mm/damon/core: implement PSI metric DAMOS quota goal

Extend DAMOS quota goal metric with system wide memory pressure stall
time.  Specifically, the system level 'some' PSI for memory is used.  The
target value can be set in microseconds.  DAMOS measures the increased
amount of the PSI metric in last quota_reset_interval and use the ratio of
it versus the user-specified target PSI value as the score for the
auto-tuning feedback loop.

Link: https://lkml.kernel.org/r/20240219194431.159606-14-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/damon.h

@@ -130,12 +130,14 @@ enum damos_action {
  * enum damos_quota_goal_metric - Represents the metric to be used as the goal
  *
  * @DAMOS_QUOTA_USER_INPUT:	User-input value.
+ * @DAMOS_QUOTA_SOME_MEM_PSI_US:	System level some memory PSI in us.
  * @NR_DAMOS_QUOTA_GOAL_METRICS:	Number of DAMOS quota goal metrics.
  *
  * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported.
  */
 enum damos_quota_goal_metric {
 	DAMOS_QUOTA_USER_INPUT,
+	DAMOS_QUOTA_SOME_MEM_PSI_US,
 	NR_DAMOS_QUOTA_GOAL_METRICS,
 };
 
@@ -144,6 +146,7 @@ enum damos_quota_goal_metric {
  * @metric:		Metric to be used for representing the goal.
  * @target_value:	Target value of @metric to achieve with the tuning.
  * @current_value:	Current value of @metric.
+ * @last_psi_total:	Last measured total PSI
  * @list:		List head for siblings.
  *
  * Data structure for getting the current score of the quota tuning goal.  The
@@ -159,6 +162,10 @@ struct damos_quota_goal {
 	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
+	/* metric-dependent fields */
+	union {
+		u64 last_psi_total;
+	};
 	struct list_head list;
 };
 

mm/damon/core.c

@@ -11,6 +11,7 @@
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/mm.h>
+#include <linux/psi.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 
@@ -1125,6 +1126,25 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	return min_input;
 }
 
+#ifdef CONFIG_PSI
+
+static u64 damos_get_some_mem_psi_total(void)
+{
+	if (static_branch_likely(&psi_disabled))
+		return 0;
+	return div_u64(psi_system.total[PSI_AVGS][PSI_MEM * 2],
+			NSEC_PER_USEC);
+}
+
+#else	/* CONFIG_PSI */
+
+static inline u64 damos_get_some_mem_psi_total(void)
+{
+	return 0;
+};
+
+#endif	/* CONFIG_PSI */
+
 static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 {
 	u64 now_psi_total;
@@ -1133,6 +1153,11 @@ static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
 	case DAMOS_QUOTA_USER_INPUT:
 		/* User should already set goal->current_value */
 		break;
+	case DAMOS_QUOTA_SOME_MEM_PSI_US:
+		now_psi_total = damos_get_some_mem_psi_total();
+		goal->current_value = now_psi_total - goal->last_psi_total;
+		goal->last_psi_total = now_psi_total;
+		break;
 	default:
 		break;
 	}