[PATCH v3 18/28] slub: charge allocation to a memcg

[Glauber Costa]

This patch charges allocation of a slab object to a particular
memcg.

The cache is selected with mem_cgroup_get_kmem_cache(),
which is the biggest overhead we pay here, because
it happens at all allocations. However, other than forcing
a function call, this function is not very expensive, and
try to return as soon as we realize we are not a memcg cache.

The charge/uncharge functions are heavier, but are only called
for new page allocations.

The kmalloc_no_account variant is patched so the base
function is used and we don't even try to do cache
selection.

Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
---
 include/linux/slub_def.h |   39 ++++++++++++++++++---
 mm/slub.c                |   87 +++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 112 insertions(+), 14 deletions(-)

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index f822ca2..ba9c68b 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -13,6 +13,8 @@
 #include <linux/kobject.h>
 
 #include <linux/kmemleak.h>
+#include <linux/memcontrol.h>
+#include <linux/mm.h>
 
 enum stat_item {
 	ALLOC_FASTPATH,		/* Allocation from cpu slab */
@@ -228,27 +230,54 @@ static __always_inline int kmalloc_index(size_t size)
  * This ought to end up with a global pointer to the right cache
  * in kmalloc_caches.
  */
-static __always_inline struct kmem_cache *kmalloc_slab(size_t size)
+static __always_inline struct kmem_cache *kmalloc_slab(gfp_t flags, size_t size)
 {
+	struct kmem_cache *s;
 	int index = kmalloc_index(size);
 
 	if (index == 0)
 		return NULL;
 
-	return kmalloc_caches[index];
+	s = kmalloc_caches[index];
+
+	rcu_read_lock();
+	s = mem_cgroup_get_kmem_cache(s, flags);
+	rcu_read_unlock();
+
+	return s;
 }
 
 void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
 void *__kmalloc(size_t size, gfp_t flags);
 
 static __always_inline void *
-kmalloc_order(size_t size, gfp_t flags, unsigned int order)
+kmalloc_order_base(size_t size, gfp_t flags, unsigned int order)
 {
 	void *ret = (void *) __get_free_pages(flags | __GFP_COMP, order);
 	kmemleak_alloc(ret, size, 1, flags);
 	return ret;
 }
 
+static __always_inline void *
+kmalloc_order(size_t size, gfp_t flags, unsigned int order)
+{
+	void *ret = NULL;
+	struct page *page;
+
+	ret = kmalloc_order_base(size, flags, order);
+	if (!ret)
+		return ret;
+
+	page = virt_to_head_page(ret);
+
+	if (!mem_cgroup_new_kmem_page(page, flags)) {
+		put_page(page);
+		return NULL;
+	}
+
+	return ret;
+}
+
 /**
  * Calling this on allocated memory will check that the memory
  * is expected to be in use, and print warnings if not.
@@ -293,7 +322,7 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
 			return kmalloc_large(size, flags);
 
 		if (!(flags & SLUB_DMA)) {
-			struct kmem_cache *s = kmalloc_slab(size);
+			struct kmem_cache *s = kmalloc_slab(flags, size);
 
 			if (!s)
 				return ZERO_SIZE_PTR;
@@ -326,7 +355,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 {
 	if (__builtin_constant_p(size) &&
 		size <= SLUB_MAX_SIZE && !(flags & SLUB_DMA)) {
-			struct kmem_cache *s = kmalloc_slab(size);
+			struct kmem_cache *s = kmalloc_slab(flags, size);
 
 		if (!s)
 			return ZERO_SIZE_PTR;
diff --git a/mm/slub.c b/mm/slub.c
index 640872f..730e69f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1283,11 +1283,39 @@ static inline struct page *alloc_slab_page(gfp_t flags, int node,
 		return alloc_pages_exact_node(node, flags, order);
 }
 
