X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=4a001cf328298d43f16862ece4251ac7e2c43648;hp=380665b106cb4a68ed308fff7638bff3d3406665;hb=554c284ec074d631fc50a2a1d10a2f3201f070f2;hpb=f0c29ed7ca7129056f5c757a9fbcbbfa8c14da44

diff --git a/rculfhash.c b/rculfhash.c
index 380665b..4a001cf 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -1,7 +1,7 @@
 /*
  * rculfhash.c
  *
- * Userspace RCU library - Lock-Free Expandable RCU Hash Table
+ * Userspace RCU library - Lock-Free Resizable RCU Hash Table
  *
  * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
@@ -29,7 +29,7 @@
  *   symposium on Parallel algorithms and architectures, ACM Press,
  *   (2002), 73-82.
  *
- * Some specificities of this Lock-Free Expandable RCU Hash Table
+ * Some specificities of this Lock-Free Resizable RCU Hash Table
  * implementation:
  *
  * - RCU read-side critical section allows readers to perform hash
@@ -48,9 +48,13 @@
  * - An index of dummy nodes is kept. These dummy nodes are the hash
  *   table "buckets", and they are also chained together in the
  *   split-ordered list, which allows recursive expansion.
- * - The resize operation only allows expanding the hash table.
- *   It is triggered either through an API call or automatically by
- *   detecting long chains in the add operation.
+ * - The resize operation for small tables only allows expanding the hash table.
+ *   It is triggered automatically by detecting long chains in the add
+ *   operation.
+ * - The resize operation for larger tables (and available through an
+ *   API) allows both expanding and shrinking the hash table.
+ * - Per-CPU Split-counters are used to keep track of the number of
+ *   nodes within the hash table for automatic resize triggering.
  * - Resize operation initiated by long chain detection is executed by a
  *   call_rcu thread, which keeps lock-freedom of add and remove.
  * - Resize operations are protected by a mutex.
@@ -92,6 +96,39 @@
  * - The per-order dummy node tables contain a compact version of the
  *   hash table nodes. These tables are invariant after they are
  *   populated into the hash table.
+ * 
+ * A bit of ascii art explanation:
+ * 
+ * Order index is the off-by-one compare to the actual power of 2 because 
+ * we use index 0 to deal with the 0 special-case.
+ * 
+ * This shows the nodes for a small table ordered by reversed bits:
+ * 
+ *    bits   reverse
+ * 0  000        000
+ * 4  100        001
+ * 2  010        010
+ * 6  110        011
+ * 1  001        100
+ * 5  101        101
+ * 3  011        110
+ * 7  111        111
+ * 
+ * This shows the nodes in order of non-reversed bits, linked by 
+ * reversed-bit order.
+ * 
+ * order              bits       reverse
+ * 0               0  000        000
+ *                 |
+ * 1               |  1  001        100             <-
+ *                 |  |                              |
+ * 2               |  |  2  010        010           |
+ *                 |  |  |  3  011        110    <-  |
+ *                 |  |  |  |                     |  |
+ * 3               -> |  |  |  4  100        001  |  |
+ *                    -> |  |     5  101        101  |
+ *                       -> |        6  110        011
+ *                          ->          7  111        111
  */
 
 #define _LGPL_SOURCE
@@ -102,6 +139,7 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "config.h"
 #include <urcu.h>
 #include <urcu-call-rcu.h>
 #include <urcu/arch.h>
@@ -118,8 +156,15 @@
 #define dbg_printf(fmt, args...)
 #endif
 
-#define CHAIN_LEN_TARGET		4
-#define CHAIN_LEN_RESIZE_THRESHOLD	8
+/*
+ * Per-CPU split-counters lazily update the global counter each 1024
+ * addition/removal. It automatically keeps track of resize required.
+ * We use the bucket length as indicator for need to expand for small
+ * tables and machines lacking per-cpu data suppport.
+ */
+#define COUNT_COMMIT_ORDER		10
+#define CHAIN_LEN_TARGET		1
+#define CHAIN_LEN_RESIZE_THRESHOLD	3
 
