[RFC PATCH 00/13] mm/damon: optimize out nr_accesses_bp

[SeongJae Park]

TLDR: Replace damon_region->nr_accesses_bp, which is easy to be wrong,
with a simpler on-demand moving sum function, damon_nr_accesses_mvsum().

Background
==========

DAMON's monitoring output (access pattern snapshot, or more technically
speaking, damon_region->nr_accesses) is completed once per aggregation
interval, which is 100 ms by default. Users can arbitrarily increase
the interval for demand. Under the suggested intervals auto-tuning
setup, it can span up to 200 seconds. If the aggregation interval is
too long, the snapshot users cannot use it in reasonable time. To
mitigate this, we introduced a new field of damon_region, namely
nr_accesses_bp. It contains a pseudo moving sum of nr_accesses in bp
units and is updated for each sampling interval.

It turned out keeping it correctly updated every sampling interval is
not that easy. From online parameter update feature development and
more experimental hacks, we found it is easy to be corrupted. Once it
is corrupted, DAMON's monitoring outputs become quite insane. Hence we
added a few validation checks. It is easy to be corrupted because it
requires every update per sampling interval to be correct.

Solution
========

There is no real reason to keep it updated every sampling interval. Due
to the simple pseudo-moving sum mechanism and existing helper field
(last_nr_accesses), we can also calculate the pseudo moving sum on
demand in a much simpler way.

Implement a function for getting the pseudo moving sum on demand, and
replace nr_accessses_bp uses with the new function. Also remove no more
needed tests for nr_accesses_bp and the per-sampling interval update
functions. Finally, remove the nr_accesses_bp. The new function is
quite simple.

Discussion
==========

Depending on the use case, multiple nr_accesses readers could be
executed in the same kdamond_fn() main loop iteration, which is executed
once per sampling interval. Such readers include DAMON region exporting
tracepoints (damon_[region_]aggregated and damos_before_apply), DAMOS,
and DAMON sysfs interface logic for update_schemes_tried_regions
command. In this case, the new function will be called multiple times
and this could be overhead compared to the old logic, which simply reads
the field without any additional work. Nonetheless, the new function is
quite simple. And the new approach does nothing while there is no need
to read. The old approach had to execute its update function for each
region for every sampling interval. Hence the new approach is believed
to be even more lightweight in common case, and the overhead is anyway
negligible.

One more advantage of this change is that one field from the
damon_region struct is removed. On setups that uses a high number of
DAMON regions, this could be a potential memory space benefit.

Patches Sequence
================

Patch 1 introduces the new function for getting the pseudo moving sum of
nr_accesses on demands. Patch 2 implements a unit test for the new
function's internal logic. Patches 3-5 replace uses of nr_accesses_bp
in DAMOS, tracepoints and DAMON sysfs interface with the new function,
respectively. Patches 6-8 removes nr_accesses_bp validation functions
in DAMON core, one by one. Patches 9 and 10 further remove tests and
test helper for nr_accesses_bp, respectively. Patches 11 removes the
setups and updates or nr_accesses_bp field. Patch 12 removes the
function that was used for updating nr_accesses_bp field with its unit
test, which is the single remaining caller of the function. Finally,
patch 13 removes damon_region->nr_accesses_bp field.

SeongJae Park (13):
mm/damon: introduce damon_nr_accesses_mvsum()
mm/damon/tests/core-kunit: test damon_mvsum()
mm/damon/core: use damon_nr_accesses_mvsum() in __damos_valid_target()
mm/damon/core: use damon_nr_accesses_mvsum() for damos region tracing
mm/damon/sysfs-schemes: use damon_nr_accesses_mvsum() for damo regions
mm/damon/core: remove damon_warn_fix_nr_accesses_corruption()
mm/damon/core: remove damon_verify_reset_aggregated()
mm/damon/core: remove damon_verify_merge_regions_of()
mm/damon/tests/core-kunit: remove nr_accesses_bp setup and tests
selftests/damon/drgn_dump_damon_status: do not dump nr_accesses_bp
mm/damon/core: remove nr_accesses_bp setups and updates
mm/damon/core: remove damon_moving_sum() and its unit test
mm/damon: remove damon_region->nr_accesses_bp

