[RFC PATCH 0/6] mm/damon: introduce probe_hits_wsum DAMOS core filter

[RFC PATCH 0/6] mm/damon: introduce probe_hits_wsum DAMOS core filter

[SJ Park]

DAMON can do flexible data attributes monitoring.  The classical data
access monitoring can also be done using the attributes monitoring.  The
access event is just one of the data attributes that DAMON supports.
Users do monitoring to make some actions based on it.  DAMOS is a
feature for automating that.  However, DAMOS cannot utilize the data
attributes monitoring results.  It is still Data "Access"
Monitoring-based Operation Schemes.  It requires users to set the target
"access" pattern.

DAMOS core filter is effectively the same as the target access pattern.
It is just a more generalized and flexible way of describing the
operation action target region.  Introduce a new DAMOS core filter type,
probe_hits_wsum.  It specifies the filter target based on a range of the
probe hits weighted sum.  Using this, users can apply DAMOS actions to
regions of specific data attributes pattern.

Note that the classic target access pattern still works.  Hence the
target nr_accesses range should still be properly configured.  The new
filter would be used in only data attributes-only mode.  In the mode,
classic access monitoring is just turned off, and therefore nr_accesses
of regions are always zero.  Users could simply set the target
nr_accesses range to include the zero nr_Accesses regions.

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

Patch 1 updates the DAMON kernel API for the new filter type.  Patch 2
implements the filter type in the core layer.  Patch 3 refactor DAMON
sysfs interface internal data structure for efficient reuse of data
structure for the probe hits weighted sum range user inputs.  Patch 4
updates DAMON sysfs interface to support the new filter type.  Patches 5
and 6 update design and usage documents for the new filter type,
respectively.

SJ Park (6):
  mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM
  mm/damon/core: support probe_hits_wsum damos core filter
  mm/damon/sysfs-schemes: rename sysfs_filter->sz_range to
    range_{min,max}
  mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum
    filter
  Docs/mm/damon/design: update for probe_hits_wsum DAMOS core filter
  Docs/admin-guide/mm/damon/usage: update for probe_hits_wsum DAMOS
    filter

 Documentation/admin-guide/mm/damon/usage.rst |  4 +++
 Documentation/mm/damon/design.rst            |  3 ++
 include/linux/damon.h                        |  8 ++++++
 mm/damon/core.c                              | 12 +++++++-
 mm/damon/sysfs-schemes.c                     | 30 ++++++++++++++------
 5 files changed, 48 insertions(+), 9 deletions(-)


base-commit: 787c63ba44ce65021966f55673e27d778c8d9c68
-- 
2.47.3

[RFC PATCH 1/6] mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM

[SJ Park]

Update DAMON kernel API to introduce new DAMOS core filter type,
PROBE_HITS_WSUM.  It will allow API callers to describe the DAMOS action
target regions based on their probe_hits weighted sum.  For describing
the filtering target weighted sum range, add two type-dependent union
fields to damos_filter.

Signed-off-by: SJ Park <sj@kernel.org>
---
 include/linux/damon.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 871d26adf6ae5..59d57131d8327 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -399,6 +399,7 @@ struct damos_stat {
  * @DAMOS_FILTER_TYPE_UNMAPPED:	Unmapped pages.
  * @DAMOS_FILTER_TYPE_ADDR:	Address range.
  * @DAMOS_FILTER_TYPE_TARGET:	Data Access Monitoring target.
+ * @DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:	probe_hits weighted sum range.
  * @NR_DAMOS_FILTER_TYPES:	Number of filter types.
  *
  * All types except &DAMOS_FILTER_TYPE_ADDR and &DAMOS_FILTER_TYPE_TARGET
@@ -420,6 +421,7 @@ enum damos_filter_type {
 	DAMOS_FILTER_TYPE_UNMAPPED,
 	DAMOS_FILTER_TYPE_ADDR,
 	DAMOS_FILTER_TYPE_TARGET,
+	DAMOS_FILTER_TYPE_PROBE_HITS_WSUM,
 	NR_DAMOS_FILTER_TYPES,
 };
 
