mm: list_lru: allocate list_lru_one only when needed

In our server, we found a suspected memory leak problem.  The kmalloc-32
consumes more than 6GB of memory.  Other kmem_caches consume less than
2GB memory.

After our in-depth analysis, the memory consumption of kmalloc-32 slab
cache is the cause of list_lru_one allocation.

  crash> p memcg_nr_cache_ids
  memcg_nr_cache_ids = $2 = 24574

memcg_nr_cache_ids is very large and memory consumption of each list_lru
can be calculated with the following formula.

  num_numa_node * memcg_nr_cache_ids * 32 (kmalloc-32)

There are 4 numa nodes in our system, so each list_lru consumes ~3MB.

  crash> list super_blocks | wc -l
  952

Every mount will register 2 list lrus, one is for inode, another is for
dentry.  There are 952 super_blocks.  So the total memory is 952 * 2 * 3
MB (~5.6GB).  But the number of memory cgroup is less than 500.  So I
guess more than 12286 containers have been deployed on this machine (I do
not know why there are so many containers, it may be a user's bug or the
user really want to do that).  And memcg_nr_cache_ids has not been reduced
to a suitable value.  This can waste a lot of memory.

Now the infrastructure for dynamic list_lru_one allocation is ready, so
remove statically allocated memory code to save memory.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muchun Song <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Anna Schumaker <[email protected]>
Cc: Chao Yu <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Fam Zheng <[email protected]>
Cc: Jaegeuk Kim <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Kari Argillander <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Qi Zheng <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Trond Myklebust <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: Xiongchun Duan <[email protected]>
Cc: Yang Shi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index ab912c49334f..c36db6dc2a65 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -32,14 +32,15 @@ struct list_lru_one {
 };
 
 struct list_lru_per_memcg {
+	struct rcu_head		rcu;
 	/* array of per cgroup per node lists, indexed by node id */
-	struct list_lru_one	node[0];
+	struct list_lru_one	node[];
 };
 
 struct list_lru_memcg {
 	struct rcu_head			rcu;
 	/* array of per cgroup lists, indexed by memcg_cache_id */
-	struct list_lru_per_memcg	*mlru[];
+	struct list_lru_per_memcg __rcu	*mlru[];
 };
 
 struct list_lru_node {
@@ -77,7 +78,7 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware,
 int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
 			 gfp_t gfp);
 int memcg_update_all_list_lrus(int num_memcgs);
-void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg);
+void memcg_drain_all_list_lrus(struct mem_cgroup *src, struct mem_cgroup *dst);
 
 /**
  * list_lru_add: add an element to the lru list's tail