mm: list_lru: replace linear array with xarray

If we run 10k containers in the system, the size of the
list_lru_memcg->lrus can be ~96KB per list_lru.  When we decrease the
number containers, the size of the array will not be shrinked.  It is
not scalable.  The xarray is a good choice for this case.  We can save a
lot of memory when there are tens of thousands continers in the system.
If we use xarray, we also can remove the logic code of resizing array,
which can simplify the code.

[akpm@linux-foundation.org: remove unused local]

Link: https://lkml.kernel.org/r/20220228122126.37293-13-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kari Argillander <kari.argillander@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 34 deletions

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 4b00fd8cb373..572c263561ac 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -11,6 +11,7 @@
 #include <linux/list.h>
 #include <linux/nodemask.h>
 #include <linux/shrinker.h>
+#include <linux/xarray.h>
 
 struct mem_cgroup;
 
@@ -37,12 +38,6 @@ struct list_lru_per_memcg {
 	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 __rcu	*mlru[];
-};
-
 struct list_lru_node {
 	/* protects all lists on the node, including per cgroup */
 	spinlock_t		lock;
@@ -57,10 +52,7 @@ struct list_lru {
 	struct list_head	list;
 	int			shrinker_id;
 	bool			memcg_aware;
-	/* protects ->mlrus->mlru[i] */
-	spinlock_t		lock;
-	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
-	struct list_lru_memcg	__rcu *mlrus;
+	struct xarray		xa;
 #endif
 };
 
@@ -77,7 +69,6 @@ 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_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent);
 
 /**
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b636732f0c14..066b7a3b8a9e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1685,18 +1685,6 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size);
 
 extern struct static_key_false memcg_kmem_enabled_key;
 
-extern int memcg_nr_cache_ids;
-void memcg_get_cache_ids(void);
-void memcg_put_cache_ids(void);
-
-/*
- * Helper macro to loop through all memcg-specific caches. Callers must still
- * check if the cache is valid (it is either valid or NULL).
- * the slab_mutex must be held when looping through those caches
- */
-#define for_each_memcg_cache_index(_idx)	\
-	for ((_idx) = 0; (_idx) < memcg_nr_cache_ids; (_idx)++)
-
 static inline bool memcg_kmem_enabled(void)
 {
 	return static_branch_likely(&memcg_kmem_enabled_key);
@@ -1753,9 +1741,6 @@ static inline void __memcg_kmem_uncharge_page(struct page *page, int order)
 {
 }
 
-#define for_each_memcg_cache_index(_idx)	\
-	for (; NULL; )
-
 static inline bool memcg_kmem_enabled(void)
 {
 	return false;
@@ -1766,14 +1751,6 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
 	return -1;
 }
 
-static inline void memcg_get_cache_ids(void)
-{
-}
-
-static inline void memcg_put_cache_ids(void)
-{
-}
-
 static inline struct mem_cgroup *mem_cgroup_from_obj(void *p)
 {
        return NULL;