X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=600feecfa8f4f8230eede1683cf79cff14a0333f;hp=46513dfd40562bb7c1e0bb24f39fee3656e378a2;hb=5f74363e048fb82d7ad97a780eadbeb063840787;hpb=14360f1c5d88854a94caa9e6a933c430b38731f4

diff --git a/rculfhash.c b/rculfhash.c
index 46513df..600feec 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -179,6 +179,7 @@
  * tables and machines lacking per-cpu data suppport.
  */
 #define COUNT_COMMIT_ORDER		10
+#define DEFAULT_SPLIT_COUNT_MASK	0xFUL
 #define CHAIN_LEN_TARGET		1
 #define CHAIN_LEN_RESIZE_THRESHOLD	3
 
@@ -221,15 +222,37 @@
 /* Value of the end pointer. Should not interact with flags. */
 #define END_VALUE		NULL
 
+/*
+ * ht_items_count: Split-counters counting the number of node addition
+ * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
+ * is set at hash table creation.
+ *
+ * These are free-running counters, never reset to zero. They count the
+ * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
+ * operations to update the global counter. We choose a power-of-2 value
+ * for the trigger to deal with 32 or 64-bit overflow of the counter.
+ */
 struct ht_items_count {
 	unsigned long add, del;
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
+/*
+ * rcu_level: Contains the per order-index-level dummy node table. The
+ * size of each dummy node table is half the number of hashes contained
+ * in this order (except for order 0). The minimum allocation size
+ * parameter allows combining the dummy node arrays of the lowermost
+ * levels to improve cache locality for small index orders.
+ */
 struct rcu_level {
 	/* Note: manually update allocation length when adding a field */
 	struct _cds_lfht_node nodes[0];
 };
 
+/*
+ * rcu_table: Contains the size and desired new size if a resize
+ * operation is in progress, as well as the statically-sized array of
+ * rcu_level pointers.
+ */
 struct rcu_table {
 	unsigned long size;	/* always a power of 2, shared (RCU) */
 	unsigned long resize_target;
@@ -237,6 +260,11 @@ struct rcu_table {
 	struct rcu_level *tbl[MAX_TABLE_ORDER];
 };
 
+/*
+ * cds_lfht: Top-level data structure representing a lock-free hash
+ * table. Defined in the implementation file to make it be an opaque
+ * cookie to users.
+ */
 struct cds_lfht {
 	struct rcu_table t;
 	cds_lfht_hash_fct hash_fct;
@@ -268,11 +296,20 @@ struct cds_lfht {
 	struct ht_items_count *split_count;	/* split item count */
 };
 
+/*
+ * rcu_resize_work: Contains arguments passed to RCU worker thread
+ * responsible for performing lazy resize.
+ */
 struct rcu_resize_work {
 	struct rcu_head head;
 	struct cds_lfht *ht;
 };
 
+/*
+ * partition_resize_work: Contains arguments passed to worker threads
+ * executing the hash table resize on partitions of the hash table
+ * assigned to each processor's worker thread.
+ */
 struct partition_resize_work {
 	pthread_t thread_id;
 	struct cds_lfht *ht;
@@ -453,7 +490,7 @@ unsigned int fls_u32(uint32_t x)
 
 unsigned int fls_ulong(unsigned long x)
 {
-#if (CAA_BITS_PER_lONG == 32)
+#if (CAA_BITS_PER_LONG == 32)
 	return fls_u32(x);
 #else
 	return fls_u64(x);
@@ -485,25 +522,19 @@ int get_count_order_ulong(unsigned long x)
 }
 
 #ifdef POISON_FREE
-#define poison_free(ptr)				\
-	do {						\
-		memset(ptr, 0x42, sizeof(*(ptr)));	\
-		free(ptr);				\
+#define poison_free(ptr)					\
+	do {							\
+		if (ptr) {					\
+			memset(ptr, 0x42, sizeof(*(ptr)));	\
+			free(ptr);				\
+		}						\
 	} while (0)
 #else
 #define poison_free(ptr)	free(ptr)
 #endif
 
 static
-void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth);
-
-/*
- * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
- * available, then we support hash table item accounting.
- * In the unfortunate event the number of CPUs reported would be
- * inaccurate, we use modulo arithmetic on the number of CPUs we got.
- */
-#if defined(HAVE_SYSCONF)
+void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
 
 static
 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
@@ -512,6 +543,7 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 static long nr_cpus_mask = -1;
 static long split_count_mask = -1;
 
