[RFC PATCH 01/11] mm/damon/core: introduce [in]active memory ratio damos quota goal metric

[SeongJae Park <sj@kernel.org>]

DAMOS_LRU_[DE]PRIO are DAMOS actions for making balance of active and
inactive memory size.  There is no appripriate 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 weill
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 517f48ffe782..c2fc6c8cbbe4 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -179,6 +179,8 @@ enum damos_action {
  * @DAMOS_QUOTA_SOME_MEM_PSI_US:	System level some memory PSI in us.
  * @DAMOS_QUOTA_NODE_MEM_USED_BP:	MemUsed ratio of a node.
  * @DAMOS_QUOTA_NODE_MEM_FREE_BP:	MemFree ratio of a node.
+ * @DAMOS_QUOTA_ACTIVE_MEM_BP:		Active to [in]active memory ratio.
+ * @DAMOS_QUOTA_INACTIVE_MEM_BP:	Inactive to [in]active 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.
@@ -188,6 +190,8 @@ enum damos_quota_goal_metric {
 	DAMOS_QUOTA_SOME_MEM_PSI_US,
 	DAMOS_QUOTA_NODE_MEM_USED_BP,
 	DAMOS_QUOTA_NODE_MEM_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 02493d71460c..88ffc826a118 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2027,6 +2027,23 @@ static __kernel_ulong_t damos_get_node_mem_bp(
 }
 #endif
 
+/*
+ * Returns LRU-active memory to LRU-inactive 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)
 {
@@ -2046,6 +2063,11 @@ static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 	case DAMOS_QUOTA_NODE_MEM_FREE_BP:
 		goal->current_value = damos_get_node_mem_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;
 	}
-- 
2.39.5