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authorMuchun Song <songmuchun@bytedance.com>2022-03-22 22:41:19 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 23:57:03 +0100
commit5abc1e37afa0335c52608d640fd30910b2eeda21 (patch)
treee87df05c9a087219e57e40bda5a614e7812d545c /mm
parentmm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online() (diff)
downloadlinux-5abc1e37afa0335c52608d640fd30910b2eeda21.tar.xz
linux-5abc1e37afa0335c52608d640fd30910b2eeda21.zip
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/20220228122126.37293-11-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>
Diffstat (limited to '')
-rw-r--r--mm/list_lru.c121
-rw-r--r--mm/memcontrol.c6
2 files changed, 73 insertions, 54 deletions
diff --git a/mm/list_lru.c b/mm/list_lru.c
index bffa80527723..fc938d8ff48f 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -60,8 +60,12 @@ list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
* from relocation (see memcg_update_list_lru).
*/
mlrus = rcu_dereference_check(lru->mlrus, lockdep_is_held(&nlru->lock));
- if (mlrus && idx >= 0)
- return &mlrus->mlru[idx]->node[nid];
+ if (mlrus && idx >= 0) {
+ struct list_lru_per_memcg *mlru;
+
+ mlru = rcu_dereference_check(mlrus->mlru[idx], true);
+ return mlru ? &mlru->node[nid] : NULL;
+ }
return &nlru->lru;
}
@@ -188,7 +192,7 @@ unsigned long list_lru_count_one(struct list_lru *lru,
rcu_read_lock();
l = list_lru_from_memcg_idx(lru, nid, memcg_cache_id(memcg));
- count = READ_ONCE(l->nr_items);
+ count = l ? READ_ONCE(l->nr_items) : 0;
rcu_read_unlock();
if (unlikely(count < 0))
@@ -217,8 +221,11 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
struct list_head *item, *n;
unsigned long isolated = 0;
- l = list_lru_from_memcg_idx(lru, nid, memcg_idx);
restart:
+ l = list_lru_from_memcg_idx(lru, nid, memcg_idx);
+ if (!l)
+ goto out;
+
list_for_each_safe(item, n, &l->list) {
enum lru_status ret;
@@ -262,6 +269,7 @@ restart:
BUG();
}
}
+out:
return isolated;
}
@@ -354,20 +362,25 @@ static struct list_lru_per_memcg *memcg_init_list_lru_one(gfp_t gfp)
return mlru;
}
-static int memcg_init_list_lru_range(struct list_lru_memcg *mlrus,
- int begin, int end)
+static void memcg_list_lru_free(struct list_lru *lru, int src_idx)
{
- int i;
+ struct list_lru_memcg *mlrus;
+ struct list_lru_per_memcg *mlru;
- for (i = begin; i < end; i++) {
- mlrus->mlru[i] = memcg_init_list_lru_one(GFP_KERNEL);
- if (!mlrus->mlru[i])
- goto fail;
- }
- return 0;
-fail:
- memcg_destroy_list_lru_range(mlrus, begin, i);
- return -ENOMEM;
+ spin_lock_irq(&lru->lock);
+ mlrus = rcu_dereference_protected(lru->mlrus, true);
+ mlru = rcu_dereference_protected(mlrus->mlru[src_idx], true);
+ rcu_assign_pointer(mlrus->mlru[src_idx], NULL);
+ spin_unlock_irq(&lru->lock);
+
+ /*
+ * The __list_lru_walk_one() can walk the list of this node.
+ * We need kvfree_rcu() here. And the walking of the list
+ * is under lru->node[nid]->lock, which can serve as a RCU
+ * read-side critical section.
+ */
+ if (mlru)
+ kvfree_rcu(mlru, rcu);
}
static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
@@ -381,14 +394,10 @@ static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
spin_lock_init(&lru->lock);
- mlrus = kvmalloc(struct_size(mlrus, mlru, size), GFP_KERNEL);
+ mlrus = kvzalloc(struct_size(mlrus, mlru, size), GFP_KERNEL);
if (!mlrus)
return -ENOMEM;
- if (memcg_init_list_lru_range(mlrus, 0, size)) {
- kvfree(mlrus);
- return -ENOMEM;
- }
RCU_INIT_POINTER(lru->mlrus, mlrus);
return 0;
@@ -422,13 +431,9 @@ static int memcg_update_list_lru(struct list_lru *lru, int old_size, int new_siz
if (!new)
return -ENOMEM;
- if (memcg_init_list_lru_range(new, old_size, new_size)) {
- kvfree(new);
- return -ENOMEM;
- }
-
spin_lock_irq(&lru->lock);
memcpy(&new->mlru, &old->mlru, flex_array_size(new, mlru, old_size));
+ memset(&new->mlru[old_size], 0, flex_array_size(new, mlru, new_size - old_size));
rcu_assign_pointer(lru->mlrus, new);
spin_unlock_irq(&lru->lock);
@@ -436,20 +441,6 @@ static int memcg_update_list_lru(struct list_lru *lru, int old_size, int new_siz
return 0;
}
-static void memcg_cancel_update_list_lru(struct list_lru *lru,
- int old_size, int new_size)
-{
- struct list_lru_memcg *mlrus;
-
- mlrus = rcu_dereference_protected(lru->mlrus,
- lockdep_is_held(&list_lrus_mutex));
- /*
- * Do not bother shrinking the array back to the old size, because we
- * cannot handle allocation failures here.