include/linux/damon.h | 12 +-
include/trace/events/damon.h | 8 +-
mm/damon/core.c | 171 +++++++-----------
mm/damon/sysfs-schemes.c | 6 +-
mm/damon/tests/core-kunit.h | 37 ++--
.../selftests/damon/drgn_dump_damon_status.py | 1 -
6 files changed, 91 insertions(+), 144 deletions(-)


base-commit: 6c6dd09066e98c4afcf61f404d5b2b87f35e3321
--
2.47.3

[SeongJae Park]

Add a simple unit test for damon_nr_accesses_mvsum()'s internal core
logic, damon_mvsum(). The test contains cases for just-started windows,
partially completed windows, and just-completed windows.

Signed-off-by: SeongJae Park <s...@kernel.org>
---
mm/damon/tests/core-kunit.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 4e448c08c724a..cdab14396250f 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -623,6 +623,30 @@ static void damon_test_moving_sum(struct kunit *test)
}
}

+static void damon_test_mvsum(struct kunit *test)
+{
+ unsigned long input_expects[] = {
+ /* current value, last value, remaining window (bp) */
+ 0, 49, 10000, 49, /* 0 + 49 * 1 */
+ 3, 10, 7000, 10, /* 3 + 10 * 0.7 */
+ 3, 10, 5000, 8, /* 3 + 10 * 0.5 */
+ 32, 100, 1000, 42, /* 32 + 100 * 0.1 */
+ 42, 49, 0, 42, /* 42 + 49 * 0 */
+ };
+
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(input_expects); i += 4) {
+ unsigned long current_nr = input_expects[i];
+ unsigned long last_nr = input_expects[i + 1];
+ unsigned long left_window_bp = input_expects[i + 2];
+ unsigned long expect = input_expects[i + 3];
+
+ KUNIT_EXPECT_EQ(test, damon_mvsum(current_nr, last_nr,
+ left_window_bp), expect);
+ }
+}
+
static void damos_test_new_filter(struct kunit *test)
{
struct damos_filter *filter;
@@ -1501,6 +1525,7 @@ static struct kunit_case damon_test_cases[] = {
KUNIT_CASE(damon_test_update_monitoring_result),
KUNIT_CASE(damon_test_set_attrs),
KUNIT_CASE(damon_test_moving_sum),
+ KUNIT_CASE(damon_test_mvsum),
KUNIT_CASE(damos_test_new_filter),
KUNIT_CASE(damos_test_commit_quota_goal),
KUNIT_CASE(damos_test_commit_quota_goals),
--
2.47.3

[SeongJae Park]

DAMON core unit tests set up nr_accesses_bp for representing realistic
damon_region, and also test the field. nr_acceses_bp is no longer being
used for a real use case. Remove the setup and tests.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 8 --------
1 file changed, 8 deletions(-)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index cdab14396250f..d1f019ab6fc25 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -118,7 +118,6 @@ static void damon_test_aggregate(struct kunit *test)
kunit_skip(test, "region alloc fail");
}
r->nr_accesses = accesses[it][ir];
- r->nr_accesses_bp = accesses[it][ir] * 10000;
damon_add_region(r, t);
}
it++;
@@ -155,7 +154,6 @@ static void damon_test_split_at(struct kunit *test)
damon_free_target(t);
kunit_skip(test, "region alloc fail");
}
- r->nr_accesses_bp = 420000;
r->nr_accesses = 42;
r->last_nr_accesses = 15;
r->age = 10;
@@ -168,7 +166,6 @@ static void damon_test_split_at(struct kunit *test)
KUNIT_EXPECT_EQ(test, r_new->ar.start, 25ul);
KUNIT_EXPECT_EQ(test, r_new->ar.end, 100ul);

