[RFC PATCH 1/3] mm/damon: add damon_region->last_probe_hits

[SeongJae Park <sj@kernel.org>]

Add new damon_region filed, last_probe_hits.  Maintain fully accumulated
probe_hits values from the last aggregation interval in the field.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h |  2 +-
 mm/damon/core.c       | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index fc3d467dc2e34..f0dd45ca788f5 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -70,10 +70,10 @@ struct damon_region {
 	unsigned int nr_accesses;
 	unsigned char probe_hits[DAMON_MAX_PROBES];
 	struct list_head list;
-
 	unsigned int age;
 /* private: Internal value for age calculation. */
 	unsigned int last_nr_accesses;
+	unsigned char last_probe_hits[DAMON_MAX_PROBES];
 };
 
 /**
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 4f7954b383d18..e84f2f1b07cc6 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -304,8 +304,10 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 	region->ar.start = start;
 	region->ar.end = end;
 	region->nr_accesses = 0;
-	for (i = 0; i < DAMON_MAX_PROBES; i++)
+	for (i = 0; i < DAMON_MAX_PROBES; i++) {
 		region->probe_hits[i] = 0;
+		region->last_probe_hits[i] = 0;
+	}
 	INIT_LIST_HEAD(&region->list);
 
 	region->age = 0;
@@ -2024,8 +2026,10 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 					damon_nr_regions(t), nr_probes);
 			r->last_nr_accesses = r->nr_accesses;
 			r->nr_accesses = 0;
-			for (i = 0; i < DAMON_MAX_PROBES; i++)
+			for (i = 0; i < DAMON_MAX_PROBES; i++) {
+				r->last_probe_hits[i] = r->probe_hits[i];
 				r->probe_hits[i] = 0;
+			}
 		}
 		ti++;
 	}
@@ -3216,6 +3220,8 @@ static void damon_split_region_at(struct damon_target *t,
 	new->nr_accesses = r->nr_accesses;
 	/* todo: do this for only installed probes */
 	memcpy(new->probe_hits, r->probe_hits, sizeof(r->probe_hits));
+	memcpy(new->last_probe_hits, r->last_probe_hits,
+			sizeof(r->last_probe_hits));
 
 	damon_insert_region(new, r, damon_next_region(r), t);
 }
-- 
2.47.3