[PATCH v4 1/3] mm/damon: Introduce DAMOS_QUOTA_HUGEPAGE auto tuning

[SJ Park <sj@kernel.org>]

From: Asier Gutierrez <gutierrez.asier@huawei-partners.com>

Introduce DAMOS_QUOTA_HUGEPAGE_MEM_BP auto tuning. Add a new DAMOS quota
goal metric to measure the amount of huge page consumption to total
memory consumption ratio.

Vmstat may lag, which in some cases may lead to NR_FREE_PAGES being
greater than or equal to the amount of RAM in the system. A guard is
added to avoid the extremely unlikely case [1]. In the case, return 100%
(10000 bp).

[1] https://lore.kernel.org/all/20260715151615.99767-1-sj@kernel.org/

Signed-off-by: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
 include/linux/damon.h |  2 ++
 mm/damon/core.c       | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 5607f98ec6306..310509455db13 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -153,6 +153,7 @@ enum damos_action {
  * @DAMOS_QUOTA_INACTIVE_MEM_BP:	Inactive to total LRU memory ratio.
  * @DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP:	Scheme-eligible memory ratio of a
  *					node in basis points (0-10000).
+ * @DAMOS_QUOTA_HUGEPAGE_MEM_BP:	Huge page to total used 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.
@@ -167,6 +168,7 @@ enum damos_quota_goal_metric {
 	DAMOS_QUOTA_ACTIVE_MEM_BP,
 	DAMOS_QUOTA_INACTIVE_MEM_BP,
 	DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP,
+	DAMOS_QUOTA_HUGEPAGE_MEM_BP,
 	NR_DAMOS_QUOTA_GOAL_METRICS,
 };
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index a5ea3e61e7f41..3fa1b096c8330 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -3038,6 +3038,22 @@ static unsigned int damos_get_in_active_mem_bp(bool active_ratio)
 	return mult_frac(inactive, 10000, total);
 }
 
+static unsigned int damos_hugepage_mem_bp(void)
+{
+	unsigned long thp, total_pages, free_pages;
+
+	total_pages = totalram_pages();
+	free_pages = global_zone_page_state(NR_FREE_PAGES);
+
+	if (total_pages <= free_pages)
+		return 10000;
+
+	thp = global_node_page_state(NR_ANON_THPS) +
+				global_node_page_state(NR_SHMEM_THPS) +
+				global_node_page_state(NR_FILE_THPS);
+	return mult_frac(thp, 10000, total_pages - free_pages);
+}
+
 static void damos_set_quota_goal_current_value(struct damon_ctx *c,
 		struct damos *s, struct damos_quota_goal *goal)
 {
@@ -3074,6 +3090,9 @@ static void damos_set_quota_goal_current_value(struct damon_ctx *c,
 		goal->current_value = damos_get_node_eligible_mem_bp(c, s,
 				goal->nid);
 		break;
+	case DAMOS_QUOTA_HUGEPAGE_MEM_BP:
+		goal->current_value = damos_hugepage_mem_bp();
+		break;
 	default:
 		break;
 	}
-- 
2.47.3