- KUNIT_EXPECT_EQ(test, r->nr_accesses_bp, r_new->nr_accesses_bp);
KUNIT_EXPECT_EQ(test, r->nr_accesses, r_new->nr_accesses);
KUNIT_EXPECT_EQ(test, r->last_nr_accesses, r_new->last_nr_accesses);
KUNIT_EXPECT_EQ(test, r->age, r_new->age);
@@ -191,7 +188,6 @@ static void damon_test_merge_two(struct kunit *test)
kunit_skip(test, "region alloc fail");
}
r->nr_accesses = 10;
- r->nr_accesses_bp = 100000;
r->age = 9;
damon_add_region(r, t);
r2 = damon_new_region(100, 300);
@@ -200,7 +196,6 @@ static void damon_test_merge_two(struct kunit *test)
kunit_skip(test, "second region alloc fail");
}
r2->nr_accesses = 20;
- r2->nr_accesses_bp = 200000;
r2->age = 21;
damon_add_region(r2, t);

@@ -208,7 +203,6 @@ static void damon_test_merge_two(struct kunit *test)
KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
KUNIT_EXPECT_EQ(test, r->ar.end, 300ul);
KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u);
- KUNIT_EXPECT_EQ(test, r->nr_accesses_bp, 160000u);
KUNIT_EXPECT_EQ(test, r->age, 17u);

i = 0;
@@ -256,7 +250,6 @@ static void damon_test_merge_regions_of(struct kunit *test)
kunit_skip(test, "region alloc fail");
}
r->nr_accesses = nrs[i];
- r->nr_accesses_bp = nrs[i] * 10000;
damon_add_region(r, t);
}

@@ -556,7 +549,6 @@ static void damon_test_update_monitoring_result(struct kunit *test)
kunit_skip(test, "region alloc fail");

r->nr_accesses = 15;
- r->nr_accesses_bp = 150000;
r->age = 20;

new_attrs = (struct damon_attrs){
--
2.47.3

[SeongJae Park]

Changes from RFC v1
- RFC v1: https://lore.kernel.org/202606191934...@kernel.org
- Avoid divide-by-zero from zero aggregation interval.
- Call damon_nr_accesses_mvsum() for damos tracing only when it is enabled.
- Remove obsolete mentioning of nr_accesses_bp in comments.

SeongJae Park (13):
mm/damon: introduce damon_nr_accesses_mvsum()
mm/damon/tests/core-kunit: test damon_mvsum()
mm/damon/core: use damon_nr_accesses_mvsum() in __damos_valid_target()
mm/damon/core: use damon_nr_accesses_mvsum() for damos region tracing
mm/damon/sysfs-schemes: use damon_nr_accesses_mvsum() for damo regions
mm/damon/core: remove damon_warn_fix_nr_accesses_corruption()
mm/damon/core: remove damon_verify_reset_aggregated()
mm/damon/core: remove damon_verify_merge_regions_of()
mm/damon/tests/core-kunit: remove nr_accesses_bp setup and tests
selftests/damon/drgn_dump_damon_status: do not dump nr_accesses_bp
mm/damon/core: remove nr_accesses_bp setups and updates
mm/damon/core: remove damon_moving_sum() and its unit test
mm/damon: remove damon_region->nr_accesses_bp

include/linux/damon.h | 12 +-
include/trace/events/damon.h | 8 +-

mm/damon/core.c | 180 +++++++-----------

mm/damon/sysfs-schemes.c | 6 +-
mm/damon/tests/core-kunit.h | 37 ++--
.../selftests/damon/drgn_dump_damon_status.py | 1 -

6 files changed, 96 insertions(+), 148 deletions(-)


base-commit: a74bff7aaa4b3a64070425b4b367a459388a8233
--
2.47.3

[SeongJae Park]

Add a simple unit test for damon_nr_accesses_mvsum()'s internal core
logic, damon_mvsum(). The test contains cases for just-started windows,
partially completed windows, and just-completed windows.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 4e448c08c724a..cdab14396250f 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SeongJae Park]

