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mm/damon/core: copy nr_accesses when splitting region

PATCH Applied SeongJae Park 1 participant 2 messages Nov 19, 2023

Subsystems (3)
Memory management Kselftest DAMON
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SeongJae Park

author maintainer
#0 lore raw

PATCH 1/2 mm/damon/core: copy nr_accesses when splitting region

Regions split function ('damon_split_region_at()') is called at the beginning of an aggregation interval, and when DAMOS applying the actions and charging quota. Because 'nr_accesses' fields of all regions are reset at the beginning of each aggregation interval, and DAMOS was applying the action at the end of each aggregation interval, there was no need to copy the 'nr_accesses' field to the split-out region.

However, commit 42f994b71404 ("mm/damon/core: implement scheme-specific apply interval") made DAMOS applies action on its own timing interval. Hence, 'nr_accesses' should also copied to split-out regions, but the commit didn't. Fix it by copying it.

Fixes 42f994b71404 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by SeongJae Park <[email protected]>

---
Cc-ing stable@ is not needed, since the commit that introduced the issue has merged in v6.7 merge window.

 mm/damon/core.c | 1 +
 1 file changed, 1 insertion(+)
mm/damon/core.c +1 -0
index 6262d55904e7..ce1562783e7e 100644
@@ -1225,6 +1225,7 @@ 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;
+	new->nr_accesses = r->nr_accesses;
 
 	damon_insert_region(new, r, damon_next_region(r), t);
 }
Signature · 1 line
2.34.1
author maintainer
#1 lore raw

PATCH 2/2 mm/damon/core-test: test damon_split_region_at()'s access rate copying

damon_split_region_at() should set access rate related fields of the resulting regions same. It may forgotten, and actually there was the mistake before. Test it with the unit test case for the function.

Signed-off-by SeongJae Park <[email protected]>
---
 mm/damon/core-test.h | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
mm/damon/core-test.h +11 -4
index 649adf91ebc5..e6a01ea2ec54 100644
@@ -122,18 +122,25 @@ static void damon_test_split_at(struct kunit *test)
 {
 	struct damon_ctx *c = damon_new_ctx();
 	struct damon_target *t;
-	struct damon_region *r;
+	struct damon_region *r, *r_new;
 
 	t = damon_new_target();
 	r = damon_new_region(0, 100);
+	r->nr_accesses_bp = 420000;
+	r->nr_accesses = 42;
+	r->last_nr_accesses = 15;
 	damon_add_region(r, t);
 	damon_split_region_at(t, r, 25);
 	KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
 	KUNIT_EXPECT_EQ(test, r->ar.end, 25ul);
 
-	r = damon_next_region(r);
-	KUNIT_EXPECT_EQ(test, r->ar.start, 25ul);
-	KUNIT_EXPECT_EQ(test, r->ar.end, 100ul);
+	r_new = damon_next_region(r);
+	KUNIT_EXPECT_EQ(test, r_new->ar.start, 25ul);
+	KUNIT_EXPECT_EQ(test, r_new->ar.end, 100ul);
+
+	KUNIT_EXPECT_EQ(test, r->nr_accesses_bp, r_new->nr_accesses_bp);
+	KUNIT_EXPECT_EQ(test, r->nr_accesses, r_new->nr_accesses);
+	KUNIT_EXPECT_EQ(test, r->last_nr_accesses, r_new->last_nr_accesses);
 
 	damon_free_target(t);
 	damon_destroy_ctx(c);
Signature · 1 line
2.34.1