 #ifndef max
 #define max(a, b)	((a) > (b) ? (a) : (b))
@@ -134,28 +179,40 @@
 #define DUMMY_FLAG		(1UL << 1)
 #define FLAGS_MASK		((1UL << 2) - 1)
 
+struct ht_items_count {
+	unsigned long add, remove;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+struct rcu_level {
+	struct rcu_head head;
+	struct _cds_lfht_node nodes[0];
+};
+
 struct rcu_table {
 	unsigned long size;	/* always a power of 2 */
 	unsigned long resize_target;
 	int resize_initiated;
 	struct rcu_head head;
-	struct _rcu_ht_node *tbl[0];
+	struct rcu_level *tbl[0];
 };
 
-struct rcu_ht {
+struct cds_lfht {
 	struct rcu_table *t;		/* shared */
-	ht_hash_fct hash_fct;
-	ht_compare_fct compare_fct;
+	cds_lfht_hash_fct hash_fct;
+	cds_lfht_compare_fct compare_fct;
 	unsigned long hash_seed;
 	pthread_mutex_t resize_mutex;	/* resize mutex: add/del mutex */
 	unsigned int in_progress_resize, in_progress_destroy;
-	void (*ht_call_rcu)(struct rcu_head *head,
+	void (*cds_lfht_call_rcu)(struct rcu_head *head,
 		      void (*func)(struct rcu_head *head));
+	void (*cds_lfht_synchronize_rcu)(void);
+	unsigned long count;		/* global approximate item count */
+	struct ht_items_count *percpu_count;	/* per-cpu item count */
 };
 
 struct rcu_resize_work {
 	struct rcu_head head;
-	struct rcu_ht *ht;
+	struct cds_lfht *ht;
 };
 
 /*
@@ -351,48 +408,208 @@ int get_count_order_ulong(unsigned long x)
 }
 
 static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth);
+void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, 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_SCHED_GETCPU) && defined(HAVE_SYSCONF)
+
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t,
+				unsigned long count);
+
+static long nr_cpus_mask = -1;
+
+static
+struct ht_items_count *alloc_per_cpu_items_count(void)
+{
+	struct ht_items_count *count;
+
+	switch (nr_cpus_mask) {
+	case -2:
+		return NULL;
+	case -1:
+	{
+		long maxcpus;
+
+		maxcpus = sysconf(_SC_NPROCESSORS_CONF);
+		if (maxcpus <= 0) {
+			nr_cpus_mask = -2;
+			return NULL;
+		}
+		/*
+		 * round up number of CPUs to next power of two, so we
+		 * can use & for modulo.
+		 */
+		maxcpus = 1UL << get_count_order_ulong(maxcpus);
+		nr_cpus_mask = maxcpus - 1;
+	}
+		/* Fall-through */
+	default:
+		return calloc(nr_cpus_mask + 1, sizeof(*count));
+	}
+}
+
+static
+void free_per_cpu_items_count(struct ht_items_count *count)
+{
+	free(count);
+}
+
+static
+int ht_get_cpu(void)
+{
+	int cpu;
+
+	assert(nr_cpus_mask >= 0);
+	cpu = sched_getcpu();
+	if (unlikely(cpu < 0))
+		return cpu;
+	else
+		return cpu & nr_cpus_mask;
+}
+
+static
+void ht_count_add(struct cds_lfht *ht, struct rcu_table *t)
+{
+	unsigned long percpu_count;
+	int cpu;
+
+	if (unlikely(!ht->percpu_count))
+		return;
+	cpu = ht_get_cpu();
+	if (unlikely(cpu < 0))
+		return;
+	percpu_count = uatomic_add_return(&ht->percpu_count[cpu].add, 1);
+	if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
+		unsigned long count;
+
+		dbg_printf("add percpu %lu\n", percpu_count);
+		count = uatomic_add_return(&ht->count,
+					   1UL << COUNT_COMMIT_ORDER);
+		/* If power of 2 */
+		if (!(count & (count - 1))) {
+			if ((count >> CHAIN_LEN_RESIZE_THRESHOLD)
+					< t->size)
+				return;
+			dbg_printf("add set global %lu\n", count);
+			cds_lfht_resize_lazy_count(ht, t,
+				count >> (CHAIN_LEN_TARGET - 1));
+		}
+	}
+}
+
+static
+void ht_count_remove(struct cds_lfht *ht, struct rcu_table *t)
+{
+	unsigned long percpu_count;
+	int cpu;
+
+	if (unlikely(!ht->percpu_count))
+		return;
+	cpu = ht_get_cpu();
+	if (unlikely(cpu < 0))
+		return;
+	percpu_count = uatomic_add_return(&ht->percpu_count[cpu].remove, -1);
+	if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
+		unsigned long count;
+
+		dbg_printf("remove percpu %lu\n", percpu_count);
+		count = uatomic_add_return(&ht->count,
+					   -(1UL << COUNT_COMMIT_ORDER));
+		/* If power of 2 */
+		if (!(count & (count - 1))) {
+			if ((count >> CHAIN_LEN_RESIZE_THRESHOLD)
+					>= t->size)
+				return;
+			dbg_printf("remove set global %lu\n", count);
+			cds_lfht_resize_lazy_count(ht, t,
+				count >> (CHAIN_LEN_TARGET - 1));
+		}
+	}
+}
+
+#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
+
+static const long nr_cpus_mask = -1;
+
+static
+struct ht_items_count *alloc_per_cpu_items_count(void)
+{
+	return NULL;
+}
+
+static
+void free_per_cpu_items_count(struct ht_items_count *count)
+{
+}
+
+static
+void ht_count_add(struct cds_lfht *ht, struct rcu_table *t)
+{
+}
+
+static
+void ht_count_remove(struct cds_lfht *ht, struct rcu_table *t)
+{
+}
+
+#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
+
 