DAMON core unit tests set up nr_accesses_bp for representing realistic
damon_region, and also test the field. nr_acceses_bp is no longer being
used for a real use case. Remove the setup and tests.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 8 --------
1 file changed, 8 deletions(-)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index cdab14396250f..d1f019ab6fc25 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SeongJae Park]

function's internal logic. Patch 3 updates monitoring logic to ready
for safe use of the new function. Patches 4-6 replace uses of

nr_accesses_bp in DAMOS, tracepoints and DAMON sysfs interface with the

new function, respectively. Patches 7-9 removes nr_accesses_bp
validation functions in DAMON core, one by one. Patches 10 and 11

further remove tests and test helper for nr_accesses_bp, respectively.

Patches 12 removes the setups and updates or nr_accesses_bp field.
Patches 13-15 cleans up function parameters that are no more being used
due to the previous patch. Patch 16 removes the function that was used

for updating nr_accesses_bp field with its unit test, which is the

single remaining caller of the function. Finally, patch 17 removes
damon_region->nr_accesses_bp field.

Changes from RFC v1.1
- RFC v1.1: https://lore.kernel.org/202606201722...@kernel.org
- Handle next_aggregation_sis < passed_sample_intervals in
nr_accesses_mvsum().
- Always rescale ->last_nr_accesss for intervals change.
- Remove unused attrs params from damon_update_region_access_rate() and
its callers.

Changes from RFC v1
- RFC v1: https://lore.kernel.org/202606191934...@kernel.org
- Avoid divide-by-zero from zero aggregation interval.
- Call damon_nr_accesses_mvsum() for damos tracing only when it is enabled.

- Remove obsolete mentions of nr_accesses_bp in comments.

SeongJae Park (17):

mm/damon: introduce damon_nr_accesses_mvsum()
mm/damon/tests/core-kunit: test damon_mvsum()

mm/damon/core: always update ->last_nr_accesses for intervals change

mm/damon/core: use damon_nr_accesses_mvsum() in __damos_valid_target()
mm/damon/core: use damon_nr_accesses_mvsum() for damos region tracing
mm/damon/sysfs-schemes: use damon_nr_accesses_mvsum() for damo regions
mm/damon/core: remove damon_warn_fix_nr_accesses_corruption()
mm/damon/core: remove damon_verify_reset_aggregated()
mm/damon/core: remove damon_verify_merge_regions_of()
mm/damon/tests/core-kunit: remove nr_accesses_bp setup and tests
selftests/damon/drgn_dump_damon_status: do not dump nr_accesses_bp
mm/damon/core: remove nr_accesses_bp setups and updates

mm/damon/core: remove attrs param from
damon_update_region_access_rate()
mm/damonn/paddr: remove attrs param from __damon_pa_check_access()
mm/damon/vaddr: remove attrs param from __damon_va_check_access()

mm/damon/core: remove damon_moving_sum() and its unit test
mm/damon: remove damon_region->nr_accesses_bp

include/linux/damon.h | 15 +-
include/trace/events/damon.h | 8 +-
mm/damon/core.c | 198 +++++++-----------
mm/damon/paddr.c | 9 +-

mm/damon/sysfs-schemes.c | 6 +-
mm/damon/tests/core-kunit.h | 37 ++--

mm/damon/vaddr.c | 12 +-
.../selftests/damon/drgn_dump_damon_status.py | 1 -
8 files changed, 116 insertions(+), 170 deletions(-)


base-commit: 6b4f924f70f92679c81959ad6b9234242aab74a7
--
2.47.3

[SeongJae Park]

Add a simple unit test for damon_nr_accesses_mvsum()'s internal core
logic, damon_mvsum(). The test contains cases for just-started windows,
partially completed windows, and just-completed windows.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 4e448c08c724a..cdab14396250f 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SeongJae Park]