@@ -434,6 +436,8 @@ enum damos_filter_type {
  *		&damon_ctx->adaptive_targets if @type is
  *		DAMOS_FILTER_TYPE_TARGET.
  * @sz_range:	Size range if @type is DAMOS_FILTER_TYPE_HUGEPAGE_SIZE.
+ * @range_min:	Minimum value of range arguments.
+ * @range_mx:	Maximum value of range arguments.
  *
  * Before applying the &damos->action to a memory region, DAMOS checks if each
  * byte of the region matches to this given condition and avoid applying the
@@ -450,6 +454,10 @@ struct damos_filter {
 		struct damon_addr_range addr_range;
 		int target_idx;
 		struct damon_size_range sz_range;
+		struct {
+			unsigned long range_min;
+			unsigned long range_max;
+		};
 	};
 /* private: */
 	/* List head for siblings. */
-- 
2.47.3

[RFC PATCH 2/6] mm/damon/core: support probe_hits_wsum damos core filter

[SJ Park]

Implement probe_hits_wsum DAMOS core filter support in the core layer.
Make three small changes for the support.  First, update
damos_filter_for_ops() to treat probe_hits_wsum filter as core filter.
Second, Update destination damos_filter->range_{min,max} for
probe_hits_wsum type damos filter commits.  Third, extend
damos_filter_match() to handle probe_hits_wsum type filter. Calculate
the weighted sum of the given region and compare it with the given
filter's target weighted sum range.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/core.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 1752afede01e2..5b976162c5eed 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -654,6 +654,7 @@ bool damos_filter_for_ops(enum damos_filter_type type)
 	switch (type) {
 	case DAMOS_FILTER_TYPE_ADDR:
 	case DAMOS_FILTER_TYPE_TARGET:
+	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
 		return false;
 	default:
 		break;
@@ -1328,6 +1329,10 @@ static void damos_commit_filter_arg(
 	case DAMOS_FILTER_TYPE_HUGEPAGE_SIZE:
 		dst->sz_range = src->sz_range;
 		break;
+	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
+		dst->range_min = src->range_min;
+		dst->range_max = src->range_max;
+		break;
 	default:
 		break;
 	}
@@ -2506,7 +2511,7 @@ static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t,
 	bool matched = false;
 	struct damon_target *ti;
 	int target_idx = 0;
-	unsigned long start, end;
+	unsigned long start, end, wsum;
 
 	switch (filter->type) {
 	case DAMOS_FILTER_TYPE_TARGET:
@@ -2541,6 +2546,11 @@ static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t,
 		damon_split_region_at(t, r, end - r->ar.start);
 		matched = true;
 		break;
+	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
+		wsum = damon_probe_hits_wsum(r, false, ctx);
+		matched = filter->range_min <= wsum &&
+			wsum <= filter->range_max;
+		break;
 	default:
 		return false;
 	}
-- 
2.47.3

[RFC PATCH 3/6] mm/damon/sysfs-schemes: rename sysfs_filter->sz_range to range_{min,max}

[SJ Park]

DAMON sysfs interface provides 'min' and 'max' files under the DAMOS
filter directory.  The purpose is setting the general range arguments
for hugepage_size like filters that require range arguments.  So far,
hugepage_size was the only filter using it.  Hence sz_range field of
damon_sysfs_scheme_filter struct was connected to the files.