 static
-void check_resize(struct rcu_ht *ht, struct rcu_table *t,
+void check_resize(struct cds_lfht *ht, struct rcu_table *t,
 		  uint32_t chain_len)
 {
+	unsigned long count;
+
+	count = uatomic_read(&ht->count);
+	/*
+	 * Use bucket-local length for small table expand and for
+	 * environments lacking per-cpu data support.
+	 */
+	if (count >= (1UL << COUNT_COMMIT_ORDER))
+		return;
 	if (chain_len > 100)
 		dbg_printf("WARNING: large chain length: %u.\n",
 			   chain_len);
 	if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
-		ht_resize_lazy(ht, t,
+		cds_lfht_resize_lazy(ht, t,
 			get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
 }
 
 static
-struct rcu_ht_node *clear_flag(struct rcu_ht_node *node)
+struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
 {
-	return (struct rcu_ht_node *) (((unsigned long) node) & ~FLAGS_MASK);
+	return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
 }
 
 static
-int is_removed(struct rcu_ht_node *node)
+int is_removed(struct cds_lfht_node *node)
 {
 	return ((unsigned long) node) & REMOVED_FLAG;
 }
 
 static
-struct rcu_ht_node *flag_removed(struct rcu_ht_node *node)
+struct cds_lfht_node *flag_removed(struct cds_lfht_node *node)
 {
-	return (struct rcu_ht_node *) (((unsigned long) node) | REMOVED_FLAG);
+	return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG);
 }
 
 static
-int is_dummy(struct rcu_ht_node *node)
+int is_dummy(struct cds_lfht_node *node)
 {
 	return ((unsigned long) node) & DUMMY_FLAG;
 }
 
 static
-struct rcu_ht_node *flag_dummy(struct rcu_ht_node *node)
+struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node)
 {
-	return (struct rcu_ht_node *) (((unsigned long) node) | DUMMY_FLAG);
+	return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG);
 }
  
 static
@@ -409,13 +626,29 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 	return v;
 }
 