DAMON core unit tests set up nr_accesses_bp for representing realistic
damon_region, and also test the field. nr_acceses_bp is no longer being
used for a real use case. Remove the setup and tests.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 8 --------
1 file changed, 8 deletions(-)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index cdab14396250f..d1f019ab6fc25 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SeongJae Park]

function's internal logic. Patch 3 and 4 update monitoring logic and
the new function to ready for safe use on the existing logic. Patches
5-7 replace uses of nr_accesses_bp in DAMOS, tracepoints and DAMON sysfs
interface with the new function, respectively. Patches 8-10 removes

nr_accesses_bp validation functions in DAMON core, one by one. Patches

11 and 12 further remove tests and test helper for nr_accesses_bp,
respectively. Patches 13 removes the setups and updates or
nr_accesses_bp field. Patches 14-16 cleans up function parameters that
are no more being used due to the previous patch. Patch 17 removes the

function that was used for updating nr_accesses_bp field with its unit
test, which is the single remaining caller of the function. Finally,

patch 18 removes damon_region->nr_accesses_bp field.

Changes from RFC v1.2
- RFC v1.2: https://lore.kernel.org/202606211557...@kernel.org
- Explicitly ignore nr_accesses from mvsum at the beginning of
aggregation.
- Fix a typo in a commit message.

Changes from RFC v1.1
- RFC v1.1: https://lore.kernel.org/202606201722...@kernel.org
- Handle next_aggregation_sis < passed_sample_intervals in
nr_accesses_mvsum().

- Always rescale ->last_nr_accesss for parameter changes.

- Remove unused attrs params from damon_update_region_access_rate() and
its callers.
Changes from RFC v1
- RFC v1: https://lore.kernel.org/202606191934...@kernel.org
- Avoid divide-by-zero from zero aggregation interval.
- Call damon_nr_accesses_mvsum() for damos tracing only when it is enabled.
- Remove obsolete mentions of nr_accesses_bp in comments.

SeongJae Park (18):

mm/damon: introduce damon_nr_accesses_mvsum()
mm/damon/tests/core-kunit: test damon_mvsum()
mm/damon/core: always update ->last_nr_accesses for intervals change

mm/damon/core: handle unreset nr_accesses in damon_nr_accesses_mvsum()

mm/damon/core: use damon_nr_accesses_mvsum() in __damos_valid_target()
mm/damon/core: use damon_nr_accesses_mvsum() for damos region tracing
mm/damon/sysfs-schemes: use damon_nr_accesses_mvsum() for damo regions
mm/damon/core: remove damon_warn_fix_nr_accesses_corruption()
mm/damon/core: remove damon_verify_reset_aggregated()
mm/damon/core: remove damon_verify_merge_regions_of()
mm/damon/tests/core-kunit: remove nr_accesses_bp setup and tests
selftests/damon/drgn_dump_damon_status: do not dump nr_accesses_bp
mm/damon/core: remove nr_accesses_bp setups and updates
mm/damon/core: remove attrs param from
damon_update_region_access_rate()
mm/damonn/paddr: remove attrs param from __damon_pa_check_access()
mm/damon/vaddr: remove attrs param from __damon_va_check_access()
mm/damon/core: remove damon_moving_sum() and its unit test
mm/damon: remove damon_region->nr_accesses_bp

include/linux/damon.h | 15 +-
include/trace/events/damon.h | 8 +-

mm/damon/core.c | 201 +++++++-----------

mm/damon/paddr.c | 9 +-
mm/damon/sysfs-schemes.c | 6 +-
mm/damon/tests/core-kunit.h | 37 ++--
mm/damon/vaddr.c | 12 +-
.../selftests/damon/drgn_dump_damon_status.py | 1 -

8 files changed, 119 insertions(+), 170 deletions(-)


base-commit: e08d3bec1dc38cc991fc819afd698bf7bd07bd6d
--
2.47.3

[SeongJae Park]

Add a simple unit test for damon_nr_accesses_mvsum()'s internal core
logic, damon_mvsum(). The test contains cases for just-started windows,
partially completed windows, and just-completed windows.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 4e448c08c724a..cdab14396250f 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SeongJae Park]

DAMON core unit tests set up nr_accesses_bp for representing realistic
damon_region, and also test the field. nr_acceses_bp is no longer being
used for a real use case. Remove the setup and tests.