- */
- memcg_destroy_list_lru_range(mlrus, old_size, new_size);
-}
-
int memcg_update_all_list_lrus(int new_size)
{
int ret = 0;
@@ -460,15 +451,10 @@ int memcg_update_all_list_lrus(int new_size)
list_for_each_entry(lru, &memcg_list_lrus, list) {
ret = memcg_update_list_lru(lru, old_size, new_size);
if (ret)
- goto fail;
+ break;
}
-out:
mutex_unlock(&list_lrus_mutex);
return ret;
-fail:
- list_for_each_entry_continue_reverse(lru, &memcg_list_lrus, list)
- memcg_cancel_update_list_lru(lru, old_size, new_size);
- goto out;
}
static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
@@ -485,6 +471,8 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
spin_lock_irq(&nlru->lock);
src = list_lru_from_memcg_idx(lru, nid, src_idx);
+ if (!src)
+ goto out;
dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
list_splice_init(&src->list, &dst->list);
@@ -494,7 +482,7 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
src->nr_items = 0;
}
-
+out:
spin_unlock_irq(&nlru->lock);
}
@@ -505,15 +493,41 @@ static void memcg_drain_list_lru(struct list_lru *lru,
for_each_node(i)
memcg_drain_list_lru_node(lru, i, src_idx, dst_memcg);
+
+ memcg_list_lru_free(lru, src_idx);
}
-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)
{
+ struct cgroup_subsys_state *css;
struct list_lru *lru;
+ int src_idx = src->kmemcg_id;
+
+ /*
+ * Change kmemcg_id of this cgroup and all its descendants to the
+ * parent's id, and then move all entries from this cgroup's list_lrus
+ * to ones of the parent.
+ *
+ * After we have finished, all list_lrus corresponding to this cgroup
+ * are guaranteed to remain empty. So we can safely free this cgroup's
+ * list lrus in memcg_list_lru_free().
+ *
+ * Changing ->kmemcg_id to the parent can prevent memcg_list_lru_alloc()
+ * from allocating list lrus for this cgroup after memcg_list_lru_free()
+ * call.
+ */
+ rcu_read_lock();
+ css_for_each_descendant_pre(css, &src->css) {
+ struct mem_cgroup *memcg;
+
+ memcg = mem_cgroup_from_css(css);
+ memcg->kmemcg_id = dst->kmemcg_id;
+ }
+ rcu_read_unlock();
mutex_lock(&list_lrus_mutex);
list_for_each_entry(lru, &memcg_list_lrus, list)
- memcg_drain_list_lru(lru, src_idx, dst_memcg);
+ memcg_drain_list_lru(lru, src_idx, dst);
mutex_unlock(&list_lrus_mutex);
}
@@ -528,7 +542,7 @@ static bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
return true;
rcu_read_lock();
- allocated = !!rcu_dereference(lru->mlrus)->mlru[idx];
+ allocated = !!rcu_access_pointer(rcu_dereference(lru->mlrus)->mlru[idx]);
rcu_read_unlock();
return allocated;
@@ -576,11 +590,12 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
mlrus = rcu_dereference_protected(lru->mlrus, true);
while (i--) {
int index = table[i].memcg->kmemcg_id;
+ struct list_lru_per_memcg *mlru = table[i].mlru;
- if (mlrus->mlru[index])
- kfree(table[i].mlru);
+ if (index < 0 || rcu_dereference_protected(mlrus->mlru[index], true))
+ kfree(mlru);
else
- mlrus->mlru[index] = table[i].mlru;
+ rcu_assign_pointer(mlrus->mlru[index], mlru);
}
spin_unlock_irqrestore(&lru->lock, flags);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f08a0dc2ac36..69c09efc599d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3709,6 +3709,10 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
memcg_reparent_objcgs(memcg, parent);
+ /*
+ * memcg_drain_all_list_lrus() can change memcg->kmemcg_id.
+ * Cache it to local @kmemcg_id.
+ */
kmemcg_id = memcg->kmemcg_id;
/*
@@ -3717,7 +3721,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
* The ordering is imposed by list_lru_node->lock taken by
* memcg_drain_all_list_lrus().
*/
- memcg_drain_all_list_lrus(kmemcg_id, parent);
+ memcg_drain_all_list_lrus(memcg, parent);
memcg_free_cache_id(kmemcg_id);
}