+static inline unsigned long size_in_bytes(unsigned int order)
+{
+	return (1 << order) << PAGE_SHIFT;
+}
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+static void kmem_cache_inc_ref(struct kmem_cache *s)
+{
+	if (s->memcg_params.memcg)
+		atomic_inc(&s->memcg_params.refcnt);
+}
+static void kmem_cache_drop_ref(struct kmem_cache *s)
+{
+	if (s->memcg_params.memcg)
+		atomic_dec(&s->memcg_params.refcnt);
+}
+#else
+static inline void kmem_cache_inc_ref(struct kmem_cache *s)
+{
+}
+static inline void kmem_cache_drop_ref(struct kmem_cache *s)
+{
+}
+#endif
+
+
+
 static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 {
-	struct page *page;
+	struct page *page = NULL;
 	struct kmem_cache_order_objects oo = s->oo;
 	gfp_t alloc_gfp;
+	unsigned int memcg_allowed = oo_order(oo);
 
 	flags &= gfp_allowed_mask;
 
@@ -1296,13 +1324,29 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 	flags |= s->allocflags;
 
-	/*
-	 * Let the initial higher-order allocation fail under memory pressure
-	 * so we fall-back to the minimum order allocation.
-	 */
-	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
+	memcg_allowed = oo_order(oo);
+	if (!mem_cgroup_charge_slab(s, flags, size_in_bytes(memcg_allowed))) {
+
+		memcg_allowed = oo_order(s->min);
+		if (!mem_cgroup_charge_slab(s, flags,
+					    size_in_bytes(memcg_allowed))) {
+			if (flags & __GFP_WAIT)
+				local_irq_disable();
+			return NULL;
+		}
+	}
+
+	if (memcg_allowed == oo_order(oo)) {
+		/*
+		 * Let the initial higher-order allocation fail under memory
+		 * pressure so we fall-back to the minimum order allocation.
+		 */
+		alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) &
+			     ~__GFP_NOFAIL;
+
+		page = alloc_slab_page(alloc_gfp, node, oo);
+	}
 
-	page = alloc_slab_page(alloc_gfp, node, oo);
 	if (unlikely(!page)) {
 		oo = s->min;
 		/*
@@ -1313,13 +1357,25 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 		if (page)
 			stat(s, ORDER_FALLBACK);
+		/*
+		 * We reserved more than we used, time to give it back
+		 */
+		if (page && memcg_allowed != oo_order(oo)) {
+			unsigned long delta;
+			delta = memcg_allowed - oo_order(oo);
+			mem_cgroup_uncharge_slab(s, size_in_bytes(delta));
+		}
 	}
 
 	if (flags & __GFP_WAIT)
 		local_irq_disable();
 
-	if (!page)
+	if (!page) {
+		mem_cgroup_uncharge_slab(s, size_in_bytes(memcg_allowed));
 		return NULL;
+	}
+
+	kmem_cache_inc_ref(s);
 
 	if (kmemcheck_enabled
 		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
@@ -1419,6 +1475,9 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += pages;
 	__free_pages(page, order);
+
+	mem_cgroup_uncharge_slab(s, (1 << order) << PAGE_SHIFT);
+	kmem_cache_drop_ref(s);
 }
 
 #define need_reserve_slab_rcu						\
@@ -2310,6 +2369,9 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
 	if (slab_pre_alloc_hook(s, gfpflags))
 		return NULL;
 
+	rcu_read_lock();
+	s = mem_cgroup_get_kmem_cache(s, gfpflags);
+	rcu_read_unlock();
 redo:
 
 	/*
@@ -3372,9 +3434,15 @@ static void *kmalloc_large_node(size_t size, gfp_t flags, int node)
 
 	flags |= __GFP_COMP | __GFP_NOTRACK;
 	page = alloc_pages_node(node, flags, get_order(size));
-	if (page)
+	if (!page)
+		goto out;
+
+	if (!mem_cgroup_new_kmem_page(page, flags))
+		put_page(page);
+	else
 		ptr = page_address(page);
 
+out:
 	kmemleak_alloc(ptr, size, 1, flags);
 	return ptr;
 }
@@ -3476,6 +3544,7 @@ void kfree(const void *x)
 	if (unlikely(!PageSlab(page))) {
 		BUG_ON(!PageCompound(page));
 		kmemleak_free(x);
+		mem_cgroup_free_kmem_page(page);
 		put_page(page);
 		return;
 	}
-- 
1.7.7.6

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