[PATCH] mm: use vmalloc fallback path for certain memcg allocations

[Anatoly Stepanov <astepanov@cloudlinux.com>]

As memcg array size can be up to:
sizeof(struct memcg_cache_array) + kmemcg_id * sizeof(void *);

where kmemcg_id can be up to MEMCG_CACHES_MAX_SIZE.

When a memcg instance count is large enough it can lead
to high order allocations up to order 7.

The same story with memcg_lrus allocations.
So let's work this around by utilizing vmalloc fallback path.

Signed-off-by: Anatoly Stepanov <astepanov@cloudlinux.com>
---
 include/linux/memcontrol.h | 16 ++++++++++++++++
 mm/list_lru.c              | 14 +++++++-------
 mm/slab_common.c           | 21 ++++++++++++++-------
 3 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 61d20c1..a281622 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -29,6 +29,9 @@
 #include <linux/mmzone.h>
 #include <linux/writeback.h>
 #include <linux/page-flags.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
 
 struct mem_cgroup;
 struct page;
@@ -878,4 +881,17 @@ static inline void memcg_kmem_update_page_stat(struct page *page,
 }
 #endif /* CONFIG_MEMCG && !CONFIG_SLOB */
 
+static inline void memcg_free(const void *ptr)
+{
+	is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);
+}
+
+static inline void *memcg_alloc(size_t size)
+{
+	if (likely(size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)))
+		return kzalloc(size, GFP_KERNEL|__GFP_NORETRY);
+
+	return vzalloc(size);
+}
+
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 234676e..8f49339 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -327,12 +327,12 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
 {
 	int size = memcg_nr_cache_ids;
 
-	nlru->memcg_lrus = kmalloc(size * sizeof(void *), GFP_KERNEL);
-	if (!nlru->memcg_lrus)
+	nlru->memcg_lrus = memcg_alloc(size * sizeof(void *));
+	if (nlru->memcg_lrus == NULL)
 		return -ENOMEM;
 
 	if (__memcg_init_list_lru_node(nlru->memcg_lrus, 0, size)) {
-		kfree(nlru->memcg_lrus);
+		memcg_free(nlru->memcg_lrus);
 		return -ENOMEM;
 	}
 
@@ -342,7 +342,7 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
 static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
 {
 	__memcg_destroy_list_lru_node(nlru->memcg_lrus, 0, memcg_nr_cache_ids);
-	kfree(nlru->memcg_lrus);
+	memcg_free(nlru->memcg_lrus);
 }
 
 static int memcg_update_list_lru_node(struct list_lru_node *nlru,
@@ -353,12 +353,12 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	BUG_ON(old_size > new_size);
 
 	old = nlru->memcg_lrus;
-	new = kmalloc(new_size * sizeof(void *), GFP_KERNEL);
+	new = memcg_alloc(new_size * sizeof(void *));
 	if (!new)
 		return -ENOMEM;
 
 	if (__memcg_init_list_lru_node(new, old_size, new_size)) {
-		kfree(new);
+		memcg_free(new);
 		return -ENOMEM;
 	}
 
@@ -375,7 +375,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	nlru->memcg_lrus = new;
 	spin_unlock_irq(&nlru->lock);
 
-	kfree(old);
+	memcg_free(old);
 	return 0;
 }
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 329b038..19f8cb5 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -157,9 +157,8 @@ static int init_memcg_params(struct kmem_cache *s,
 	if (!memcg_nr_cache_ids)
 		return 0;
 
-	arr = kzalloc(sizeof(struct memcg_cache_array) +
-		      memcg_nr_cache_ids * sizeof(void *),
-		      GFP_KERNEL);
+	arr = memcg_alloc(sizeof(struct memcg_cache_array) +
+			memcg_nr_cache_ids * sizeof(void *));
 	if (!arr)
 		return -ENOMEM;
 
@@ -170,7 +169,15 @@ static int init_memcg_params(struct kmem_cache *s,
 static void destroy_memcg_params(struct kmem_cache *s)
 {
 	if (is_root_cache(s))
-		kfree(rcu_access_pointer(s->memcg_params.memcg_caches));
+		memcg_free(rcu_access_pointer(s->memcg_params.memcg_caches));
+}
+
+static void memcg_rcu_free(struct rcu_head *rcu)
+{
+	struct memcg_cache_array *arr;
+
+	arr = container_of(rcu, struct memcg_cache_array, rcu);
+	memcg_free(arr);
 }
 
 static int update_memcg_params(struct kmem_cache *s, int new_array_size)
@@ -180,8 +187,8 @@ static int update_memcg_params(struct kmem_cache *s, int new_array_size)
 	if (!is_root_cache(s))
 		return 0;
 
-	new = kzalloc(sizeof(struct memcg_cache_array) +
-		      new_array_size * sizeof(void *), GFP_KERNEL);
+	new = memcg_alloc(sizeof(struct memcg_cache_array) +
+				new_array_size * sizeof(void *));
 	if (!new)
 		return -ENOMEM;
 
@@ -193,7 +200,7 @@ static int update_memcg_params(struct kmem_cache *s, int new_array_size)
 
 	rcu_assign_pointer(s->memcg_params.memcg_caches, new);
 	if (old)
-		kfree_rcu(old, rcu);
+		call_rcu(&old->rcu, memcg_rcu_free);
 	return 0;
 }
 
-- 
1.8.3.1

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