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.
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
include/linux/list_lru.h | 7 +--
mm/list_lru.c | 121 ++++++++++++++++++++++++++---------------------
mm/memcontrol.c | 6 ++-
3 files changed, 77 insertions(+), 57 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
diff --git a/mm/list_lru.c b/mm/list_lru.c
index d716edfaae38..4af820c191a7 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -59,8 +59,12 @@ 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;
}
@@ -187,7 +191,7 @@ 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))
@@ -216,8 +220,11 @@ __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;
@@ -261,6 +268,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
BUG();
}
}
+out:
return isolated;
}
@@ -353,20 +361,25 @@ 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)
@@ -380,14 +393,10 @@ 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;
@@ -421,13 +430,9 @@ 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);
@@ -435,20 +440,6 @@ 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;
@@ -459,15 +450,10 @@ 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,
@@ -484,6 +470,8 @@ 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);
@@ -493,7 +481,7 @@ 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);
}
@@ -504,15 +492,41 @@ 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);
}
@@ -527,7 +541,7 @@ 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;
@@ -582,11 +596,12 @@ 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 ec7a62f39326..94d8f742c32e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3643,6 +3643,10 @@ 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;
/*
@@ -3651,7 +3655,7 @@ 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);
}
--
2.11.0
