[PATCH 5/7] Fix not good check of mem_cgroup_local_usage()

[KAMEZAWA Hiroyuki]

Now, mem_cgroup_local_usage(memcg) is used as hint for scanning memory
cgroup hierarchy. If it returns true, the memcg has some reclaimable memory.

But this function doesn't take care of
  - unevictable pages
  - anon pages on swapless system.

This patch fixes the function to use LRU information.
For NUMA, for avoid scanning, numa scan bitmap is used. If it's
empty, some more precise check will be done.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |   43 +++++++++++++++++++++++++++++++++----------
 1 files changed, 33 insertions(+), 10 deletions(-)

Index: mmotm-0615/mm/memcontrol.c
===================================================================
--- mmotm-0615.orig/mm/memcontrol.c
+++ mmotm-0615/mm/memcontrol.c
@@ -632,15 +632,6 @@ static long mem_cgroup_read_stat(struct 
 	return val;
 }
 
-static long mem_cgroup_local_usage(struct mem_cgroup *mem)
-{
-	long ret;
-
-	ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
-	ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
-	return ret;
-}
-
 static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
 					 bool charge)
 {
@@ -1713,6 +1704,23 @@ static void mem_cgroup_numascan_init(str
 	mutex_init(&mem->numascan_mutex);
 }
 
+static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
+{
+	if (!nodes_empty(mem->scan_nodes))
+		return true;
+	/* slow path */
+	if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE))
+		return true;
+	if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE))
+		return true;
+	if (noswap || !total_swap_pages)
+		return false;
+	if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON))
+		return true;
+	if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON))
+		return true;
+	return false;
+}
 #else
 int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
 {
@@ -1722,6 +1730,21 @@ static void mem_cgroup_numascan_init(str
 {
 	return 0;
 }
+
+static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
+{
+	if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_FILE))
+		return true;
+	if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_FILE))
+		return true;
+	if (noswap || !total_swap_pages)
+		return false;
+	if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_ANON))
+		return true;
+	if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_ANON))
+		return true;
+	return false;
+}
 #endif
 
 
@@ -1811,7 +1834,7 @@ again:
 
 	while (visit--) {
 		victim = mem_cgroup_select_victim(root_mem);
-		if (!mem_cgroup_local_usage(victim)) {
+		if (!mem_cgroup_reclaimable(victim, noswap)) {
 			/* this cgroup's local usage == 0 */
 			css_put(&victim->css);
 			continue;

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