+#if defined(HAVE_SYSCONF)
 static void ht_init_nr_cpus_mask(void)
 {
 	long maxcpus;
@@ -528,27 +560,40 @@ static void ht_init_nr_cpus_mask(void)
 	maxcpus = 1UL << get_count_order_ulong(maxcpus);
 	nr_cpus_mask = maxcpus - 1;
 }
+#else /* #if defined(HAVE_SYSCONF) */
+static void ht_init_nr_cpus_mask(void)
+{
+	nr_cpus_mask = -2;
+}
+#endif /* #else #if defined(HAVE_SYSCONF) */
 
 static
-struct ht_items_count *alloc_split_items_count(void)
+void alloc_split_items_count(struct cds_lfht *ht)
 {
 	struct ht_items_count *count;
 
 	if (nr_cpus_mask == -1)	{
 		ht_init_nr_cpus_mask();
-		split_count_mask = nr_cpus_mask;
+		if (nr_cpus_mask < 0)
+			split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
+		else
+			split_count_mask = nr_cpus_mask;
 	}
 
-	if (split_count_mask < 0)
-		return NULL;
-	else
-		return calloc(split_count_mask + 1, sizeof(*count));
+	assert(split_count_mask >= 0);
+
+	if (ht->flags & CDS_LFHT_ACCOUNTING) {
+		ht->split_count = calloc(split_count_mask + 1, sizeof(*count));
+		assert(ht->split_count);
+	} else {
+		ht->split_count = NULL;
+	}
 }
 
 static
-void free_split_items_count(struct ht_items_count *count)
+void free_split_items_count(struct cds_lfht *ht)
 {
-	poison_free(count);
+	poison_free(ht->split_count);
 }
 
 #if defined(HAVE_SCHED_GETCPU)
@@ -559,7 +604,7 @@ int ht_get_split_count_index(unsigned long hash)
 
 	assert(split_count_mask >= 0);
 	cpu = sched_getcpu();
-	if (unlikely(cpu < 0))
+	if (caa_unlikely(cpu < 0))
 		return hash & split_count_mask;
 	else
 		return cpu & split_count_mask;
@@ -578,11 +623,11 @@ void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
 	unsigned long split_count;
 	int index;
 
-	if (unlikely(!ht->split_count))
+	if (caa_unlikely(!ht->split_count))
 		return;
 	index = ht_get_split_count_index(hash);
 	split_count = uatomic_add_return(&ht->split_count[index].add, 1);
-	if (unlikely(!(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
+	if (caa_unlikely(!(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
 		long count;
 
 		dbg_printf("add split count %lu\n", split_count);
@@ -605,11 +650,11 @@ void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
 	unsigned long split_count;
 	int index;
 
-	if (unlikely(!ht->split_count))
+	if (caa_unlikely(!ht->split_count))
 		return;
 	index = ht_get_split_count_index(hash);
 	split_count = uatomic_add_return(&ht->split_count[index].del, 1);
-	if (unlikely(!(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
+	if (caa_unlikely(!(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
 		long count;
 
 		dbg_printf("del split count %lu\n", split_count);
@@ -632,35 +677,6 @@ void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
 	}
 }
 
-#else /* #if defined(HAVE_SYSCONF) */
-
-static const long nr_cpus_mask = -2;
-static const long split_count_mask = -2;
-
-static
-struct ht_items_count *alloc_split_items_count(void)
-{
-	return NULL;
-}
-
-static
-void free_split_items_count(struct ht_items_count *count)
-{
-}
-
-static
-void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
-{
-}
-
-static
-void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
-{
-}
-
-#endif /* #else #if defined(HAVE_SYSCONF) */
-
-
 static
 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
 {
@@ -679,7 +695,7 @@ void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
 		dbg_printf("WARNING: large chain length: %u.\n",
 			   chain_len);
 	if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
-		cds_lfht_resize_lazy(ht, size,
+		cds_lfht_resize_lazy_grow(ht, size,
 			get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
 }
 
@@ -726,7 +742,8 @@ int is_end(struct cds_lfht_node *node)
 }
 
 static
-unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
+unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
+		unsigned long v)
 {
 	unsigned long old1, old2;
 
