From cfe9e8c738d9acfa09973040e2dfa3fbd17c12be Mon Sep 17 00:00:00 2001
From: SJ Park <sj@kernel.org>
Date: Fri, 10 Jul 2026 06:46:34 -0700
Subject: [PATCH] mm/damon/core: implement damon_probe_hits_wsum()

When damon_probe->weight is set, the weighted sum of probe hits will be
useful.  It will be useful for not only the users but also DAMON internal
logics like regions merging.  Implement a function for calculating it.

Link: https://lore.kernel.org/20260710134651.18084-6-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>
---
 include/linux/damon.h |  2 ++
 mm/damon/core.c       | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index e7acd8e610a6..f69442a9d431 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -1012,6 +1012,8 @@ unsigned int damon_nr_accesses_mvsum(struct damon_region *r,
 		struct damon_ctx *ctx);
 unsigned char damon_probe_hits_mvsum(int probe_idx, struct damon_region *r,
 		struct damon_ctx *ctx);
+unsigned int damon_probe_hits_wsum(struct damon_region *r, bool last,
+		struct damon_ctx *ctx);
 
 int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
 		unsigned int nr_ranges, unsigned long min_region_sz);
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 9f6cdd810bd8..fea97399b575 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -393,6 +393,30 @@ static bool damon_is_last_region(struct damon_region *r,
 	return list_is_last(&r->list, &t->regions_list);
 }
 
+/**
+ * damon_probe_hits_wsum() - Returns probe hits weighted sum of a region.
+ * @r:		region to get the weighted sum of.
+ * @last:	if the request is for last-window aggregated probe hits.
+ * @ctx:	context of &r.
+ *
+ * Return: the weighted sum of probe hits of the region.
+ */
+unsigned int damon_probe_hits_wsum(struct damon_region *r, bool last,
+		struct damon_ctx *ctx)
+{
+	struct damon_probe *probe;
+	unsigned int sum = 0;
+	int i = 0;
+
+	damon_for_each_probe(probe, ctx) {
+		if (last)
+			sum += r->last_probe_hits[i++] * probe->weight;
+		else
+			sum += r->probe_hits[i++] * probe->weight;
+	}
+	return sum;
+}
+
 /*
  * Check whether a region is intersecting an address range
  *