mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance

Introduce set_shrinker_bit() function to set shrinker-related bit in
memcg shrinker bitmap, and set the bit after the first item is added and
in case of reparenting destroyed memcg's items.

This will allow next patch to make shrinkers be called only, in case of
they have charged objects at the moment, and to improve shrink_slab()
performance.

[[email protected]: v9]
  Link: http://lkml.kernel.org/r/153112557572.4097.17315791419810749985.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/153063065671.1818.15914674956134687268.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
Tested-by: Shakeel Butt <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: Li RongQing <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Matthias Kaehlcke <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Philippe Ombredanne <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Sahitya Tummala <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Waiman Long <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/memcontrol.h

@@ -1286,6 +1286,8 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
 
 extern int memcg_expand_shrinker_maps(int new_id);
 
+extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
+				   int nid, int shrinker_id);
 #else
 #define for_each_memcg_cache_index(_idx)	\
 	for (; NULL; )
@@ -1308,6 +1310,8 @@ static inline void memcg_put_cache_ids(void)
 {
 }
 
+static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
+					  int nid, int shrinker_id) { }
 #endif /* CONFIG_MEMCG_KMEM */
 
 #endif /* _LINUX_MEMCONTROL_H */

mm/list_lru.c

@@ -30,6 +30,11 @@ static void list_lru_unregister(struct list_lru *lru)
 	mutex_unlock(&list_lrus_mutex);
 }
 
+static int lru_shrinker_id(struct list_lru *lru)
+{
+	return lru->shrinker_id;
+}
+
 static inline bool list_lru_memcg_aware(struct list_lru *lru)
 {
 	/*
@@ -93,6 +98,11 @@ static void list_lru_unregister(struct list_lru *lru)
 {
 }
 
+static int lru_shrinker_id(struct list_lru *lru)
+{
+	return -1;
+}
+
 static inline bool list_lru_memcg_aware(struct list_lru *lru)
 {
 	return false;
@@ -118,13 +128,17 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
 {
 	int nid = page_to_nid(virt_to_page(item));
 	struct list_lru_node *nlru = &lru->node[nid];
+	struct mem_cgroup *memcg;
 	struct list_lru_one *l;
 
 	spin_lock(&nlru->lock);
 	if (list_empty(item)) {
-		l = list_lru_from_kmem(nlru, item, NULL);
+		l = list_lru_from_kmem(nlru, item, &memcg);
 		list_add_tail(item, &l->list);
-		l->nr_items++;
+		/* Set shrinker bit if the first element was added */
+		if (!l->nr_items++)
+			memcg_set_shrinker_bit(memcg, nid,
+					       lru_shrinker_id(lru));
 		nlru->nr_items++;
 		spin_unlock(&nlru->lock);
 		return true;
@@ -507,6 +521,7 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
 	struct list_lru_node *nlru = &lru->node[nid];
 	int dst_idx = dst_memcg->kmemcg_id;
 	struct list_lru_one *src, *dst;
+	bool set;
 
 	/*
 	 * Since list_lru_{add,del} may be called under an IRQ-safe lock,
@@ -518,7 +533,10 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
 	dst = list_lru_from_memcg_idx(nlru, dst_idx);
 
 	list_splice_init(&src->list, &dst->list);
+	set = (!dst->nr_items && src->nr_items);
 	dst->nr_items += src->nr_items;
+	if (set)
+		memcg_set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
 	src->nr_items = 0;
 
 	spin_unlock_irq(&nlru->lock);

mm/memcontrol.c

@@ -422,6 +422,19 @@ unlock:
 	mutex_unlock(&memcg_shrinker_map_mutex);
 	return ret;
 }
+
+void memcg_set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
+{
+	if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
+		struct memcg_shrinker_map *map;
+
+		rcu_read_lock();
+		map = rcu_dereference(memcg->nodeinfo[nid]->shrinker_map);
+		set_bit(shrinker_id, map->map);
+		rcu_read_unlock();
+	}
+}
+
 #else /* CONFIG_MEMCG_KMEM */
 static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg)
 {