mm/damon: add node_eligible_mem_bp and node_ineligible_mem_bp goal metrics

This patch introduces two new DAMOS quota goal metrics for controlling memory distribution in heterogeneous memory systems (e.g., DRAM and CXL memory tiering) using physical address (PA) mode monitoring.

Changes since v4:
=================
https://lore.kernel.org/linux-mm/[email protected]/

- Fixed commit message description for DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP per review feedback
- Added clarifying comment for ops-common.h include (for damon_get_folio())
- Fixed build error when CONFIG_DAMON_PADDR is disabled by adding #ifdef CONFIG_DAMON_PADDR guards around functions using damon_get_folio()
- Dropped RFC tag per maintainer feedback

This patch is based on top of damon/next.

Background and Motivation
=========================

In heterogeneous memory systems, controlling memory distribution across NUMA nodes is essential for performance optimization. This patch enables system-wide page distribution with target-state goals such as "maintain 30% of scheme-eligible memory on CXL" using PA-mode DAMON schemes.

What These Metrics Measure
==========================

node_eligible_mem_bp:
scheme_eligible_bytes_on_node / total_scheme_eligible_bytes * 10000

node_ineligible_mem_bp:

    (total - scheme_eligible_bytes_on_node) / total * 10000

These metrics are complementary: eligible_bp + ineligible_bp = 10000 bp.

Two-Scheme Setup for Hot Page Distribution
==========================================

For maintaining hot memory on DRAM (node 0) and CXL (node 1) in a 7:3 ratio:

    PUSH scheme: migrate_hot from node 0 -> node 1
      goal: node_ineligible_mem_bp, nid=0, target=3000
      "Move hot pages from DRAM to CXL if more than 70% of hot data is
       in DRAM"

    PULL scheme: migrate_hot from node 1 -> node 0
      goal: node_eligible_mem_bp, nid=0, target=7000
      "Move hot pages from CXL to DRAM if less than 70% of hot data is
       in DRAM"

The complementary goals create a feedback loop that converges to the target distribution.

Testing Results
===============

Functionally tested on a two-node heterogeneous memory system with DRAM (node 0) and CXL memory (node 1). A PUSH+PULL scheme configuration using migrate_hot actions was used to reach a target hot memory ratio between the two tiers. Testing used the TEMPORAL goal tuner available in damon/next and mm-unstable.

With the TEMPORAL tuner, the system converges quickly to the target distribution. The tuner drives esz to maximum when under goal and to zero once the goal is met, forming a simple on/off feedback loop that stabilizes at the desired ratio.

With the CONSIST tuner, the scheme still converges but more slowly, as it migrates and then throttles itself based on quota feedback. The time to reach the goal varies depending on workload intensity.

Note: These metrics work with both TEMPORAL and CONSIST goal tuners.

Ravi Jonnalagadda (1):
mm/damon: add node_eligible_mem_bp and node_ineligible_mem_bp goal
metrics

 include/linux/damon.h    |   6 ++
 mm/damon/core.c          | 186 ++++++++++++++++++++++++++++++++++++---
 mm/damon/sysfs-schemes.c |  12 +++
 3 files changed, 190 insertions(+), 14 deletions(-)

base-commit: 97eefd14af390e1921f1fc5507140025095634e0

2.43.0

Add new quota goal metrics for memory tiering that track scheme-eligible memory distribution across NUMA nodes:

- DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP: ratio of eligible memory on a node
- DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP: ratio of ineligible memory on a node

These complementary metrics enable push-pull migration schemes that maintain a target memory distribution across different NUMA nodes representing different memory tiers, based on access patterns defined by each scheme.

The metrics iterate scheme-eligible regions and use damon_get_folio() to determine NUMA node placement of each folio, calculating the ratio of eligible memory on the specified node versus total eligible memory.

The implementation is guarded by CONFIG_DAMON_PADDR since damon_get_folio() is only available when physical address space monitoring is enabled.

---
 include/linux/damon.h    |   6 ++
 mm/damon/core.c          | 186 ++++++++++++++++++++++++++++++++++++---
 mm/damon/sysfs-schemes.c |  12 +++
 3 files changed, 190 insertions(+), 14 deletions(-)

index c15a7d2a05c6..98dbf6911dad 100644
@@ -193,6 +193,10 @@ enum damos_action {
  * @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.
+ * @DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP:	Scheme-eligible memory ratio of a
+ *					node.
+ * @DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP:	Scheme-ineligible memory ratio of a
+ *					node.
  * @NR_DAMOS_QUOTA_GOAL_METRICS:	Number of DAMOS quota goal metrics.
  *
  * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported.

@@ -206,6 +210,8 @@ enum damos_quota_goal_metric {
 	DAMOS_QUOTA_NODE_MEMCG_FREE_BP,
 	DAMOS_QUOTA_ACTIVE_MEM_BP,
 	DAMOS_QUOTA_INACTIVE_MEM_BP,
+	DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP,
+	DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP,
 	NR_DAMOS_QUOTA_GOAL_METRICS,
 };
 

index bf923709ab91..7e9cd19d5bff 100644
@@ -1084,6 +1084,14 @@ struct damos_sysfs_qgoal_metric_name damos_sysfs_qgoal_metric_names[] = {
 		.metric = DAMOS_QUOTA_INACTIVE_MEM_BP,
 		.name = "inactive_mem_bp",
 	},
+	{
+		.metric = DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP,
+		.name = "node_eligible_mem_bp",
+	},
+	{
+		.metric = DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP,
+		.name = "node_ineligible_mem_bp",
+	},
 };
 
 static ssize_t target_metric_show(struct kobject *kobj,

@@ -2717,6 +2725,10 @@ static int damos_sysfs_add_quota_score(
 		case DAMOS_QUOTA_NODE_MEM_FREE_BP:
 			goal->nid = sysfs_goal->nid;
 			break;
+		case DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP:
+		case DAMOS_QUOTA_NODE_INELIGIBLE_MEM_BP:
+			goal->nid = sysfs_goal->nid;
+			break;
 		case DAMOS_QUOTA_NODE_MEMCG_USED_BP:
 		case DAMOS_QUOTA_NODE_MEMCG_FREE_BP:
 			err = damon_sysfs_memcg_path_to_id(

2.43.0

I think you don't need to add the Reported-by: and Closes: for bug that found before this patch is merged. Could you please drop those?

[...]

The code changes look good to me. But, as I replied to the cover letter, I'd like to get sashiko review before giving my Reviewed-by:. Could you please rebase this to the latest mm-new and repost for getting the sashiko review?

Thanks,
SJ

Hello Ravi,

Thank you for revisioning while addressing my comments on the previous version!

Maybe because of this, sashiko was unable to review this.

To my understanding, there is no real reason to make this based on damon/next. And I'd like to get sashiko review for this patch. Could you please rebase this to latest mm-new and repost for that?

[...]

Other than the lack of the sashiko review, this cover letter looks good to me.

Thanks,
SJ

[...]