sysfs.Damos(action='stat')],
+                )])
+    kdamonds = _damon_sysfs.Kdamonds([kdamond])
+
+    err = kdamonds.start()
+    if err is not None:
+        # Kernels older than the refresh_ms feature have no such file; treat
+        # that as unsupported rather than a failure.
+        if not os.path.exists(os.path.join(kdamond.sysfs_dir(), 'refresh_ms')):
+            proc.terminate()
+            proc.wait()
+            print('kdamond has no refresh_ms file; skipping')
+            exit(_damon_sysfs.ksft_skip)
+        proc.terminate()
+        proc.wait()
+        print('kdamond start failed: %s' % err)
+        exit(1)
+
+    scheme = kdamond.contexts[0].schemes[0]
+    nr_tried_path = os.path.join(scheme.sysfs_dir(), 'stats', 'nr_tried')
+
+    try:
+        # Poll the stat file directly.  We never request an update (e.g.
+        # 'update_schemes_stats'), so 'nr_tried' can become non-zero only
+        # through the periodic refresh that refresh_ms enables.
+        nr_tried = 0
+        deadline = time.monotonic() + 10
+        while time.monotonic() < deadline:
+            if proc.poll() is not None:
+                print('the access_memory target exited unexpectedly')
+                exit(1)
+            content, err = _damon_sysfs.read_file(nr_tried_path)
+            if err is not None:
+                print('reading %s failed: %s' % (nr_tried_path, err))
+                exit(1)
+            nr_tried = int(content)
+            if nr_tried > 0:
+                break
+            time.sleep(0.1)
+    finally:
+        kdamonds.stop()
+        proc.terminate()
+        proc.wait()
+
+    if nr_tried == 0:
+        print('refresh_ms did not auto-update the schemes stats')
+        exit(1)
+
+if __name__ == '__main__':
+    main()
_

Patches currently in -mm which might be from linuxoid@gmail.com are

selftests-damon-_damon_sysfs-support-kdamond-refresh_ms.patch
selftests-damon-sysfs_refresh-test-kdamond-refresh_ms.patch