+ mm-damon-core-extend-merge-function-to-work-with-probe-hits.patch added to mm-new branch

+ mm-damon-core-extend-merge-function-to-work-with-probe-hits.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/core: extend merge function to work with probe hits
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-core-extend-merge-function-to-work-with-probe-hits.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-extend-merge-function-to-work-with-probe-hits.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

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: SJ Park <sj@kernel.org>
Subject: mm/damon/core: extend merge function to work with probe hits
Date: Fri, 10 Jul 2026 06:46:37 -0700

When probe weights are set, users may want DAMON monitoring results to be
optimized for the weights.  For that, regions adjustment should work for
the weighted sum of probe hits.  Extend damon_merge_regions_of() to detect
if the weights are set, and work with probe hits in the case.

The weights setup detection function is incomplete.  It always returns
false.  It is intentional, so that more changes to completely support
weights can be made in an incremental but safe way.  Until the function is
completed, all changes depend on it is no-op, so DAMON works in the
current mode.

Link: https://lore.kernel.org/20260710134651.18084-9-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/core.c             |   49 +++++++++++++++++++++++++++-------
 mm/damon/tests/core-kunit.h |   13 +++++++--
 2 files changed, 50 insertions(+), 12 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-extend-merge-function-to-work-with-probe-hits
+++ a/mm/damon/core.c
@@ -209,6 +209,11 @@ static struct damon_probe *damon_nth_pro
 	return NULL;
 }
 
+static bool damon_has_probe_weights(struct damon_ctx *c)
+{
+	return false;
+}
+
 /*
  * damon_mvsum() - Returns pseudo moving sum value for a time window.
  * @current_nr:		The value of the current aggregation window.
@@ -3248,6 +3253,16 @@ static void damon_merge_two_regions(stru
 	damon_destroy_region(r, t);
 }
 
+static unsigned int damon_merge_score(struct damon_region *r, bool last,
+		struct damon_ctx *ctx, bool use_probe_hits)
+{
+	if (use_probe_hits)
+		return damon_probe_hits_wsum(r, last, ctx);
+	if (last)
+		return r->last_nr_accesses;
+	return r->nr_accesses;
+}
+
 /*
  * Merge adjacent regions having similar access frequencies
  *
@@ -3256,24 +3271,38 @@ static void damon_merge_two_regions(stru
  * sz_limit	size upper limit of each region
  */
 static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
-				   unsigned long sz_limit)
+		unsigned long sz_limit, struct damon_ctx *ctx)
 {
 	struct damon_region *r, *prev = NULL, *next;
+	bool use_probe_hits = damon_has_probe_weights(ctx);
 
 	damon_for_each_region_safe(r, next, t) {
-		if (abs_diff(r->nr_accesses, r->last_nr_accesses) > thres)
+		unsigned int score, last_score, diff;
+
+		score = damon_merge_score(r, false, ctx, use_probe_hits);
+		last_score = damon_merge_score(r, true, ctx, use_probe_hits);
+
+		if (abs_diff(score, last_score) > thres)
 			r->age = 0;
-		else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0))
+		else if ((score == 0) != (last_score == 0))
 			r->age = 0;
 		else
 			r->age++;
 
-		if (prev && prev->ar.end == r->ar.start &&
-		    abs_diff(prev->nr_accesses, r->nr_accesses) <= thres &&
-		    damon_sz_region(prev) + damon_sz_region(r) <= sz_limit)
-			damon_merge_two_regions(t, prev, r);
-		else
-			prev = r;
+		if (!prev)
+			goto set_prev_continue;
+		if (prev->ar.end != r->ar.start)
+			goto set_prev_continue;
+		diff = abs_diff(score, damon_merge_score(prev, false, ctx,
+					use_probe_hits));
+		if (diff > thres)
+			goto set_prev_continue;
+		if (damon_sz_region(prev) + damon_sz_region(r) > sz_limit)
+			goto set_prev_continue;
+		damon_merge_two_regions(t, prev, r);
+		continue;
+set_prev_continue:
+		prev = r;
 	}
 }
 