Signed-off-by: SeongJae Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 8 --------
1 file changed, 8 deletions(-)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index cdab14396250f..d1f019ab6fc25 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h

[SJ Park]

Changes from RFC v1.3
- RFC v1.3: https://lore.kernel.org/202606221421...@kernel.org
- Wordsmith and fixup commit subjects.
- Drop RFC tag.
- Rebase to latest mm-new.

Changes from RFC v1.2
- RFC v1.2: https://lore.kernel.org/202606211557...@kernel.org
- Explicitly ignore nr_accesses from mvsum at the beginning of
aggregation.
- Fix a typo in a commit message.
Changes from RFC v1.1
- RFC v1.1: https://lore.kernel.org/202606201722...@kernel.org
- Handle next_aggregation_sis < passed_sample_intervals in
nr_accesses_mvsum().
- Always rescale ->last_nr_accesss for parameter changes.
- Remove unused attrs params from damon_update_region_access_rate() and
its callers.
Changes from RFC v1
- RFC v1: https://lore.kernel.org/202606191934...@kernel.org
- Avoid divide-by-zero from zero aggregation interval.
- Call damon_nr_accesses_mvsum() for damos tracing only when it is enabled.
- Remove obsolete mentions of nr_accesses_bp in comments.

SJ Park (18):
mm/damon/core: introduce damon_nr_accesses_mvsum()

mm/damon/tests/core-kunit: test damon_mvsum()
mm/damon/core: always update ->last_nr_accesses for intervals change
mm/damon/core: handle unreset nr_accesses in damon_nr_accesses_mvsum()
mm/damon/core: use damon_nr_accesses_mvsum() in __damos_valid_target()
mm/damon/core: use damon_nr_accesses_mvsum() for damos region tracing
mm/damon/sysfs-schemes: use damon_nr_accesses_mvsum() for damo regions
mm/damon/core: remove damon_warn_fix_nr_accesses_corruption()
mm/damon/core: remove damon_verify_reset_aggregated()
mm/damon/core: remove damon_verify_merge_regions_of()
mm/damon/tests/core-kunit: remove nr_accesses_bp setup and tests
selftests/damon/drgn_dump_damon_status: do not dump nr_accesses_bp
mm/damon/core: remove nr_accesses_bp setups and updates
mm/damon/core: remove attrs param from
damon_update_region_access_rate()

mm/damon/paddr: remove attrs param from __damon_pa_check_access()

mm/damon/vaddr: remove attrs param from __damon_va_check_access()
mm/damon/core: remove damon_moving_sum() and its unit test

mm/damon/core: remove damon_region->nr_accesses_bp

include/linux/damon.h | 15 +-
include/trace/events/damon.h | 8 +-
mm/damon/core.c | 201 +++++++-----------
mm/damon/paddr.c | 9 +-
mm/damon/sysfs-schemes.c | 6 +-
mm/damon/tests/core-kunit.h | 37 ++--
mm/damon/vaddr.c | 12 +-
.../selftests/damon/drgn_dump_damon_status.py | 1 -
8 files changed, 119 insertions(+), 170 deletions(-)

base-commit: d74f4c01f930b32580e172a786efbcb352c312f1
--
2.47.3

[SJ Park]

Add a simple unit test for damon_nr_accesses_mvsum()'s internal core
logic, damon_mvsum(). The test contains cases for just-started windows,
partially completed windows, and just-completed windows.

