Commit 76b342bd authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
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mm/slab: separate cache_grow() to two parts

This is a preparation step to implement lockless allocation path when
there is no free objects in kmem_cache.

What we'd like to do here is to refill cpu cache without holding a node
lock.  To accomplish this purpose, refill should be done after new slab
allocation but before attaching the slab to the management list.  So,
this patch separates cache_grow() to two parts, allocation and attaching
to the list in order to add some code inbetween them in the following

Signed-off-by: default avatarJoonsoo Kim <>
Cc: Jesper Dangaard Brouer <>
Cc: Christoph Lameter <>
Cc: Pekka Enberg <>
Cc: David Rientjes <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 511e3a05
......@@ -213,6 +213,11 @@ static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list);
static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp);
static void cache_reap(struct work_struct *unused);
static inline void fixup_objfreelist_debug(struct kmem_cache *cachep,
void **list);
static inline void fixup_slab_list(struct kmem_cache *cachep,
struct kmem_cache_node *n, struct page *page,
void **list);
static int slab_early_init = 1;
#define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))
......@@ -1810,7 +1815,7 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
* Needed to avoid possible looping condition
* in cache_grow()
* in cache_grow_begin()
if (OFF_SLAB(freelist_cache))
......@@ -2556,7 +2561,8 @@ static void slab_map_pages(struct kmem_cache *cache, struct page *page,
* Grow (by 1) the number of slabs within a cache. This is called by
* kmem_cache_alloc() when there are no active objs left in a cache.
static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid)
static struct page *cache_grow_begin(struct kmem_cache *cachep,
gfp_t flags, int nodeid)
void *freelist;
size_t offset;
......@@ -2622,21 +2628,40 @@ static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid)
if (gfpflags_allow_blocking(local_flags))
/* Make slab active. */
list_add_tail(&page->lru, &(n->slabs_free));
n->free_objects += cachep->num;
return page_node;
return page;
kmem_freepages(cachep, page);
if (gfpflags_allow_blocking(local_flags))
return -1;
return NULL;
static void cache_grow_end(struct kmem_cache *cachep, struct page *page)
struct kmem_cache_node *n;
void *list = NULL;
if (!page)
n = get_node(cachep, page_to_nid(page));
if (!page->active)
list_add_tail(&page->lru, &(n->slabs_free));
fixup_slab_list(cachep, n, page, &list);
n->free_objects += cachep->num - page->active;
fixup_objfreelist_debug(cachep, &list);
......@@ -2847,6 +2872,7 @@ static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
struct array_cache *ac;
int node;
void *list = NULL;
struct page *page;
node = numa_mem_id();
......@@ -2874,7 +2900,6 @@ retry:
while (batchcount > 0) {
struct page *page;
/* Get slab alloc is to come from. */
page = get_first_slab(n, false);
if (!page)
......@@ -2907,8 +2932,6 @@ alloc_done:
fixup_objfreelist_debug(cachep, &list);
if (unlikely(!ac->avail)) {
int x;
/* Check if we can use obj in pfmemalloc slab */
if (sk_memalloc_socks()) {
void *obj = cache_alloc_pfmemalloc(cachep, n, flags);
......@@ -2917,14 +2940,18 @@ alloc_done:
return obj;
x = cache_grow(cachep, gfp_exact_node(flags), node);
page = cache_grow_begin(cachep, gfp_exact_node(flags), node);
cache_grow_end(cachep, page);
/* cache_grow can reenable interrupts, then ac could change. */
* cache_grow_begin() can reenable interrupts,
* then ac could change.
ac = cpu_cache_get(cachep);
node = numa_mem_id();
/* no objects in sight? abort */
if (x < 0 && ac->avail == 0)
if (!page && ac->avail == 0)
return NULL;
if (!ac->avail) /* objects refilled by interrupt? */
......@@ -3057,6 +3084,7 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
struct zone *zone;
enum zone_type high_zoneidx = gfp_zone(flags);
void *obj = NULL;
struct page *page;
int nid;
unsigned int cpuset_mems_cookie;
......@@ -3092,8 +3120,10 @@ retry:
* We may trigger various forms of reclaim on the allowed
* set and go into memory reserves if necessary.
nid = cache_grow(cache, flags, numa_mem_id());
if (nid >= 0) {
page = cache_grow_begin(cache, flags, numa_mem_id());
cache_grow_end(cache, page);
if (page) {
nid = page_to_nid(page);
obj = ____cache_alloc_node(cache,
gfp_exact_node(flags), nid);
......@@ -3121,7 +3151,6 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
struct kmem_cache_node *n;
void *obj;
void *list = NULL;
int x;
VM_BUG_ON(nodeid < 0 || nodeid >= MAX_NUMNODES);
n = get_node(cachep, nodeid);
......@@ -3153,8 +3182,9 @@ retry:
x = cache_grow(cachep, gfp_exact_node(flags), nodeid);
if (x >= 0)
page = cache_grow_begin(cachep, gfp_exact_node(flags), nodeid);
cache_grow_end(cachep, page);
if (page)
goto retry;
return fallback_alloc(cachep, flags);
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