@@ -736,7 +753,7 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 		if (old2 >= v)
 			return old2;
 	} while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
-	return v;
+	return old2;
 }
 
 static
@@ -790,12 +807,12 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node
 		 */
 		assert(dummy != node);
 		for (;;) {
-			if (unlikely(is_end(iter)))
+			if (caa_unlikely(is_end(iter)))
 				return;
-			if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
+			if (caa_likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
 				return;
 			next = rcu_dereference(clear_flag(iter)->p.next);
-			if (likely(is_removed(next)))
+			if (caa_likely(is_removed(next)))
 				break;
 			iter_prev = clear_flag(iter);
 			iter = next;
@@ -899,9 +916,9 @@ void _cds_lfht_add(struct cds_lfht *ht,
 		iter = rcu_dereference(iter_prev->p.next);
 		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
 		for (;;) {
-			if (unlikely(is_end(iter)))
+			if (caa_unlikely(is_end(iter)))
 				goto insert;
-			if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
+			if (caa_likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
 				goto insert;
 
 			/* dummy node is the first node of the identical-hash-value chain */
@@ -909,7 +926,7 @@ void _cds_lfht_add(struct cds_lfht *ht,
 				goto insert;
 
 			next = rcu_dereference(clear_flag(iter)->p.next);
-			if (unlikely(is_removed(next)))
+			if (caa_unlikely(is_removed(next)))
 				goto gc_node;
 
 			/* uniquely add */
@@ -999,7 +1016,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
 		struct cds_lfht_node *new_next;
 
 		next = old;
-		if (unlikely(is_removed(next)))
+		if (caa_unlikely(is_removed(next)))
 			return -ENOENT;
 		if (dummy_removal)
 			assert(is_dummy(next));
@@ -1350,6 +1367,7 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	init_size = max(init_size, min_alloc_size);
 	ht = calloc(1, sizeof(struct cds_lfht));
 	assert(ht);
+	ht->flags = flags;
 	ht->hash_fct = hash_fct;
 	ht->compare_fct = compare_fct;
 	ht->hash_seed = hash_seed;
@@ -1362,16 +1380,15 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	ht->cds_lfht_rcu_register_thread = cds_lfht_rcu_register_thread;
 	ht->cds_lfht_rcu_unregister_thread = cds_lfht_rcu_unregister_thread;
 	ht->resize_attr = attr;
-	ht->split_count = alloc_split_items_count();
+	alloc_split_items_count(ht);
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
-	ht->flags = flags;
 	order = get_count_order_ulong(init_size);
 	ht->t.resize_target = 1UL << order;
-	cds_lfht_create_dummy(ht, 1UL << order);
-	ht->t.size = 1UL << order;
 	ht->min_alloc_size = min_alloc_size;
 	ht->min_alloc_order = get_count_order_ulong(min_alloc_size);
+	cds_lfht_create_dummy(ht, 1UL << order);
+	ht->t.size = 1UL << order;
 	return ht;
 }
 
@@ -1392,19 +1409,20 @@ void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
 	node = rcu_dereference(dummy_node->p.next);
 	node = clear_flag(node);
 	for (;;) {
-		if (unlikely(is_end(node))) {
+		if (caa_unlikely(is_end(node))) {
 			node = next = NULL;
 			break;
 		}
-		if (unlikely(node->p.reverse_hash > reverse_hash)) {
+		if (caa_unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = next = NULL;
 			break;
 		}
 		next = rcu_dereference(node->p.next);
-		if (likely(!is_removed(next))
+		assert(node == clear_flag(node));
+		if (caa_likely(!is_removed(next))
 		    && !is_dummy(next)
-		    && clear_flag(node)->p.reverse_hash == reverse_hash
-		    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
+		    && node->p.reverse_hash == reverse_hash
+		    && caa_likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
 				break;
 		}
 		node = clear_flag(next);
@@ -1429,18 +1447,18 @@ void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter)
 	node = clear_flag(next);
 
 	for (;;) {
-		if (unlikely(is_end(node))) {
+		if (caa_unlikely(is_end(node))) {
 			node = next = NULL;
 			break;
 		}
-		if (unlikely(node->p.reverse_hash > reverse_hash)) {
+		if (caa_unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = next = NULL;
 			break;
 		}
 		next = rcu_dereference(node->p.next);
-		if (likely(!is_removed(next))
+		if (caa_likely(!is_removed(next))
 		    && !is_dummy(next)
-		    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
+		    && caa_likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
 				break;
 		}
 		node = clear_flag(next);
@@ -1456,12 +1474,12 @@ void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
 
