[RFC PATCH 1/3] mm/memory-tiers Add functions for tier memory usage in a cgroup

[Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>]

Add functions to provide tier based memory usage.  This is in preparation
for query via sysfs and for controlling a cgroup's top tier memory usage.

This patch introduces the tiered memory usage query interface and a
simple implementation.  A more efficient implementation to get toptier
memory usage will be introduced in the next patch.
---
 include/linux/memory-tiers.h |  2 ++
 mm/memcontrol.c              | 35 +++++++++++++++++++++++++++++++++++
 mm/memory-tiers.c            |  3 ++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index de4098f6d5d5..1177dcbbdeda 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -31,6 +31,8 @@ struct memory_tier {
 };
 
 extern bool numa_demotion_enabled;
+extern struct list_head memory_tiers;
+
 int node_create_and_set_memory_tier(int node, int tier);
 int next_demotion_node(int node);
 int node_set_memory_tier(int node, int tier);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index abec50f31fe6..2f6e95e6d200 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -63,6 +63,7 @@
 #include <linux/resume_user_mode.h>
 #include <linux/psi.h>
 #include <linux/seq_buf.h>
+#include <linux/memory-tiers.h>
 #include "internal.h"
 #include <net/sock.h>
 #include <net/ip.h>
@@ -3921,6 +3922,40 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
 
 	return 0;
 }
+
+unsigned long mem_cgroup_memtier_usage(struct mem_cgroup *memcg,
+					struct memory_tier *memtier)
+{
+	int node;
+	struct memory_tier *node_tier;
+	unsigned long usage = 0;
+
+	if (!memcg)
+		return 0;
+
+	rcu_read_lock();
+	for_each_online_node(node) {
+		node_tier = node_get_memory_tier(node);
+		if (node_tier == memtier)
+			usage += mem_cgroup_node_nr_lru_pages(memcg, node,
+					LRU_ALL, true);
+		node_put_memory_tier(node_tier);
+	}
+	rcu_read_unlock();
+	return usage;
+}
+
+unsigned long mem_cgroup_toptier_usage(struct mem_cgroup *memcg)
+{
+	struct memory_tier *top_tier;
+
+	top_tier = list_first_entry(&memory_tiers, struct memory_tier, list);
+	if (top_tier)
+		return mem_cgroup_memtier_usage(memcg, top_tier);
+	else
+		return 0;
+}
+
 #endif /* CONFIG_NUMA */
 
 static const unsigned int memcg1_stats[] = {
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 0dae3114e22c..d552ac1e9d57 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -16,7 +16,8 @@ struct demotion_nodes {
 #define to_memory_tier(device) container_of(device, struct memory_tier, dev)
 static void establish_migration_targets(void);
 static DEFINE_MUTEX(memory_tier_lock);
-static LIST_HEAD(memory_tiers);
+LIST_HEAD(memory_tiers);
+EXPORT_SYMBOL(memory_tiers);
 static int top_tier_rank;
 /*
  * node_demotion[] examples:
-- 
2.35.1