[PATCH 3/3] mm/damon/sysfs-schemes: expose NODE_TARGET_MEM_BP metric

[Ravi Jonnalagadda <ravis.opensrc@gmail.com>]

Add sysfs support for the new NODE_TARGET_MEM_BP quota goal metric.
This exposes the metric as 'node_target_mem_bp' under the quota goal's
target_metric attribute.

The metric measures the ratio of scheme-eligible memory (regions matching
the scheme's access pattern) on a specified NUMA node to the node's total
capacity, expressed in basis points (bp, 1/10000).

Users can configure this metric by:
1. Setting target_metric to 'node_target_mem_bp'
2. Setting nid to the target NUMA node
3. Setting target_value to the desired ratio in basis points

The current_value attribute shows the measured ratio, which can be used
by userspace to compute the actual bytes of scheme-eligible memory on
the node: bytes = current_value * node_capacity / 10000.

This is particularly useful for tiered memory systems to monitor and
control the distribution of hot pages across NUMA nodes.

Suggested-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Ravi Jonnalagadda <ravis.opensrc@gmail.com>
---
 mm/damon/sysfs-schemes.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 3a699dcd5a7f..50133263c592 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1038,6 +1038,10 @@ struct damos_sysfs_qgoal_metric_name damos_sysfs_qgoal_metric_names[] = {
 		.metric = DAMOS_QUOTA_NODE_MEMCG_FREE_BP,
 		.name = "node_memcg_free_bp",
 	},
+	{
+		.metric = DAMOS_QUOTA_NODE_TARGET_MEM_BP,
+		.name = "node_target_mem_bp",
+	},
 };
 
 static ssize_t target_metric_show(struct kobject *kobj,
@@ -2554,6 +2558,7 @@ static int damos_sysfs_add_quota_score(
 			break;
 		case DAMOS_QUOTA_NODE_MEM_USED_BP:
 		case DAMOS_QUOTA_NODE_MEM_FREE_BP:
+		case DAMOS_QUOTA_NODE_TARGET_MEM_BP:
 			goal->nid = sysfs_goal->nid;
 			break;
 		case DAMOS_QUOTA_NODE_MEMCG_USED_BP:
-- 
2.43.0