[RFC PATCH 08/18] mm/damon/core: implement per-scheme filter-passed bytes stat

[SeongJae Park <sj@xxxxxxxxxx>]

Implement a new per-DAMOS scheme statistic field, namely
sz_ops_filter_passed, using the changed damon_operations->apply_scheme()
interface.  It counts total bytes of memory that given DAMOS action
tried to be applied, and passed the filters of the scheme.  DAMON API
users can access it using DAMON-internal safe access features such as
damon_call() and/or damos_walk().

Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 include/linux/damon.h | 3 +++
 mm/damon/core.c       | 6 ++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index bff39c23f16e..4a68bb38aad5 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -291,6 +291,8 @@ struct damos_watermarks {
  * @sz_tried:	Total size of regions that the scheme is tried to be applied.
  * @nr_applied:	Total number of regions that the scheme is applied.
  * @sz_applied:	Total size of regions that the scheme is applied.
+ * @sz_ops_filter_passed:
+ * 		Total bytes that passed ops layer-handled DAMOS filters.
  * @qt_exceeds: Total number of times the quota of the scheme has exceeded.
  *
  * "Tried an action to a region" in this context means the DAMOS core logic
@@ -315,6 +317,7 @@ struct damos_stat {
 	unsigned long sz_tried;
 	unsigned long nr_applied;
 	unsigned long sz_applied;
+	unsigned long sz_ops_filter_passed;
 	unsigned long qt_exceeds;
 };
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index c7ae95d6b7ba..8540e8f91260 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1354,13 +1354,15 @@ static bool damos_skip_charged_region(struct damon_target *t,
 }
 
 static void damos_update_stat(struct damos *s,
-		unsigned long sz_tried, unsigned long sz_applied)
+		unsigned long sz_tried, unsigned long sz_applied,
+		unsigned long sz_ops_filter_passed)
 {
 	s->stat.nr_tried++;
 	s->stat.sz_tried += sz_tried;
 	if (sz_applied)
 		s->stat.nr_applied++;
 	s->stat.sz_applied += sz_applied;
+	s->stat.sz_ops_filter_passed += sz_ops_filter_passed;
 }
 
 static bool __damos_filter_out(struct damon_ctx *ctx, struct damon_target *t,
@@ -1580,7 +1582,7 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
 		r->age = 0;
 
 update_stat:
-	damos_update_stat(s, sz, sz_applied);
+	damos_update_stat(s, sz, sz_applied, sz_ops_filter_passed);
 }
 
 static void damon_do_apply_schemes(struct damon_ctx *c,
-- 
2.39.5