+static
+void cds_lfht_free_table_cb(struct rcu_head *head)
+{
+	struct rcu_table *t =
+		caa_container_of(head, struct rcu_table, head);
+	free(t);
+}
+
+static
+void cds_lfht_free_level(struct rcu_head *head)
+{
+	struct rcu_level *l =
+		caa_container_of(head, struct rcu_level, head);
+	free(l);
+}
+
 /*
  * Remove all logically deleted nodes from a bucket up to a certain node key.
  */
 static
-void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
+void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node)
 {
-	struct rcu_ht_node *iter_prev, *iter, *next, *new_next;
+	struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
 
 	for (;;) {
 		iter_prev = dummy;
@@ -443,12 +676,12 @@ void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
 }
 
 static
-struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
-			    struct rcu_ht_node *node, int unique, int dummy)
+struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, struct rcu_table *t,
+				struct cds_lfht_node *node, int unique, int dummy)
 {
-	struct rcu_ht_node *iter_prev, *iter, *next, *new_node, *new_next,
+	struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
 			*dummy_node;
-	struct _rcu_ht_node *lookup;
+	struct _cds_lfht_node *lookup;
 	unsigned long hash, index, order;
 
 	if (!t->size) {
@@ -466,8 +699,8 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
 		 */
 		index = hash & (t->size - 1);
 		order = get_count_order_ulong(index + 1);
-		lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
-		iter_prev = (struct rcu_ht_node *) lookup;
+		lookup = &t->tbl[order]->nodes[index & ((!order ? 0 : (1UL << (order - 1))) - 1)];
+		iter_prev = (struct cds_lfht_node *) lookup;
 		/* We can always skip the dummy node initially */
 		iter = rcu_dereference(iter_prev->p.next);
 		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
@@ -522,17 +755,18 @@ gc_end:
 	/* Garbage collect logically removed nodes in the bucket */
 	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
-	dummy_node = (struct rcu_ht_node *) lookup;
-	_ht_gc_bucket(dummy_node, node);
+	lookup = &t->tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
+	dummy_node = (struct cds_lfht_node *) lookup;
+	_cds_lfht_gc_bucket(dummy_node, node);
 	return node;
 }
 
 static
-int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+int _cds_lfht_remove(struct cds_lfht *ht, struct rcu_table *t,
+		struct cds_lfht_node *node, int dummy_removal)
 {
-	struct rcu_ht_node *dummy, *next, *old;
-	struct _rcu_ht_node *lookup;
+	struct cds_lfht_node *dummy, *next, *old;
+	struct _cds_lfht_node *lookup;
 	int flagged = 0;
 	unsigned long hash, index, order;
 
@@ -542,7 +776,10 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 		next = old;
 		if (unlikely(is_removed(next)))
 			goto end;
-		assert(!is_dummy(next));
+		if (dummy_removal)
+			assert(is_dummy(next));
+		else
+			assert(!is_dummy(next));
 		old = uatomic_cmpxchg(&node->p.next, next,
 				      flag_removed(next));
 	} while (old != next);
@@ -550,17 +787,21 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 	/* We performed the (logical) deletion. */
 	flagged = 1;
 
+	if (dummy_removal)
+		node = clear_flag(node);
+
 	/*
 	 * Ensure that the node is not visible to readers anymore: lookup for
 	 * the node, and remove it (along with any other logically removed node)
 	 * if found.
 	 */
 	hash = bit_reverse_ulong(node->p.reverse_hash);
+	assert(t->size > 0);
 	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
-	dummy = (struct rcu_ht_node *) lookup;
-	_ht_gc_bucket(dummy, node);
+	lookup = &t->tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
+	dummy = (struct cds_lfht_node *) lookup;
+	_cds_lfht_gc_bucket(dummy, node);
 end:
 	/*
 	 * Only the flagging action indicated that we (and no other)
@@ -574,7 +815,7 @@ end:
 }
 
 static
-void init_table(struct rcu_ht *ht, struct rcu_table *t,
+void init_table(struct cds_lfht *ht, struct rcu_table *t,
 		unsigned long first_order, unsigned long len_order)
 {
 	unsigned long i, end_order;
@@ -588,15 +829,17 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
 
