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Date: Tue, 12 Apr 2016 13:51:04 +0900
From: js1304@...il.com
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v2 09/11] mm/slab: separate cache_grow() to two parts
From: Joonsoo Kim <iamjoonsoo.kim@....com>
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 patch.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
mm/slab.c | 74 ++++++++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 52 insertions(+), 22 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index 1910589..2c28ad5 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -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))
@@ -1797,7 +1802,7 @@ 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))
continue;
@@ -2543,7 +2548,8 @@ 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;
@@ -2609,21 +2615,40 @@ static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid)
if (gfpflags_allow_blocking(local_flags))
local_irq_disable();
- check_irq_off();
- spin_lock(&n->list_lock);
- /* Make slab active. */
- list_add_tail(&page->lru, &(n->slabs_free));
- STATS_INC_GROWN(cachep);
- n->free_objects += cachep->num;
- spin_unlock(&n->list_lock);
- return page_node;
+ return page;
+
opps1:
kmem_freepages(cachep, page);
failed:
if (gfpflags_allow_blocking(local_flags))
local_irq_disable();
- return -1;
+ return NULL;
+}
+
+static void cache_grow_end(struct kmem_cache *cachep, struct page *page)
+{
+ struct kmem_cache_node *n;
+ void *list = NULL;
+
+ check_irq_off();
+
+ if (!page)
+ return;
+
+ INIT_LIST_HEAD(&page->lru);
+ n = get_node(cachep, page_to_nid(page));
+
+ spin_lock(&n->list_lock);
+ if (!page->active)
+ list_add_tail(&page->lru, &(n->slabs_free));
+ else
+ fixup_slab_list(cachep, n, page, &list);
+ STATS_INC_GROWN(cachep);
+ n->free_objects += cachep->num - page->active;
+ spin_unlock(&n->list_lock);
+
+ fixup_objfreelist_debug(cachep, &list);
}
#if DEBUG
@@ -2834,6 +2859,7 @@ static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
struct array_cache *ac;
int node;
void *list = NULL;
+ struct page *page;
check_irq_off();
node = numa_mem_id();
@@ -2861,7 +2887,6 @@ retry:
}
while (batchcount > 0) {
- struct page *page;
/* Get slab alloc is to come from. */
page = get_first_slab(n, false);
if (!page)
@@ -2894,8 +2919,6 @@ 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);
@@ -2904,14 +2927,18 @@ 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? */
@@ -3044,6 +3071,7 @@ 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;
@@ -3079,8 +3107,10 @@ 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);
@@ -3108,7 +3138,6 @@ 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);
@@ -3140,8 +3169,9 @@ retry:
must_grow:
spin_unlock(&n->list_lock);
- 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);
--
1.9.1
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