@@ -3306,7 +3335,7 @@ static void kdamond_merge_regions(struct
 	do {
 		nr_regions = 0;
 		damon_for_each_target(t, c) {
-			damon_merge_regions_of(t, threshold, sz_limit);
+			damon_merge_regions_of(t, threshold, sz_limit, c);
 			nr_regions += damon_nr_regions(t);
 		}
 		threshold = max(1, threshold * 2);
--- a/mm/damon/tests/core-kunit.h~mm-damon-core-extend-merge-function-to-work-with-probe-hits
+++ a/mm/damon/tests/core-kunit.h
@@ -226,6 +226,7 @@ static struct damon_region *__nth_region
 
 static void damon_test_merge_regions_of(struct kunit *test)
 {
+	struct damon_ctx *ctx;
 	struct damon_target *t;
 	struct damon_region *r;
 	unsigned long sa[] = {0, 100, 114, 122, 130, 156, 170, 184, 230};
@@ -236,20 +237,27 @@ static void damon_test_merge_regions_of(
 	unsigned long eaddrs[] = {112, 130, 156, 170, 230, 10170};
 	int i;
 
+	ctx = damon_new_ctx();
+	if (!ctx)
+		kunit_skip(test, "ctx alloc fail");
+
 	t = damon_new_target();
-	if (!t)
+	if (!t) {
+		damon_destroy_ctx(ctx);
 		kunit_skip(test, "target alloc fail");
+	}
 	for (i = 0; i < ARRAY_SIZE(sa); i++) {
 		r = damon_new_region(sa[i], ea[i]);
 		if (!r) {
 			damon_free_target(t);
+			damon_destroy_ctx(ctx);
 			kunit_skip(test, "region alloc fail");
 		}
 		r->nr_accesses = nrs[i];
 		damon_add_region(r, t);
 	}
 
-	damon_merge_regions_of(t, 9, 9999);
+	damon_merge_regions_of(t, 9, 9999, ctx);
 	/* 0-112, 114-130, 130-156, 156-170, 170-230, 230-10170 */
 	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 6u);
 	for (i = 0; i < 6; i++) {
@@ -258,6 +266,7 @@ static void damon_test_merge_regions_of(
 		KUNIT_EXPECT_EQ(test, r->ar.end, eaddrs[i]);
 	}
 	damon_free_target(t);
+	damon_destroy_ctx(ctx);
 }
 