In future, we could add a new filter that can reuse the 'min' and 'max'
files.  And the filter might use a range of a type that is not size. For
example, probe_hits weighted sum.  In this case, simply reusing the
sz_range field would make it a little confusing.  Rename sz_range to
range_{min,max} to avoid such confusion.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index d9b81d7b5910e..4d9147d2a269e 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -534,7 +534,8 @@ struct damon_sysfs_scheme_filter {
 	bool allow;
 	char *memcg_path;
 	struct damon_addr_range addr_range;
-	struct damon_size_range sz_range;
+	unsigned long range_min;
+	unsigned long range_max;
 	int target_idx;
 };
 
@@ -588,6 +589,7 @@ damos_sysfs_filter_type_names[] = {
 		.type = DAMOS_FILTER_TYPE_TARGET,
 		.name = "target",
 	},
+
 };
 
 static ssize_t type_show(struct kobject *kobj,
@@ -778,7 +780,7 @@ static ssize_t min_show(struct kobject *kobj,
 	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
 			struct damon_sysfs_scheme_filter, kobj);
 
-	return sysfs_emit(buf, "%lu\n", filter->sz_range.min);
+	return sysfs_emit(buf, "%lu\n", filter->range_min);
 }
 
 static ssize_t min_store(struct kobject *kobj,
@@ -786,7 +788,7 @@ static ssize_t min_store(struct kobject *kobj,
 {
 	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
 			struct damon_sysfs_scheme_filter, kobj);
-	int err = kstrtoul(buf, 0, &filter->sz_range.min);
+	int err = kstrtoul(buf, 0, &filter->range_min);
 
 	return err ? err : count;
 }
@@ -797,7 +799,7 @@ static ssize_t max_show(struct kobject *kobj,
 	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
 			struct damon_sysfs_scheme_filter, kobj);
 
-	return sysfs_emit(buf, "%lu\n", filter->sz_range.max);
+	return sysfs_emit(buf, "%lu\n", filter->range_max);
 }
 
 static ssize_t max_store(struct kobject *kobj,
@@ -805,7 +807,7 @@ static ssize_t max_store(struct kobject *kobj,
 {
 	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
 			struct damon_sysfs_scheme_filter, kobj);
-	int err = kstrtoul(buf, 0, &filter->sz_range.max);
+	int err = kstrtoul(buf, 0, &filter->range_max);
 
 	return err ? err : count;
 }
@@ -2835,12 +2837,13 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
 		} else if (filter->type == DAMOS_FILTER_TYPE_TARGET) {
 			filter->target_idx = sysfs_filter->target_idx;
 		} else if (filter->type == DAMOS_FILTER_TYPE_HUGEPAGE_SIZE) {
-			if (sysfs_filter->sz_range.min >
-					sysfs_filter->sz_range.max) {
+			if (sysfs_filter->range_min >
+					sysfs_filter->range_max) {
 				damos_destroy_filter(filter);
 				return -EINVAL;
 			}
-			filter->sz_range = sysfs_filter->sz_range;
+			filter->sz_range.min = sysfs_filter->range_min;
+			filter->sz_range.max = sysfs_filter->range_max;
 		}
 
 		damos_add_filter(scheme, filter);
-- 
2.47.3

[RFC PATCH 4/6] mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

[SJ Park]

Extend DAMON sysfs interface to support probe_hits_wsum input.  Also
update sysfs input based scheme build logic to setup the min/max probe
hits weighted sum range as user provided.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 4d9147d2a269e..e297a20c0af03 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -589,7 +589,10 @@ damos_sysfs_filter_type_names[] = {
 		.type = DAMOS_FILTER_TYPE_TARGET,
 		.name = "target",
 	},
-
+	{
+		.type = DAMOS_FILTER_TYPE_PROBE_HITS_WSUM,
+		.name = "probe_hits_wsum",
+	},
 };
 
 static ssize_t type_show(struct kobject *kobj,
@@ -2844,6 +2847,14 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
 			}
 			filter->sz_range.min = sysfs_filter->range_min;
 			filter->sz_range.max = sysfs_filter->range_max;
+		} else if (filter->type == DAMOS_FILTER_TYPE_PROBE_HITS_WSUM) {
+			if (sysfs_filter->range_min >
+					sysfs_filter->range_max) {
+				damos_destroy_filter(filter);
+				return -EINVAL;
+			}
+			filter->sz_range.min = sysfs_filter->range_min;
+			filter->sz_range.max = sysfs_filter->range_max;
 		}
 
 		damos_add_filter(scheme, filter);
-- 
2.47.3

[RFC PATCH 5/6] Docs/mm/damon/design: update for probe_hits_wsum DAMOS core filter

[SJ Park]

Update DAMON design document for the newly added probe hits weighted sum
based DAMOS core filter type.

