[PATCH v6 24/31] list_lru: per-memcg walks

[Glauber Costa <glommer@openvz.org>]

This patch extend the list_lru interfaces to allow for a memcg
parameter. Because most of its users won't need it, instead of
modifying the function signatures we create a new set of _memcg()
functions and write the old API ontop of that.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/list_lru.h   |  26 ++++++++---
 include/linux/memcontrol.h |   2 +
 lib/list_lru.c             | 110 ++++++++++++++++++++++++++++++++++-----------
 3 files changed, 107 insertions(+), 31 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index f6756fb..9e6bbb1 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -99,23 +99,37 @@ static inline int list_lru_init_memcg(struct list_lru *lru)
 
 int list_lru_add(struct list_lru *lru, struct list_head *item);
 int list_lru_del(struct list_lru *lru, struct list_head *item);
-unsigned long
-list_lru_count_nodemask(struct list_lru *lru, nodemask_t *nodes_to_count);
+
+unsigned long list_lru_count_nodemask_memcg(struct list_lru *lru,
+			nodemask_t *nodes_to_count, struct mem_cgroup *memcg);
+
+static inline unsigned long
+list_lru_count_nodemask(struct list_lru *lru, nodemask_t *nodes_to_count)
+{
+	return list_lru_count_nodemask_memcg(lru, nodes_to_count, NULL);
+}
 
 static inline unsigned long list_lru_count(struct list_lru *lru)
 {
 	return list_lru_count_nodemask(lru, &lru->active_nodes);
 }
 
-
 typedef enum lru_status
 (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
 
 typedef void (*list_lru_dispose_cb)(struct list_head *dispose_list);
 
-unsigned long
-list_lru_walk_nodemask(struct list_lru *lru, list_lru_walk_cb isolate,
-	   void *cb_arg, unsigned long nr_to_walk, nodemask_t *nodes_to_walk);
+unsigned long list_lru_walk_nodemask_memcg(struct list_lru *lru,
+	list_lru_walk_cb isolate, void *cb_arg, unsigned long nr_to_walk,
+	nodemask_t *nodes_to_walk, struct mem_cgroup *memcg);
+
+static inline unsigned long list_lru_walk_nodemask(struct list_lru *lru,
+	list_lru_walk_cb isolate, void *cb_arg, unsigned long nr_to_walk,
+	nodemask_t *nodes_to_walk)
+{
+	return list_lru_walk_nodemask_memcg(lru, isolate, cb_arg, nr_to_walk,
+					    &lru->active_nodes, NULL);
+}
 
 static inline unsigned long
 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 50f199f..3eeece8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -593,6 +593,8 @@ static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
 #define for_each_memcg_cache_index(_idx)	\
 	for (; NULL; )
 
+#define memcg_limited_groups_array_size 0
+
 static inline bool memcg_kmem_enabled(void)
 {
 	return false;
diff --git a/lib/list_lru.c b/lib/list_lru.c
index a5753b2..f3a37f5 100644
--- a/lib/list_lru.c
+++ b/lib/list_lru.c
@@ -72,6 +72,23 @@ memcg_kmem_lru_of_page(struct list_lru *lru, struct page *page)
 	return lru_node_of_index(lru, memcg_id, nid);
 }
 
+/*
+ * This helper will loop through all node-data in the LRU, either global or
+ * per-memcg.  If memcg is either not present or not used,
+ * memcg_limited_groups_array_size will be 0. _idx starts at -1, and it will
+ * still be allowed to execute once.
+ *
+ * We convention that for _idx = -1, the global node info should be used.
+ * After that, we will go through each of the memcgs, starting at 0.
+ *
+ * We don't need any kind of locking for the loop because
+ * memcg_limited_groups_array_size can only grow, gaining new fields at the
+ * end. The old ones are just copied, and any interesting manipulation happen
+ * in the node list itself, and we already lock the list.
+ */
+#define for_each_memcg_lru_index(_idx)	\
+	for ((_idx) = -1; ((_idx) < memcg_limited_groups_array_size); (_idx)++)
+
 int
 list_lru_add(
 	struct list_lru	*lru,
@@ -131,13 +148,29 @@ list_lru_del(
 EXPORT_SYMBOL_GPL(list_lru_del);
 
 unsigned long
-list_lru_count_nodemask(struct list_lru *lru, nodemask_t *nodes_to_count)
+list_lru_count_nodemask_memcg(
+	struct list_lru *lru,
+	nodemask_t	*nodes_to_count,
+	struct mem_cgroup *memcg)
 {
 	long count = 0;
 	int nid;
+	nodemask_t nodes;
+	int memcg_id = -1;
+
+	if (memcg && memcg_kmem_is_active(memcg))
+		memcg_id = memcg_cache_id(memcg);
+	/*
+	 * Conservative code can call this setting nodes with node_setall.
+	 * This will generate an out of bound access for memcg.
+	 */
+	nodes_and(nodes, *nodes_to_count, node_online_map);
 