 static void damon_test_split_regions_of(struct kunit *test)
_

Patches currently in -mm which might be from sj@kernel.org are

samples-damon-wsse-handle-damon_start-failure.patch
samples-damon-prcl-handle-damon_start-failure.patch
samples-damon-mtier-handle-damon_start-failure.patch
samples-damon-mtier-handle-damon_stop-failure.patch
samples-damon-wsse-stop-and-free-damon-ctx-when-damon_call-fails.patch
samples-damon-prcl-stop-and-free-damon-ctx-when-damon_call-fails.patch
mm-damon-sysfs-kobject_del-target-normal-context-and-kdamond-dirs.patch
mm-damon-sysfs-kobject_del-region-and-target-error-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-region-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-filter-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-quota-goal-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-action-destination-dirs.patch
mm-damon-sysfs-kobject_del-probe-dirs.patch
mm-damon-sysfs-kobject_del-probe-filter-dirs.patch
mm-damon-sysfs-kobject_del-probe-dirs-in-probes_addd_dir-error-path.patch
mm-damon-sysfs-schemes-kobject_del-region-for-populate_region-error.patch
docs-mm-damon-design-update-for-damos_quota_node_eligible_mem_bp.patch
docs-abi-damon-document-probe-files.patch
mm-damon-tests-core-kunit-test-damon_rand.patch
selftests-damon-sysfssh-test-multiple-probe-dirs-creation.patch
selftests-damon-sysfssh-test-coreops_filters-directories.patch
selftests-damon-sysfssh-test-dests-dir.patch
selftests-damon-sysfssh-test-all-files-in-quota-goal-dir.patch
mm-damon-core-reduce-range-setup-in-damon_commit_target_regions.patch
mm-damon-sysfs-split-probe-setup-function-out.patch
mm-damon-sysfs-split-out-filters-setup-function.patch
mm-damon-sysfs-fix-typos-in-probe_addrm_dirs-s-attr-probe.patch
mm-damon-core-introduce-damon_nr_accesses_mvsum.patch
mm-damon-tests-core-kunit-test-damon_mvsum.patch
mm-damon-core-always-update-last_nr_accesses-for-intervals-change.patch
mm-damon-core-handle-unreset-nr_accesses-in-damon_nr_accesses_mvsum.patch
mm-damon-core-use-damon_nr_accesses_mvsum-in-__damos_valid_target.patch
mm-damon-core-use-damon_nr_accesses_mvsum-for-damos-region-tracing.patch
mm-damon-sysfs-schemes-use-damon_nr_accesses_mvsum-for-damo-regions.patch
mm-damon-core-remove-damon_warn_fix_nr_accesses_corruption.patch
mm-damon-core-remove-damon_verify_reset_aggregated.patch
mm-damon-core-remove-damon_verify_merge_regions_of.patch
mm-damon-tests-core-kunit-remove-nr_accesses_bp-setup-and-tests.patch
selftests-damon-drgn_dump_damon_status-do-not-dump-nr_accesses_bp.patch
mm-damon-core-remove-nr_accesses_bp-setups-and-updates.patch
mm-damon-core-remove-attrs-param-from-damon_update_region_access_rate.patch
mm-damon-paddr-remove-attrs-param-from-__damon_pa_check_access.patch
mm-damon-vaddr-remove-attrs-param-from-__damon_va_check_access.patch
mm-damon-core-remove-damon_moving_sum-and-its-unit-test.patch
mm-damon-core-remove-damon_region-nr_accesses_bp.patch
mm-damon-add-damon_region-last_probe_hits.patch
mm-damon-core-introduce-damon_probe_hits_mvsum.patch
mm-damon-sysfs-schemes-set-probe-hits-as-pseudo-moving-sums.patch
mm-damon-core-safely-validate-src-on-damon_commit_ctx.patch
mm-damon-core-do-parameter-testing-commit-on-damon_start.patch
mm-damon-sysfs-remove-duplicated-commit-input-validity-check.patch
mm-damon-reclaim-remove-duplicated-min_region_sz-power-of-2-check.patch
mm-damon-lru_sort-remove-duplicated-min_region_sz-power_of_2-check.patch
mm-damon-document-region-size-validation-in-damon_set_regions.patch
mm-damon-core-remove-start-end-check-in-damon_set_region_system_rams.patch
mm-damon-sysfs-remove-region-size-validation.patch
mm-damon-core-stop-ctxs-in-damon_start-before-returning-an-error.patch
samples-damon-mtier-do-not-stop-first-context-for-damon_start-failure.patch
mm-damon-core-make-damon_stop-never-fails.patch
mm-damon-sysfs-ignore-damon_stop-return-value.patch
mm-damon-reclaaim-ignore-damon_stop-return-value.patch
mm-damon-lru_sort-ignore-damon_stop-return-value.patch
mm-damon-core-change-damon_stop-return-type-to-void.patch
samples-damon-mtier-stop-all-contexts-with-single-damon_stop-call.patch
mm-damon-core-wait-ctx-stop-in-damon_call-before-reruning-an-error.patch
samples-damon-wsse-do-not-stop-ctx-for-damon_call-failure.patch
samples-damon-prcl-do-not-stop-damon-for-damon_call-failure.patch
mm-damon-core-remove-comment-and-test-for-nr_to_bp-divide-by-zero.patch
mm-damon-core-s-damon_max_nr_accesses-damon_nr_samples_per_aggr.patch
mm-damon-core-s-accesses_bp_to_nr_accesses-sample_bp_to_count.patch
mm-damon-core-s-nr_accesses_to_accesses_bp-sample_count_to_bp.patch
mm-damon-core-s-nr_accesses_for_new_attrs-nr_samples_for_new_attrs.patch
mm-damon-core-update-probe-hits-for-new-parameter-commit.patch
mm-damon-core-handle-unreset-probe_hits-in-probe_hits_mvsum.patch
mm-damon-core-introduce-damon_probe-weight.patch
mm-damon-core-ask-apply_probes-ops-callback-to-set-sampling-address.patch
mm-damon-paddr-set-samples-in-apply_probes-if-requested.patch
mm-damon-core-ask-apply_probe-to-return-max-probe-hits-weighted-sum.patch
mm-damon-core-implement-damon_probe_hits_wsum.patch
mm-damon-paddr-respect-return_max_wsum.patch
mm-damon-core-use-abs_diff-instead-of-abs.patch
mm-damon-core-extend-merge-function-to-work-with-probe-hits.patch
mm-damon-core-disallow-probe_hits-overflow-on-attrs-only-monitoring.patch
mm-damon-core-validate-params-for-probe-hits-weighted-sum-overflow.patch
mm-damon-core-disable-access-monitoring-when-probe-weights-are-set.patch
mm-damon-core-set-samples-in-apply_probes-if-probe-weights-are-set.patch
mm-damon-core-s-max_nr_accesses-max_merge_score-in-kdamond_fn.patch
mm-damon-core-get-merge-threshold-from-probe-hits-when-weights-are-set.patch
mm-damon-core-implement-damon_has_probe_weight.patch
mm-damon-sysfs-implement-probe-weight-file.patch
docs-mm-damon-design-document-attrs-only-monitoring.patch
docs-admin-guide-mm-damon-usage-document-weight-sysfs-file.patch
docs-abi-damon-document-probe-weight-file.patch