Signed-off-by: SJ Park <s...@kernel.org>

---
mm/damon/tests/core-kunit.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index a00168730445d..ff13d1b1cbc94 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -682,6 +682,30 @@ static void damon_test_moving_sum(struct kunit *test)

@@ -1561,6 +1585,7 @@ static struct kunit_case damon_test_cases[] = {

[SJ Park]

DAMON core unit tests set up nr_accesses_bp for representing realistic
damon_region, and also test the field. nr_acceses_bp is no longer being
used for a real use case. Remove the setup and tests.

Signed-off-by: SJ Park <s...@kernel.org>
---

mm/damon/tests/core-kunit.h | 8 --------
1 file changed, 8 deletions(-)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index ff13d1b1cbc94..e1d22abfbbc22 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -114,7 +114,6 @@ static void damon_test_aggregate(struct kunit *test)

kunit_skip(test, "region alloc fail");
}
r->nr_accesses = accesses[it][ir];
- r->nr_accesses_bp = accesses[it][ir] * 10000;
damon_add_region(r, t);
}
it++;

@@ -151,7 +150,6 @@ static void damon_test_split_at(struct kunit *test)

damon_free_target(t);
kunit_skip(test, "region alloc fail");
}
- r->nr_accesses_bp = 420000;
r->nr_accesses = 42;
r->last_nr_accesses = 15;
r->age = 10;

@@ -164,7 +162,6 @@ static void damon_test_split_at(struct kunit *test)

KUNIT_EXPECT_EQ(test, r_new->ar.start, 25ul);
KUNIT_EXPECT_EQ(test, r_new->ar.end, 100ul);

- KUNIT_EXPECT_EQ(test, r->nr_accesses_bp, r_new->nr_accesses_bp);
KUNIT_EXPECT_EQ(test, r->nr_accesses, r_new->nr_accesses);
KUNIT_EXPECT_EQ(test, r->last_nr_accesses, r_new->last_nr_accesses);
KUNIT_EXPECT_EQ(test, r->age, r_new->age);

@@ -187,7 +184,6 @@ static void damon_test_merge_two(struct kunit *test)

kunit_skip(test, "region alloc fail");
}
r->nr_accesses = 10;
- r->nr_accesses_bp = 100000;
r->age = 9;
damon_add_region(r, t);
r2 = damon_new_region(100, 300);

@@ -196,7 +192,6 @@ static void damon_test_merge_two(struct kunit *test)

kunit_skip(test, "second region alloc fail");
}
r2->nr_accesses = 20;
- r2->nr_accesses_bp = 200000;
r2->age = 21;
damon_add_region(r2, t);

@@ -204,7 +199,6 @@ static void damon_test_merge_two(struct kunit *test)

KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
KUNIT_EXPECT_EQ(test, r->ar.end, 300ul);
KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u);
- KUNIT_EXPECT_EQ(test, r->nr_accesses_bp, 160000u);
KUNIT_EXPECT_EQ(test, r->age, 17u);

i = 0;

@@ -252,7 +246,6 @@ static void damon_test_merge_regions_of(struct kunit *test)

kunit_skip(test, "region alloc fail");
}
r->nr_accesses = nrs[i];
- r->nr_accesses_bp = nrs[i] * 10000;
damon_add_region(r, t);
}

@@ -615,7 +608,6 @@ static void damon_test_update_monitoring_result(struct kunit *test)

[SJ Park]

On Mon, 29 Jun 2026 21:07:53 -0700 SJ Park <s...@kernel.org> wrote:

> TLDR: Replace damon_region->nr_accesses_bp, which is easy to be wrong,
> with a simpler on-demand moving sum function, damon_nr_accesses_mvsum().

Sashiko found no blocker for this series. All Sashiko findings and my
responses can be found from the complete thread [1] at lore.kernel.org.

It found a typo in the commit message of patch 14, though. I added the detail
about the typo as a reply [2] to the patch. Andrew, could you please fix the
commit message when you pick it up? If you prefer sending a new revision with
the fixup, pleae feel free to let me know.

[1] https://lore.kernel.org/2026063004081...@kernel.org
[2] https://lore.kernel.org/2026063004485...@kernel.org/

Thanks,
SJ

[...]