Merge branch 'slab/next' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux

Pull slab changes from Pekka Enberg:
 "The biggest change is byte-sized freelist indices which reduces slab
  freelist memory usage:

    https://lkml.org/lkml/2013/12/2/64"

* 'slab/next' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux:
  mm: slab/slub: use page->list consistently instead of page->lru
  mm/slab.c: cleanup outdated comments and unify variables naming
  slab: fix wrongly used macro
  slub: fix high order page allocation problem with __GFP_NOFAIL
  slab: Make allocations with GFP_ZERO slightly more efficient
  slab: make more slab management structure off the slab
  slab: introduce byte sized index for the freelist of a slab
  slab: restrict the number of objects in a slab
  slab: introduce helper functions to get/set free object
  slab: factor out calculate nr objects in cache_estimate

1 files changed, 107 insertions, 76 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 3db4cb06e32..388cb1ae6fb 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -157,6 +157,17 @@
 #define ARCH_KMALLOC_FLAGS SLAB_HWCACHE_ALIGN
 #endif
 
+#define FREELIST_BYTE_INDEX (((PAGE_SIZE >> BITS_PER_BYTE) \
+				<= SLAB_OBJ_MIN_SIZE) ? 1 : 0)
+
+#if FREELIST_BYTE_INDEX
+typedef unsigned char freelist_idx_t;
+#else
+typedef unsigned short freelist_idx_t;
+#endif
+
+#define SLAB_OBJ_MAX_NUM (1 << sizeof(freelist_idx_t) * BITS_PER_BYTE)
+
 /*
  * true if a page was allocated from pfmemalloc reserves for network-based
  * swap
@@ -277,8 +288,8 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent)
  * OTOH the cpuarrays can contain lots of objects,
  * which could lock up otherwise freeable slabs.
  */
-#define REAPTIMEOUT_CPUC	(2*HZ)
-#define REAPTIMEOUT_LIST3	(4*HZ)
+#define REAPTIMEOUT_AC		(2*HZ)
+#define REAPTIMEOUT_NODE	(4*HZ)
 
 #if STATS
 #define	STATS_INC_ACTIVE(x)	((x)->num_active++)
@@ -565,9 +576,31 @@ static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
 	return cachep->array[smp_processor_id()];
 }
 
-static size_t slab_mgmt_size(size_t nr_objs, size_t align)
+static int calculate_nr_objs(size_t slab_size, size_t buffer_size,
+				size_t idx_size, size_t align)
 {
-	return ALIGN(nr_objs * sizeof(unsigned int), align);
+	int nr_objs;
+	size_t freelist_size;
+
+	/*
+	 * Ignore padding for the initial guess. The padding
+	 * is at most @align-1 bytes, and @buffer_size is at
+	 * least @align. In the worst case, this result will
+	 * be one greater than the number of objects that fit
+	 * into the memory allocation when taking the padding
+	 * into account.
+	 */
+	nr_objs = slab_size / (buffer_size + idx_size);
+
+	/*
+	 * This calculated number will be either the right
+	 * amount, or one greater than what we want.
+	 */
+	freelist_size = slab_size - nr_objs * buffer_size;
+	if (freelist_size < ALIGN(nr_objs * idx_size, align))
+		nr_objs--;
+
+	return nr_objs;
 }
 
 /*
@@ -600,25 +633,9 @@ static void cache_estimate(unsigned long gfporder, size_t buffer_size,
 		nr_objs = slab_size / buffer_size;
 
 	} else {
-		/*
-		 * Ignore padding for the initial guess. The padding
-		 * is at most @align-1 bytes, and @buffer_size is at
-		 * least @align. In the worst case, this result will
-		 * be one greater than the number of objects that fit
-		 * into the memory allocation when taking the padding
-		 * into account.
-		 */
-		nr_objs = (slab_size) / (buffer_size + sizeof(unsigned int));
-
-		/*
-		 * This calculated number will be either the right
-		 * amount, or one greater than what we want.
-		 */
-		if (slab_mgmt_size(nr_objs, align) + nr_objs*buffer_size
-		       > slab_size)
-			nr_objs--;
-
-		mgmt_size = slab_mgmt_size(nr_objs, align);
+		nr_objs = calculate_nr_objs(slab_size, buffer_size,
+					sizeof(freelist_idx_t), align);
+		mgmt_size = ALIGN(nr_objs * sizeof(freelist_idx_t), align);
 	}
 	*num = nr_objs;
 	*left_over = slab_size - nr_objs*buffer_size - mgmt_size;
@@ -1067,7 +1084,7 @@ static int init_cache_node_node(int node)
 
 	list_for_each_entry(cachep, &slab_caches, list) {
 		/*
-		 * Set up the size64 kmemlist for cpu before we can
+		 * Set up the kmem_cache_node for cpu before we can
 		 * begin anything. Make sure some other cpu on this
 		 * node has not already allocated this
 		 */
@@ -1076,12 +1093,12 @@ static int init_cache_node_node(int node)
 			if (!n)
 				return -ENOMEM;
 			kmem_cache_node_init(n);
-			n->next_reap = jiffies + REAPTIMEOUT_LIST3 +
-			    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+			n->next_reap = jiffies + REAPTIMEOUT_NODE +
+			    ((unsigned long)cachep) % REAPTIMEOUT_NODE;
 
 			/*
-			 * The l3s don't come and go as CPUs come and
-			 * go.  slab_mutex is sufficient
+			 * The kmem_cache_nodes don't come and go as CPUs
+			 * come and go.  slab_mutex is sufficient
 			 * protection here.
 			 */
 			cachep->node[node] = n;
@@ -1406,8 +1423,8 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
 	for_each_online_node(node) {
 		cachep->node[node] = &init_kmem_cache_node[index + node];
 		cachep->node[node]->next_reap = jiffies +
-		    REAPTIMEOUT_LIST3 +
-		    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+		    REAPTIMEOUT_NODE +
+		    ((unsigned long)cachep) % REAPTIMEOUT_NODE;
 	}
 }
 
@@ -2010,6 +2027,10 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
 		if (!num)
 			continue;
 
+		/* Can't handle number of objects more than SLAB_OBJ_MAX_NUM */
+		if (num > SLAB_OBJ_MAX_NUM)
+			break;
+
 		if (flags & CFLGS_OFF_SLAB) {
 			/*
 			 * Max number of objs-per-slab for caches which
@@ -2017,7 +2038,7 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
 			 * looping condition in cache_grow().
 			 */
 			offslab_limit = size;
-			offslab_limit /= sizeof(unsigned int);
+			offslab_limit /= sizeof(freelist_idx_t);
 
  			if (num > offslab_limit)
 				break;
@@ -2103,8 +2124,8 @@ static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
 		}
 	}
 	cachep->node[numa_mem_id()]->next_reap =
-			jiffies + REAPTIMEOUT_LIST3 +
-			((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+			jiffies + REAPTIMEOUT_NODE +
+			((unsigned long)cachep) % REAPTIMEOUT_NODE;
 
 	cpu_cache_get(cachep)->avail = 0;
 	cpu_cache_get(cachep)->limit = BOOT_CPUCACHE_ENTRIES;
@@ -2243,7 +2264,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	 * it too early on. Always use on-slab management when
 	 * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
 	 */
-	if ((size >= (PAGE_SIZE >> 3)) && !slab_early_init &&
+	if ((size >= (PAGE_SIZE >> 5)) && !slab_early_init &&
 	    !(flags & SLAB_NOLEAKTRACE))
 		/*
 		 * Size is large, assume best to place the slab management obj
@@ -2252,6 +2273,12 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 		flags |= CFLGS_OFF_SLAB;
 
 	size = ALIGN(size, cachep->align);
+	/*
+	 * We should restrict the number of objects in a slab to implement
+	 * byte sized index. Refer comment on SLAB_OBJ_MIN_SIZE definition.
+	 */
+	if (FREELIST_BYTE_INDEX && size < SLAB_OBJ_MIN_SIZE)
+		size = ALIGN(SLAB_OBJ_MIN_SIZE, cachep->align);
 
 	left_over = calculate_slab_order(cachep, size, cachep->align, flags);
 
@@ -2259,7 +2286,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 		return -E2BIG;
 
 	freelist_size =
-		ALIGN(cachep->num * sizeof(unsigned int), cachep->align);
+		ALIGN(cachep->num * sizeof(freelist_idx_t), cachep->align);
 
 	/*
 	 * If the slab has been placed off-slab, and we have enough space then
@@ -2272,7 +2299,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 
 	if (flags & CFLGS_OFF_SLAB) {
 		/* really off slab. No need for manual alignment */
-		freelist_size = cachep->num * sizeof(unsigned int);
+		freelist_size = cachep->num * sizeof(freelist_idx_t);
 
 #ifdef CONFIG_PAGE_POISONING
 		/* If we're going to use the generic kernel_map_pages()
@@ -2300,10 +2327,10 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	if (flags & CFLGS_OFF_SLAB) {
 		cachep->freelist_cache = kmalloc_slab(freelist_size, 0u);
 		/*
-		 * This is a possibility for one of the malloc_sizes caches.
+		 * This is a possibility for one of the kmalloc_{dma,}_caches.
 		 * But since we go off slab only for object size greater than
-		 * PAGE_SIZE/8, and malloc_sizes gets created in ascending order,
-		 * this should not happen at all.
+		 * PAGE_SIZE/8, and kmalloc_{dma,}_caches get created
+		 * in ascending order,this should not happen at all.
 		 * But leave a BUG_ON for some lucky dude.
 		 */
 		BUG_ON(ZERO_OR_NULL_PTR(cachep->freelist_cache));
@@ -2511,14 +2538,17 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
 
 /*
  * Get the memory for a slab management obj.
- * For a slab cache when the slab descriptor is off-slab, slab descriptors
- * always come from malloc_sizes caches.  The slab descriptor cannot
- * come from the same cache which is getting created because,
- * when we are searching for an appropriate cache for these
- * descriptors in kmem_cache_create, we search through the malloc_sizes array.
- * If we are creating a malloc_sizes cache here it would not be visible to
- * kmem_find_general_cachep till the initialization is complete.
- * Hence we cannot have freelist_cache same as the original cache.
+ *
+ * For a slab cache when the slab descriptor is off-slab, the
+ * slab descriptor can't come from the same cache which is being created,
+ * Because if it is the case, that means we defer the creation of
+ * the kmalloc_{dma,}_cache of size sizeof(slab descriptor) to this point.
+ * And we eventually call down to __kmem_cache_create(), which
+ * in turn looks up in the kmalloc_{dma,}_caches for the disired-size one.
+ * This is a "chicken-and-egg" problem.
+ *
+ * So the off-slab slab descriptor shall come from the kmalloc_{dma,}_caches,
+ * which are all initialized during kmem_cache_init().
  */
 static void *alloc_slabmgmt(struct kmem_cache *cachep,
 				   struct page *page, int colour_off,
@@ -2542,9 +2572,15 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep,
 	return freelist;
 }
 
-static inline unsigned int *slab_freelist(struct page *page)
+static inline freelist_idx_t get_free_obj(struct page *page, unsigned char idx)
 {
-	return (unsigned int *)(page->freelist);
+	return ((freelist_idx_t *)page->freelist)[idx];
+}
+
+static inline void set_free_obj(struct page *page,
+					unsigned char idx, freelist_idx_t val)
+{
+	((freelist_idx_t *)(page->freelist))[idx] = val;
 }
 
 static void cache_init_objs(struct kmem_cache *cachep,
@@ -2589,7 +2625,7 @@ static void cache_init_objs(struct kmem_cache *cachep,
 		if (cachep->ctor)
 			cachep->ctor(objp);
 #endif
-		slab_freelist(page)[i] = i;
+		set_free_obj(page, i, i);
 	}
 }
 
@@ -2608,7 +2644,7 @@ static void *slab_get_obj(struct kmem_cache *cachep, struct page *page,
 {
 	void *objp;
 
-	objp = index_to_obj(cachep, page, slab_freelist(page)[page->active]);
+	objp = index_to_obj(cachep, page, get_free_obj(page, page->active));
 	page->active++;
 #if DEBUG
 	WARN_ON(page_to_nid(virt_to_page(objp)) != nodeid);
@@ -2629,7 +2665,7 @@ static void slab_put_obj(struct kmem_cache *cachep, struct page *page,
 
 	/* Verify double free bug */
 	for (i = page->active; i < cachep->num; i++) {
-		if (slab_freelist(page)[i] == objnr) {
+		if (get_free_obj(page, i) == objnr) {
 			printk(KERN_ERR "slab: double free detected in cache "
 					"'%s', objp %p\n", cachep->name, objp);
 			BUG();
@@ -2637,7 +2673,7 @@ static void slab_put_obj(struct kmem_cache *cachep, struct page *page,
 	}
 #endif
 	page->active--;
-	slab_freelist(page)[page->active] = objnr;
+	set_free_obj(page, page->active, objnr);
 }
 
 /*
@@ -2886,9 +2922,9 @@ retry:
 		/* move slabp to correct slabp list: */
 		list_del(&page->lru);
 		if (page->active == cachep->num)
-			list_add(&page->list, &n->slabs_full);
+			list_add(&page->lru, &n->slabs_full);
 		else
-			list_add(&page->list, &n->slabs_partial);
+			list_add(&page->lru, &n->slabs_partial);
 	}
 
 must_grow:
@@ -3245,11 +3281,11 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
 	kmemleak_alloc_recursive(ptr, cachep->object_size, 1, cachep->flags,
 				 flags);
 
-	if (likely(ptr))
+	if (likely(ptr)) {
 		kmemcheck_slab_alloc(cachep, flags, ptr, cachep->object_size);
-
-	if (unlikely((flags & __GFP_ZERO) && ptr))
-		memset(ptr, 0, cachep->object_size);
+		if (unlikely(flags & __GFP_ZERO))
+			memset(ptr, 0, cachep->object_size);
+	}
 
 	return ptr;
 }
@@ -3310,17 +3346,17 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
 				 flags);
 	prefetchw(objp);
 
-	if (likely(objp))
+	if (likely(objp)) {
 		kmemcheck_slab_alloc(cachep, flags, objp, cachep->object_size);
-
-	if (unlikely((flags & __GFP_ZERO) && objp))
-		memset(objp, 0, cachep->object_size);
+		if (unlikely(flags & __GFP_ZERO))
+			memset(objp, 0, cachep->object_size);
+	}
 
 	return objp;
 }
 
 /*
- * Caller needs to acquire correct kmem_list's list_lock
+ * Caller needs to acquire correct kmem_cache_node's list_lock
  */
 static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,
 		       int node)
@@ -3574,11 +3610,6 @@ static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
 	struct kmem_cache *cachep;
 	void *ret;
 
-	/* If you want to save a few bytes .text space: replace
-	 * __ with kmem_.
-	 * Then kmalloc uses the uninlined functions instead of the inline
-	 * functions.
-	 */
 	cachep = kmalloc_slab(size, flags);
 	if (unlikely(ZERO_OR_NULL_PTR(cachep)))
 		return cachep;
@@ -3670,7 +3701,7 @@ EXPORT_SYMBOL(kfree);
 /*
  * This initializes kmem_cache_node or resizes various caches for all nodes.
  */
-static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
+static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp)
 {
 	int node;
 	struct kmem_cache_node *n;
@@ -3726,8 +3757,8 @@ static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
 		}
 
 		kmem_cache_node_init(n);
-		n->next_reap = jiffies + REAPTIMEOUT_LIST3 +
-				((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+		n->next_reap = jiffies + REAPTIMEOUT_NODE +
+				((unsigned long)cachep) % REAPTIMEOUT_NODE;
 		n->shared = new_shared;
 		n->alien = new_alien;
 		n->free_limit = (1 + nr_cpus_node(node)) *
@@ -3813,7 +3844,7 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
 		kfree(ccold);
 	}
 	kfree(new);
-	return alloc_kmemlist(cachep, gfp);
+	return alloc_kmem_cache_node(cachep, gfp);
 }
 
 static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
@@ -3982,7 +4013,7 @@ static void cache_reap(struct work_struct *w)
 		if (time_after(n->next_reap, jiffies))
 			goto next;
 
-		n->next_reap = jiffies + REAPTIMEOUT_LIST3;
+		n->next_reap = jiffies + REAPTIMEOUT_NODE;
 
 		drain_array(searchp, n, n->shared, 0, node);
 
@@ -4003,7 +4034,7 @@ next:
 	next_reap_node();
 out:
 	/* Set up the next iteration */
-	schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_CPUC));
+	schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_AC));
 }
 
 #ifdef CONFIG_SLABINFO
@@ -4210,7 +4241,7 @@ static void handle_slab(unsigned long *n, struct kmem_cache *c,
 
 		for (j = page->active; j < c->num; j++) {
 			/* Skip freed item */
-			if (slab_freelist(page)[j] == i) {
+			if (get_free_obj(page, j) == i) {
 				active = false;
 				break;
 			}