DAMOS_LRU_[DE]PRIO are DAMOS actions for making balance of active and
inactive memory size.  There is no appropriate DAMOS quota auto-tuning
target metric for the use case.  Add two new DAMOS quota goal metrics
for the purpose, namely DAMOS_QUOTA_[IN]ACTIVE_MEM_BP.  Those will
represent the ratio of [in]active memory to total (inactive + active)
memory.  Hence, users will be able to ask DAMON to, for example, "find
hot and cold memory, and move pages of those to active and inactive LRU
lists, adjusting the hot/cold thresholds aiming 50:50 active:inactive
memory ratio."

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h |  4 ++++
 mm/damon/core.c       | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 650e7ecfa32b..26fb8e90dff6 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -155,6 +155,8 @@ enum damos_action {
  * @DAMOS_QUOTA_NODE_MEM_FREE_BP:	MemFree ratio of a node.
  * @DAMOS_QUOTA_NODE_MEMCG_USED_BP:	MemUsed ratio of a node for a cgroup.
  * @DAMOS_QUOTA_NODE_MEMCG_FREE_BP:	MemFree ratio of a node for a cgroup.
+ * @DAMOS_QUOTA_ACTIVE_MEM_BP:		Active to total LRU memory ratio.
+ * @DAMOS_QUOTA_INACTIVE_MEM_BP:	Inactive to total LRU memory ratio.
  * @NR_DAMOS_QUOTA_GOAL_METRICS:	Number of DAMOS quota goal metrics.
  *
  * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported.
@@ -166,6 +168,8 @@ enum damos_quota_goal_metric {
 	DAMOS_QUOTA_NODE_MEM_FREE_BP,
 	DAMOS_QUOTA_NODE_MEMCG_USED_BP,
 	DAMOS_QUOTA_NODE_MEMCG_FREE_BP,
+	DAMOS_QUOTA_ACTIVE_MEM_BP,
+	DAMOS_QUOTA_INACTIVE_MEM_BP,
 	NR_DAMOS_QUOTA_GOAL_METRICS,
 };
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index abda850c28c0..d2ed75e521bd 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2132,6 +2132,23 @@ static unsigned long damos_get_node_memcg_used_bp(
 }
 #endif
 
+/*
+ * Returns LRU-active or inactive memory to total LRU memory size ratio.
+ */
+static unsigned int damos_get_in_active_mem_bp(bool active_ratio)
+{
+	unsigned long active, inactive, total;
+
+	/* This should align with /proc/meminfo output */
+	active = global_node_page_state(NR_LRU_BASE + LRU_ACTIVE_ANON) +
+		global_node_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);
+	inactive = global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_ANON) +
+		global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
+	total = active + inactive;
+	if (active_ratio)
+		return active * 10000 / total;
+	return inactive * 10000 / total;
+}
 
 static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 {
@@ -2154,6 +2171,11 @@ static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 	case DAMOS_QUOTA_NODE_MEMCG_FREE_BP:
 		goal->current_value = damos_get_node_memcg_used_bp(goal);
 		break;
+	case DAMOS_QUOTA_ACTIVE_MEM_BP:
+	case DAMOS_QUOTA_INACTIVE_MEM_BP:
+		goal->current_value = damos_get_in_active_mem_bp(
+				goal->metric == DAMOS_QUOTA_ACTIVE_MEM_BP);
+		break;
 	default:
 		break;
 	}
-- 
2.47.3