 	node = clear_flag(iter->next);
 	for (;;) {
-		if (unlikely(is_end(node))) {
+		if (caa_unlikely(is_end(node))) {
 			node = next = NULL;
 			break;
 		}
 		next = rcu_dereference(node->p.next);
-		if (likely(!is_removed(next))
+		if (caa_likely(!is_removed(next))
 		    && !is_dummy(next)) {
 				break;
 		}
@@ -1617,7 +1635,7 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
 	ret = cds_lfht_delete_dummy(ht);
 	if (ret)
 		return ret;
-	free_split_items_count(ht->split_count);
+	free_split_items_count(ht);
 	if (attr)
 		*attr = ht->resize_attr;
 	poison_free(ht);
@@ -1635,7 +1653,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
 	unsigned long nr_dummy = 0;
 
 	*approx_before = 0;
-	if (split_count_mask >= 0) {
+	if (ht->split_count) {
 		int i;
 
 		for (i = 0; i < split_count_mask + 1; i++) {
@@ -1665,7 +1683,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
 	} while (!is_end(node));
 	dbg_printf("number of dummy nodes: %lu\n", nr_dummy);
 	*approx_after = 0;
-	if (split_count_mask >= 0) {
+	if (ht->split_count) {
 		int i;
 
 		for (i = 0; i < split_count_mask + 1; i++) {
@@ -1736,11 +1754,9 @@ void _do_cds_lfht_resize(struct cds_lfht *ht)
 }
 
 static
-unsigned long resize_target_update(struct cds_lfht *ht, unsigned long size,
-				   int growth_order)
+unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
 {
-	return _uatomic_max(&ht->t.resize_target,
-			    size << growth_order);
+	return _uatomic_xchg_monotonic_increase(&ht->t.resize_target, new_size);
 }
 
 static
@@ -1780,15 +1796,13 @@ void do_resize_cb(struct rcu_head *head)
 }
 
 static
-void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth)
+void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
 {
 	struct rcu_resize_work *work;
-	unsigned long target_size;
 
-	target_size = resize_target_update(ht, size, growth);
 	/* Store resize_target before read resize_initiated */
 	cmm_smp_mb();
-	if (!CMM_LOAD_SHARED(ht->t.resize_initiated) && size < target_size) {
+	if (!CMM_LOAD_SHARED(ht->t.resize_initiated)) {
 		uatomic_inc(&ht->in_progress_resize);
 		cmm_smp_mb();	/* increment resize count before load destroy */
 		if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
@@ -1802,31 +1816,47 @@ void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth)
 	}
 }
 
-#if defined(HAVE_SYSCONF)
+static
+void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
+{
+	unsigned long target_size = size << growth;
+
+	if (resize_target_grow(ht, target_size) >= target_size)
+		return;
+
+	__cds_lfht_resize_lazy_launch(ht);
+}
 
+/*
+ * We favor grow operations over shrink. A shrink operation never occurs
+ * if a grow operation is queued for lazy execution. A grow operation
+ * cancels any pending shrink lazy execution.
+ */
 static
 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 				unsigned long count)
 {
-	struct rcu_resize_work *work;
-
 	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
 		return;
-	resize_target_update_count(ht, count);
-	/* Store resize_target before read resize_initiated */
-	cmm_smp_mb();
-	if (!CMM_LOAD_SHARED(ht->t.resize_initiated)) {
-		uatomic_inc(&ht->in_progress_resize);
-		cmm_smp_mb();	/* increment resize count before load destroy */
-		if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
-			uatomic_dec(&ht->in_progress_resize);
+	count = max(count, ht->min_alloc_size);
+	if (count == size)
+		return;		/* Already the right size, no resize needed */
+	if (count > size) {	/* lazy grow */
+		if (resize_target_grow(ht, count) >= count)
 			return;
+	} else {		/* lazy shrink */
+		for (;;) {
+			unsigned long s;
+
+			s = uatomic_cmpxchg(&ht->t.resize_target, size, count);
+			if (s == size)
+				break;	/* no resize needed */
+			if (s > size)
+				return;	/* growing is/(was just) in progress */
+			if (s <= count)
+				return;	/* some other thread do shrink */
+			size = s;
 		}
-		work = malloc(sizeof(*work));
-		work->ht = ht;
-		ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
-		CMM_STORE_SHARED(ht->t.resize_initiated, 1);
 	}
+	__cds_lfht_resize_lazy_launch(ht);
 }
-
-#endif