Signed-off-by: SJ Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index aac84de261aa8..8e980dde362de 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -822,6 +822,9 @@ Below ``type`` of filters are currently supported.
         - Applied to pages that belonging to a given address range.
     - target
         - Applied to pages that belonging to a given DAMON monitoring target.
+    - probe_hits_wsum
+        - Matches to monitoring regions having a given range of :ref:`probe
+          hits weighted sum <damon_design_attrs_only_monitoring>` value.
 - Operations layer handled, supported by only ``paddr`` operations set.
     - anon
         - Applied to pages that containing data that not stored in files.
-- 
2.47.3

[RFC PATCH 6/6] Docs/admin-guide/mm/damon/usage: update for probe_hits_wsum DAMOS filter

[SJ Park]

Update DAMON usage document for the newly added probe hits weighted sum
based DAMOS core filter type.

Signed-off-by: SJ Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 023c6334024f8..d3e37400367bd 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -551,6 +551,10 @@ and ``damon_target_idx``.  To ``type`` file, you can write the type of the
 filter.  Refer to :ref:`the design doc <damon_design_damos_filters>` for
 available type names, their meaning and on what layer those are handled.
 
+For ``probe_hits_wsum`` type, you can specify the minimum and maximum probe
+hits weighted sum value for the filter to ``min`` and ``max`` files,
+respectively.
+
 For ``memcg`` type, you can specify the memory cgroup of the interest by
 writing the path of the memory cgroup from the cgroups mount point to
 ``memcg_path`` file.  For ``addr`` type, you can specify the start and end
-- 
2.47.3

Re: [RFC PATCH 5/6] Docs/mm/damon/design: update for probe_hits_wsum DAMOS core filter

[sashiko-bot]

> Update DAMON design document for the newly added probe hits weighted sum
> based DAMOS core filter type.
> 
> Signed-off-by: SJ Park <sj@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=5

Re: [RFC PATCH 3/6] mm/damon/sysfs-schemes: rename sysfs_filter->sz_range to range_{min,max}

[sashiko-bot]

> DAMON sysfs interface provides 'min' and 'max' files under the DAMOS
> filter directory.  The purpose is setting the general range arguments
> for hugepage_size like filters that require range arguments.  So far,
> hugepage_size was the only filter using it.  Hence sz_range field of
> damon_sysfs_scheme_filter struct was connected to the files.
> 
> In future, we could add a new filter that can reuse the 'min' and 'max'
> files.  And the filter might use a range of a type that is not size. For
> example, probe_hits weighted sum.  In this case, simply reusing the
> sz_range field would make it a little confusing.  Rename sz_range to
> range_{min,max} to avoid such confusion.
> 
> Signed-off-by: SJ Park <sj@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=3

Re: [RFC PATCH 6/6] Docs/admin-guide/mm/damon/usage: update for probe_hits_wsum DAMOS filter

[sashiko-bot]

> Update DAMON usage document for the newly added probe hits weighted sum
> based DAMOS core filter type.
> 
> Signed-off-by: SJ Park <sj@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=6

Re: [RFC PATCH 1/6] mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Mismatch between kernel-doc comment and the actual struct field name for range_max.
--

commit 7d0758e3c3054c52a080a43553753f124a5933b1
Author: SJ Park <sj@kernel.org>

mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM

Update DAMON kernel API to introduce new DAMOS core filter type,
PROBE_HITS_WSUM. It adds two type-dependent union fields to damos_filter
for describing the filtering target weighted sum range.

> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index 871d26adf6ae5..59d57131d8327 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
[ ... ]
> @@ -434,6 +436,8 @@ enum damos_filter_type {
>   *		&damon_ctx->adaptive_targets if @type is
>   *		DAMOS_FILTER_TYPE_TARGET.
>   * @sz_range:	Size range if @type is DAMOS_FILTER_TYPE_HUGEPAGE_SIZE.
> + * @range_min:	Minimum value of range arguments.
> + * @range_mx:	Maximum value of range arguments.

[Severity: Low]
This isn't a bug, but there appears to be a typo in the kernel-doc comment
compared to the actual struct field. Should this be @range_max instead of
@range_mx to match the struct field defined below?

>   *
>   * Before applying the &damos->action to a memory region, DAMOS checks if each
>   * byte of the region matches to this given condition and avoid applying the
> @@ -450,6 +454,10 @@ struct damos_filter {
>  		struct damon_addr_range addr_range;
>  		int target_idx;
>  		struct damon_size_range sz_range;
> +		struct {
> +			unsigned long range_min;
> +			unsigned long range_max;
> +		};
>  	};
>  /* private: */
>  	/* List head for siblings. */

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=1

Re: [RFC PATCH 1/6] mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM

[SJ Park]

On Sun, 06 Sep 2026 21:13:01 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] Mismatch between kernel-doc comment and the actual struct field name for range_max.
> --
> 
> commit 7d0758e3c3054c52a080a43553753f124a5933b1
> Author: SJ Park <sj@kernel.org>
> 
> mm/damon/api: introduce DAMOS_FILTER_TYPE_PROBE_HITS_WSUM
> 
> Update DAMON kernel API to introduce new DAMOS core filter type,
> PROBE_HITS_WSUM. It adds two type-dependent union fields to damos_filter
> for describing the filtering target weighted sum range.
> 
> > diff --git a/include/linux/damon.h b/include/linux/damon.h
> > index 871d26adf6ae5..59d57131d8327 100644
> > --- a/include/linux/damon.h
> > +++ b/include/linux/damon.h
> [ ... ]
> > @@ -434,6 +436,8 @@ enum damos_filter_type {
> >   *		&damon_ctx->adaptive_targets if @type is
> >   *		DAMOS_FILTER_TYPE_TARGET.
> >   * @sz_range:	Size range if @type is DAMOS_FILTER_TYPE_HUGEPAGE_SIZE.
> > + * @range_min:	Minimum value of range arguments.
> > + * @range_mx:	Maximum value of range arguments.
> 
> [Severity: Low]
> This isn't a bug, but there appears to be a typo in the kernel-doc comment
> compared to the actual struct field. Should this be @range_max instead of
> @range_mx to match the struct field defined below?

Good catch.  I will fix this in the next revision.

> 
> >   *
> >   * Before applying the &damos->action to a memory region, DAMOS checks if each
> >   * byte of the region matches to this given condition and avoid applying the
> > @@ -450,6 +454,10 @@ struct damos_filter {
> >  		struct damon_addr_range addr_range;
> >  		int target_idx;
> >  		struct damon_size_range sz_range;
> > +		struct {
> > +			unsigned long range_min;
> > +			unsigned long range_max;
> > +		};
> >  	};
> >  /* private: */
> >  	/* List head for siblings. */
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=1


Thanks,
SJ

Re: [RFC PATCH 4/6] mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Incorrect union member assignment for PROBE_HITS_WSUM filter type risks silent corruption if struct layout changes.
--

commit 67e5bf0750883cfdf7b8857b78d72c17c2de406e
Author: SJ Park <sj@kernel.org>

mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

This commit extends the DAMON sysfs interface to support probe_hits_wsum
input. It updates the sysfs input based scheme build logic to set up the
min/max probe hits weighted sum range provided by the user.

> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index 4d9147d2a269e..e297a20c0af03 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c

[ ... ]

> @@ -2844,6 +2847,14 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
>  			}
>  			filter->sz_range.min = sysfs_filter->range_min;
>  			filter->sz_range.max = sysfs_filter->range_max;
> +		} else if (filter->type == DAMOS_FILTER_TYPE_PROBE_HITS_WSUM) {
> +			if (sysfs_filter->range_min >
> +					sysfs_filter->range_max) {
> +				damos_destroy_filter(filter);
> +				return -EINVAL;
> +			}
> +			filter->sz_range.min = sysfs_filter->range_min;
> +			filter->sz_range.max = sysfs_filter->range_max;

[Severity: Low]
Is this assigning to the wrong union member? Since the filter type is
DAMOS_FILTER_TYPE_PROBE_HITS_WSUM, should this be assigning directly to
filter->range_min and filter->range_max instead of filter->sz_range?

While struct damon_size_range and the anonymous { unsigned long range_min;
unsigned long range_max; } struct currently share the exact same memory layout
in the struct damos_filter union, using sz_range here appears to be a
copy-paste error from the DAMOS_FILTER_TYPE_HUGEPAGE_SIZE block.

This seems to bypass the earlier refactoring that explicitly introduced
the anonymous struct to avoid reusing sz_range for non-size fields. If
struct damon_size_range is modified in the future, assigning via sz_range
while the core logic consumes range_min could lead to silent data corruption
when building a PROBE_HITS_WSUM scheme filter.

>  		}
>  
>  		damos_add_filter(scheme, filter);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=4

Re: [RFC PATCH 2/6] mm/damon/core: support probe_hits_wsum damos core filter

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] DAMOS_FILTER_TYPE_PROBE_HITS_WSUM uses raw, unscaled probe hits instead of a moving sum, leading to inaccurate filter evaluation when apply_interval is smaller than aggr_interval.
--

commit 75c1f2781e8de8f015329fce3e8a8d40e521f7de
Author: SJ Park <sj@kernel.org>

mm/damon/core: support probe_hits_wsum damos core filter

This commit implements the probe_hits_wsum DAMOS core filter support. It
updates damos_filter_for_ops, handles the range parameters during filter
commits, and calculates the weighted sum of probe hits for filter matching.

> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index ce8c6f99106ed..ec1a1666aa9cc 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c

[ ... ]

> @@ -2538,6 +2543,11 @@ static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t,
>  		damon_split_region_at(t, r, end - r->ar.start);
>  		matched = true;
>  		break;
> +	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
> +		wsum = damon_probe_hits_wsum(r, false, ctx);
> +		matched = filter->range_min <= wsum &&
> +			wsum <= filter->range_max;

[Severity: Medium]
When a scheme's apply_interval_us is smaller than its aggr_interval_us, does
this evaluate incomplete probe hits?

Because the probe_hits array accumulates from zero over the aggregation
interval, evaluating the raw probe hits mid-interval yields artificially low
values. This differs from access pattern evaluations, which scale the count
based on the elapsed fraction of the aggregation interval (for example, using
damon_nr_accesses_mvsum()).

Could this cause regions to incorrectly fail or falsely match the filter
depending on when the scheme is evaluated within the aggregation interval?

> +		break;
>  	default:
>  		return false;
>  	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=2

Re: [RFC PATCH 2/6] mm/damon/core: support probe_hits_wsum damos core filter

[SJ Park]

