mm/damon/core: add multiple goals per damos_quota and helpers for those

The feedback-driven DAMOS quota auto-tuning feature allows only single
goal to the DAMON kernel API users.  The API users could implement
multiple goals for the end-users on their level, and that's what DAMON
sysfs interface is doing.  More DAMON kernel API users such as
DAMON_RECLAIM would need to do similar work.  To reduce unnecessary future
duplciated efforts, support multiple goals from DAMOS core layer.  To make
the support in minimum non-destructive change, keep the old single goal
setup interface, and add multiple goals setup.  The single goal will
treated as one of the multiple goals, so old API users are not required to
make any change.

Link: https://lkml.kernel.org/r/20240219194431.159606-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 71 insertions, 7 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
index fe420967212159..b6cd99b64e8512 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -299,6 +299,41 @@ void damos_destroy_filter(struct damos_filter *f)
 	damos_free_filter(f);
 }
 
+struct damos_quota_goal *damos_new_quota_goal(
+		unsigned long (*get_score)(void *), void *get_score_arg)
+{
+	struct damos_quota_goal *goal;
+
+	goal = kmalloc(sizeof(*goal), GFP_KERNEL);
+	if (!goal)
+		return NULL;
+	goal->get_score = get_score;
+	goal->get_score_arg = get_score_arg;
+	INIT_LIST_HEAD(&goal->list);
+	return goal;
+}
+
+void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g)
+{
+	list_add_tail(&g->list, &q->goals);
+}
+
+static void damos_del_quota_goal(struct damos_quota_goal *g)
+{
+	list_del(&g->list);
+}
+
+static void damos_free_quota_goal(struct damos_quota_goal *g)
+{
+	kfree(g);
+}
+
+void damos_destroy_quota_goal(struct damos_quota_goal *g)
+{
+	damos_del_quota_goal(g);
+	damos_free_quota_goal(g);
+}
+
 /* initialize fields of @quota that normally API users wouldn't set */
 static struct damos_quota *damos_quota_init(struct damos_quota *quota)
 {
@@ -337,6 +372,8 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 	INIT_LIST_HEAD(&scheme->list);
 
 	scheme->quota = *(damos_quota_init(quota));
+	/* quota.goals should be separately set by caller */
+	INIT_LIST_HEAD(&scheme->quota.goals);
 
 	scheme->wmarks = *wmarks;
 	scheme->wmarks.activated = true;
@@ -373,8 +410,12 @@ static void damon_free_scheme(struct damos *s)
 
 void damon_destroy_scheme(struct damos *s)
 {
+	struct damos_quota_goal *g, *g_next;
 	struct damos_filter *f, *next;
 
+	damos_for_each_quota_goal_safe(g, g_next, &s->quota)
+		damos_destroy_quota_goal(g);
+
 	damos_for_each_filter_safe(f, next, s)
 		damos_destroy_filter(f);
 	damon_del_scheme(s);
@@ -1083,22 +1124,44 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
-/* Called only if quota->ms, quota->sz, or quota->goal.get_score are set */
+/* Return the highest score since it makes schemes least aggressive */
+static unsigned long damos_quota_score(struct damos_quota *quota)
+{
+	struct damos_quota_goal *goal;
+	unsigned long highest_score = 0;
+
+	if (quota->goal.get_score)
+		highest_score = quota->goal.get_score(
+				quota->goal.get_score_arg);
+
+	damos_for_each_quota_goal(goal, quota)
+		highest_score = max(highest_score,
+				goal->get_score(goal->get_score_arg));
+
+	return highest_score;
+}
+
+/*
+ * Called only if quota->ms, quota->sz, or quota->goal.get_score are set, or
+ * quota->goals is not empty
+ */
 static void damos_set_effective_quota(struct damos_quota *quota)
 {
 	unsigned long throughput;
 	unsigned long esz;
 
-	if (!quota->ms && !quota->goal.get_score) {
+	if (!quota->ms && !quota->goal.get_score &&
+			list_empty(&quota->goals)) {
 		quota->esz = quota->sz;
 		return;
 	}
 
-	if (quota->goal.get_score) {
+	if (quota->goal.get_score || !list_empty(&quota->goals)) {
+		unsigned long score = damos_quota_score(quota);
+
 		quota->esz_bp = damon_feed_loop_next_input(
 				max(quota->esz_bp, 10000UL),
-				quota->goal.get_score(
-					quota->goal.get_score_arg));
+				score);
 		esz = quota->esz_bp / 10000;
 	}
 
@@ -1108,7 +1171,7 @@ static void damos_set_effective_quota(struct damos_quota *quota)
 				quota->total_charged_ns;
 		else
 			throughput = PAGE_SIZE * 1024;
-		if (quota->goal.get_score)
+		if (quota->goal.get_score || !list_empty(&quota->goals))
 			esz = min(throughput * quota->ms, esz);
 		else
 			esz = throughput * quota->ms;
@@ -1128,7 +1191,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	unsigned long cumulated_sz;
 	unsigned int score, max_score = 0;
 
-	if (!quota->ms && !quota->sz && !quota->goal.get_score)
+	if (!quota->ms && !quota->sz && !quota->goal.get_score &&
+			list_empty(&quota->goals))
 		return;
 
 	/* New charge window starts */