-	for_each_node_mask(nid, *nodes_to_count) {
-		struct list_lru_node *nlru = &lru->node[nid];
+	for_each_node_mask(nid, nodes) {
+		struct list_lru_node *nlru;
+		nlru = lru_node_of_index(lru, memcg_id, nid);
+		if (!nlru)
+			continue;
 
 		spin_lock(&nlru->lock);
 		BUG_ON(nlru->nr_items < 0);
@@ -147,17 +180,17 @@ list_lru_count_nodemask(struct list_lru *lru, nodemask_t *nodes_to_count)
 
 	return count;
 }
-EXPORT_SYMBOL_GPL(list_lru_count_nodemask);
+EXPORT_SYMBOL_GPL(list_lru_count_nodemask_memcg);
 
 static unsigned long
 list_lru_walk_node(
 	struct list_lru		*lru,
+	struct list_lru_node	*nlru,
 	int			nid,
 	list_lru_walk_cb	isolate,
 	void			*cb_arg,
 	unsigned long		*nr_to_walk)
 {
-	struct list_lru_node	*nlru = &lru->node[nid];
 	struct list_head *item, *n;
 	unsigned long isolated = 0;
 
@@ -197,25 +230,41 @@ restart:
 }
 
 unsigned long
-list_lru_walk_nodemask(
-	struct list_lru	*lru,
-	list_lru_walk_cb isolate,
-	void		*cb_arg,
-	unsigned long	nr_to_walk,
-	nodemask_t	*nodes_to_walk)
+list_lru_walk_nodemask_memcg(
+	struct list_lru		*lru,
+	list_lru_walk_cb	isolate,
+	void			*cb_arg,
+	unsigned long		nr_to_walk,
+	nodemask_t		*nodes_to_walk,
+	struct mem_cgroup	*memcg)
 {
 	long isolated = 0;
 	int nid;
+	nodemask_t nodes;
+	int memcg_id = -1;
+	struct list_lru_node *nlru;
 
-	for_each_node_mask(nid, *nodes_to_walk) {
-		isolated += list_lru_walk_node(lru, nid, isolate,
+	if (memcg && memcg_kmem_is_active(memcg))
+		memcg_id = memcg_cache_id(memcg);
+	/*
+	 * Conservative code can call this setting nodes with node_setall.
+	 * This will generate an out of bound access for memcg.
+	 */
+	nodes_and(nodes, *nodes_to_walk, node_online_map);
+
+	for_each_node_mask(nid, nodes) {
+		nlru = lru_node_of_index(lru, memcg_id, nid);
+		if (!nlru)
+			continue;
+
+		isolated += list_lru_walk_node(lru, nlru, nid, isolate,
 					       cb_arg, &nr_to_walk);
 		if (nr_to_walk <= 0)
 			break;
 	}
 	return isolated;
 }
-EXPORT_SYMBOL_GPL(list_lru_walk_nodemask);
+EXPORT_SYMBOL_GPL(list_lru_walk_nodemask_memcg);
 
 static unsigned long
 list_lru_dispose_all_node(
@@ -223,23 +272,34 @@ list_lru_dispose_all_node(
 	int			nid,
 	list_lru_dispose_cb	dispose)
 {
-	struct list_lru_node	*nlru = &lru->node[nid];
+	struct list_lru_node *nlru;
 	LIST_HEAD(dispose_list);
 	unsigned long disposed = 0;
+	int idx;
 
-	spin_lock(&nlru->lock);
-	while (!list_empty(&nlru->list)) {
-		list_splice_init(&nlru->list, &dispose_list);
-		disposed += nlru->nr_items;
-		nlru->nr_items = 0;
-		node_clear(nid, lru->active_nodes);
-		spin_unlock(&nlru->lock);
-
-		dispose(&dispose_list);
+	for_each_memcg_lru_index(idx) {
+		nlru = lru_node_of_index(lru, idx, nid);
+		if (!nlru)
+			continue;
 
 		spin_lock(&nlru->lock);
+		while (!list_empty(&nlru->list)) {
+			list_splice_init(&nlru->list, &dispose_list);
+
+			if (atomic_long_sub_and_test(nlru->nr_items,
+							&lru->node_totals[nid]))
+				node_clear(nid, lru->active_nodes);
+			disposed += nlru->nr_items;
+			nlru->nr_items = 0;
+			spin_unlock(&nlru->lock);
+
+			dispose(&dispose_list);
+
+			spin_lock(&nlru->lock);
+		}
+		spin_unlock(&nlru->lock);
 	}
-	spin_unlock(&nlru->lock);
+
 	return disposed;
 }
 
-- 
1.8.1.4