On Sun, 06 Sep 2026 21:17:53 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] DAMOS_FILTER_TYPE_PROBE_HITS_WSUM uses raw, unscaled probe hits instead of a moving sum, leading to inaccurate filter evaluation when apply_interval is smaller than aggr_interval.
> --
> 
> commit 75c1f2781e8de8f015329fce3e8a8d40e521f7de
> Author: SJ Park <sj@kernel.org>
> 
> mm/damon/core: support probe_hits_wsum damos core filter
> 
> This commit implements the probe_hits_wsum DAMOS core filter support. It
> updates damos_filter_for_ops, handles the range parameters during filter
> commits, and calculates the weighted sum of probe hits for filter matching.
> 
> > diff --git a/mm/damon/core.c b/mm/damon/core.c
> > index ce8c6f99106ed..ec1a1666aa9cc 100644
> > --- a/mm/damon/core.c
> > +++ b/mm/damon/core.c
> 
> [ ... ]
> 
> > @@ -2538,6 +2543,11 @@ static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t,
> >  		damon_split_region_at(t, r, end - r->ar.start);
> >  		matched = true;
> >  		break;
> > +	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
> > +		wsum = damon_probe_hits_wsum(r, false, ctx);
> > +		matched = filter->range_min <= wsum &&
> > +			wsum <= filter->range_max;
> 
> [Severity: Medium]
> When a scheme's apply_interval_us is smaller than its aggr_interval_us, does
> this evaluate incomplete probe hits?
> 
> Because the probe_hits array accumulates from zero over the aggregation
> interval, evaluating the raw probe hits mid-interval yields artificially low
> values. This differs from access pattern evaluations, which scale the count
> based on the elapsed fraction of the aggregation interval (for example, using
> damon_nr_accesses_mvsum()).
> 
> Could this cause regions to incorrectly fail or falsely match the filter
> depending on when the scheme is evaluated within the aggregation interval?

Good catch.  I will extend damon_probe_hits_wsum() to provide moving sum based
weighted sum, and use it in the next revision.

> 
> > +		break;
> >  	default:
> >  		return false;
> >  	}
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=2
> 


Thanks,
SJ

Re: [RFC PATCH 4/6] mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

[SJ Park]

On Sun, 06 Sep 2026 21:16:17 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] Incorrect union member assignment for PROBE_HITS_WSUM filter type risks silent corruption if struct layout changes.
> --
> 
> commit 67e5bf0750883cfdf7b8857b78d72c17c2de406e
> Author: SJ Park <sj@kernel.org>
> 
> mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter
> 
> This commit extends the DAMON sysfs interface to support probe_hits_wsum
> input. It updates the sysfs input based scheme build logic to set up the
> min/max probe hits weighted sum range provided by the user.
> 
> > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> > index 4d9147d2a269e..e297a20c0af03 100644
> > --- a/mm/damon/sysfs-schemes.c
> > +++ b/mm/damon/sysfs-schemes.c
> 
> [ ... ]
> 
> > @@ -2844,6 +2847,14 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
> >  			}
> >  			filter->sz_range.min = sysfs_filter->range_min;
> >  			filter->sz_range.max = sysfs_filter->range_max;
> > +		} else if (filter->type = DAMOS_FILTER_TYPE_PROBE_HITS_WSUM) {
> > +			if (sysfs_filter->range_min >
> > +					sysfs_filter->range_max) {
> > +				damos_destroy_filter(filter);
> > +				return -EINVAL;
> > +			}
> > +			filter->sz_range.min = sysfs_filter->range_min;
> > +			filter->sz_range.max = sysfs_filter->range_max;
> 
> [Severity: Low]
> Is this assigning to the wrong union member? Since the filter type is
> DAMOS_FILTER_TYPE_PROBE_HITS_WSUM, should this be assigning directly to
> filter->range_min and filter->range_max instead of filter->sz_range?
> 
> While struct damon_size_range and the anonymous { unsigned long range_min;
> unsigned long range_max; } struct currently share the exact same memory layout
> in the struct damos_filter union, using sz_range here appears to be a
> copy-paste error from the DAMOS_FILTER_TYPE_HUGEPAGE_SIZE block.
> 
> This seems to bypass the earlier refactoring that explicitly introduced
> the anonymous struct to avoid reusing sz_range for non-size fields. If
> struct damon_size_range is modified in the future, assigning via sz_range
> while the core logic consumes range_min could lead to silent data corruption
> when building a PROBE_HITS_WSUM scheme filter.

Good catch.  I will fix this in the next revision

> 
> >  		}
> >  
> >  		damos_add_filter(scheme, filter);
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=4
> 


Thanks,
SJ