* [PATCH v2 1/2] selftests/damon/_damon_sysfs: support kdamond refresh_ms
2026-06-29 14:49 [PATCH v2 0/2] selftests/damon: test kdamond refresh_ms SJ Park
@ 2026-06-29 14:49 ` SJ Park
2026-06-29 14:49 ` [PATCH v2 2/2] selftests/damon/sysfs_refresh: test " SJ Park
1 sibling, 0 replies; 3+ messages in thread
From: SJ Park @ 2026-06-29 14:49 UTC (permalink / raw)
To: Andrew Morton
Cc: Ruslan Valiyev, SJ Park, Shuah Khan, damon, linux-kernel,
linux-kselftest, linux-mm
From: Ruslan Valiyev <linuxoid@gmail.com>
The Kdamond class has no way to set the kdamond-level 'refresh_ms' sysfs
file, which makes DAMON periodically update the read-only sysfs files
(DAMOS stats, tuned monitoring intervals and the kdamond pid) on its own.
Add a 'refresh_ms' parameter to Kdamond. When it is set (including to
zero, to disable the periodic update), write it before turning the
kdamond on, so tests can exercise the auto-update behavior. Leaving it
unset keeps the previous behavior of not touching the file, so callers
running against kernels without the feature are unaffected.
Link: https://lore.kernel.org/20260602131217.2210912-2-linuxoid@gmail.com
Signed-off-by: Ruslan Valiyev <linuxoid@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
tools/testing/selftests/damon/_damon_sysfs.py | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index c197ab99bcc0a..e6a2265d721e8 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -698,12 +698,14 @@ class DamonCtx:
class Kdamond:
state = None
pid = None
+ refresh_ms = None
contexts = None
idx = None # index of this kdamond between siblings
kdamonds = None # parent
- def __init__(self, contexts=[]):
+ def __init__(self, contexts=[], refresh_ms=None):
self.contexts = contexts
+ self.refresh_ms = refresh_ms
for idx, context in enumerate(self.contexts):
context.idx = idx
context.kdamond = self
@@ -726,6 +728,11 @@ class Kdamond:
err = context.stage()
if err is not None:
return err
+ if self.refresh_ms is not None:
+ err = write_file(os.path.join(self.sysfs_dir(), 'refresh_ms'),
+ '%d' % self.refresh_ms)
+ if err is not None:
+ return err
err = write_file(os.path.join(self.sysfs_dir(), 'state'), 'on')
if err is not None:
return err
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v2 2/2] selftests/damon/sysfs_refresh: test kdamond refresh_ms
2026-06-29 14:49 [PATCH v2 0/2] selftests/damon: test kdamond refresh_ms SJ Park
2026-06-29 14:49 ` [PATCH v2 1/2] selftests/damon/_damon_sysfs: support " SJ Park
@ 2026-06-29 14:49 ` SJ Park
1 sibling, 0 replies; 3+ messages in thread
From: SJ Park @ 2026-06-29 14:49 UTC (permalink / raw)
To: Andrew Morton
Cc: Ruslan Valiyev, SJ Park, Shuah Khan, damon, linux-kernel,
linux-kselftest, linux-mm
From: Ruslan Valiyev <linuxoid@gmail.com>
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
Signed-off-by: Ruslan Valiyev <linuxoid@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
tools/testing/selftests/damon/Makefile | 1 +
.../testing/selftests/damon/sysfs_refresh.py | 75 +++++++++++++++++++
2 files changed, 76 insertions(+)
create mode 100755 tools/testing/selftests/damon/sysfs_refresh.py
diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index 2180c328a8252..ece244e5c5b95 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/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 b/tools/testing/selftests/damon/sysfs_refresh.py
new file mode 100755
index 0000000000000..012b7e8f509f5
--- /dev/null
+++ b/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()
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread