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  mm/slab.c: cleanup outdated comments and unify variables naming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 3db4cb06e32e..388cb1ae6fbc 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;
                         }