mm/damon/core: introduce nr_accesses_bp

Add yet another representation of the access rate of each region, namely
nr_accesses_bp.  It is just same to the nr_accesses but represents the
value in basis point (1 in 10,000), and updated at once in every
aggregation interval.  That is, moving_accesses_bp is just nr_accesses *
10000.  This may seems useless at the moment.  However, it will be useful
for representing less than one nr_accesses value that will be needed to
make moving sum-based nr_accesses.

Link: https://lkml.kernel.org/r/20230915025251.72816-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 11 insertions, 0 deletions

diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
index c539f0e8377e..79f1f12e0dd5 100644
--- a/mm/damon/core-test.h
+++ b/mm/damon/core-test.h
@@ -94,6 +94,7 @@ static void damon_test_aggregate(struct kunit *test)
 		for (ir = 0; ir < 3; ir++) {
 			r = damon_new_region(saddr[it][ir], eaddr[it][ir]);
 			r->nr_accesses = accesses[it][ir];
+			r->nr_accesses_bp = accesses[it][ir] * 10000;
 			damon_add_region(r, t);
 		}
 		it++;
@@ -147,9 +148,11 @@ static void damon_test_merge_two(struct kunit *test)
 	t = damon_new_target();
 	r = damon_new_region(0, 100);
 	r->nr_accesses = 10;
+	r->nr_accesses_bp = 100000;
 	damon_add_region(r, t);
 	r2 = damon_new_region(100, 300);
 	r2->nr_accesses = 20;
+	r2->nr_accesses_bp = 200000;
 	damon_add_region(r2, t);
 
 	damon_merge_two_regions(t, r, r2);
@@ -196,6 +199,7 @@ static void damon_test_merge_regions_of(struct kunit *test)
 	for (i = 0; i < ARRAY_SIZE(sa); i++) {
 		r = damon_new_region(sa[i], ea[i]);
 		r->nr_accesses = nrs[i];
+		r->nr_accesses_bp = nrs[i] * 10000;
 		damon_add_region(r, t);
 	}
 
@@ -297,6 +301,7 @@ static void damon_test_update_monitoring_result(struct kunit *test)
 	struct damon_region *r = damon_new_region(3, 7);
 
 	r->nr_accesses = 15;
+	r->nr_accesses_bp = 150000;
 	r->age = 20;
 
 	new_attrs = (struct damon_attrs){
diff --git a/mm/damon/core.c b/mm/damon/core.c
index b005dc15009f..ce85c00b0a4c 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -128,6 +128,7 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 	region->ar.start = start;
 	region->ar.end = end;
 	region->nr_accesses = 0;
+	region->nr_accesses_bp = 0;
 	INIT_LIST_HEAD(&region->list);
 
 	region->age = 0;
@@ -508,6 +509,7 @@ static void damon_update_monitoring_result(struct damon_region *r,
 {
 	r->nr_accesses = damon_nr_accesses_for_new_attrs(r->nr_accesses,
 			old_attrs, new_attrs);
+	r->nr_accesses_bp = r->nr_accesses * 10000;
 	r->age = damon_age_for_new_attrs(r->age, old_attrs, new_attrs);
 }
 
@@ -1115,6 +1117,7 @@ static void damon_merge_two_regions(struct damon_target *t,
 
 	l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
 			(sz_l + sz_r);
+	l->nr_accesses_bp = l->nr_accesses * 10000;
 	l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r);
 	l->ar.end = r->ar.end;
 	damon_destroy_region(r, t);
@@ -1138,6 +1141,8 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
 		else
 			r->age++;
 
+		r->nr_accesses_bp = r->nr_accesses * 10000;
+
 		if (prev && prev->ar.end == r->ar.start &&
 		    abs(prev->nr_accesses - r->nr_accesses) <= thres &&
 		    damon_sz_region(prev) + damon_sz_region(r) <= sz_limit)
@@ -1186,6 +1191,7 @@ static void damon_split_region_at(struct damon_target *t,
 
 	new->age = r->age;
 	new->last_nr_accesses = r->last_nr_accesses;
+	new->nr_accesses_bp = r->nr_accesses_bp;
 
 	damon_insert_region(new, r, damon_next_region(r), t);
 }