 		len = !i ? 1 : 1UL << (i - 1);
 		dbg_printf("init order %lu len: %lu\n", i, len);
-		t->tbl[i] = calloc(len, sizeof(struct _rcu_ht_node));
+		t->tbl[i] = calloc(1, sizeof(struct rcu_level)
+				+ (len * sizeof(struct _cds_lfht_node)));
 		for (j = 0; j < len; j++) {
+			struct cds_lfht_node *new_node =
+				(struct cds_lfht_node *) &t->tbl[i]->nodes[j];
+
 			dbg_printf("init entry: i %lu j %lu hash %lu\n",
 				   i, j, !i ? 0 : (1UL << (i - 1)) + j);
-			struct rcu_ht_node *new_node =
-				(struct rcu_ht_node *) &t->tbl[i][j];
 			new_node->p.reverse_hash =
 				bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
-			(void) _ht_add(ht, t, new_node, 0, 1);
+			(void) _cds_lfht_add(ht, t, new_node, 0, 1);
 			if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 				break;
 		}
@@ -610,27 +853,73 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
 	t->resize_initiated = 0;
 }
 
-struct rcu_ht *ht_new(ht_hash_fct hash_fct,
-		      ht_compare_fct compare_fct,
-		      unsigned long hash_seed,
-		      unsigned long init_size,
-		      void (*ht_call_rcu)(struct rcu_head *head,
-				void (*func)(struct rcu_head *head)))
+static
+void fini_table(struct cds_lfht *ht, struct rcu_table *t,
+		unsigned long first_order, unsigned long len_order)
 {
-	struct rcu_ht *ht;
+	long i, end_order;
+
+	dbg_printf("fini table: first_order %lu end_order %lu\n",
+		   first_order, first_order + len_order);
+	end_order = first_order + len_order;
+	assert(first_order > 0);
+	assert(t->size == (1UL << (end_order - 1)));
+	for (i = end_order - 1; i >= first_order; i--) {
+		unsigned long j, len;
+
+		len = !i ? 1 : 1UL << (i - 1);
+		dbg_printf("fini order %lu len: %lu\n", i, len);
+		/* Update table size */
+		t->size = 1UL << (i - 1);
+		/* Unlink */
+		for (j = 0; j < len; j++) {
+			struct cds_lfht_node *new_node =
+				(struct cds_lfht_node *) &t->tbl[i]->nodes[j];
+
+			dbg_printf("fini entry: i %lu j %lu hash %lu\n",
+				   i, j, !i ? 0 : (1UL << (i - 1)) + j);
+			new_node->p.reverse_hash =
+				bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
+			(void) _cds_lfht_remove(ht, t, new_node, 1);
+			if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+				break;
+		}
+		ht->cds_lfht_call_rcu(&t->tbl[i]->head, cds_lfht_free_level);
+		dbg_printf("fini new size: %lu\n", t->size);
+		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+			break;
+	}
+	t->resize_target = t->size;
+	t->resize_initiated = 0;
+}
+
+struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
+			cds_lfht_compare_fct compare_fct,
+			unsigned long hash_seed,
+			unsigned long init_size,
+			void (*cds_lfht_call_rcu)(struct rcu_head *head,
+					void (*func)(struct rcu_head *head)),
+			void (*cds_lfht_synchronize_rcu)(void))
+{
+	struct cds_lfht *ht;
 	unsigned long order;
 
-	ht = calloc(1, sizeof(struct rcu_ht));
+	/* init_size must be power of two */
+	if (init_size && (init_size & (init_size - 1)))
+		return NULL;
+	ht = calloc(1, sizeof(struct cds_lfht));
 	ht->hash_fct = hash_fct;
 	ht->compare_fct = compare_fct;
 	ht->hash_seed = hash_seed;
-	ht->ht_call_rcu = ht_call_rcu;
+	ht->cds_lfht_call_rcu = cds_lfht_call_rcu;
+	ht->cds_lfht_synchronize_rcu = cds_lfht_synchronize_rcu;
 	ht->in_progress_resize = 0;
+	ht->percpu_count = alloc_per_cpu_items_count();
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
 	order = get_count_order_ulong(max(init_size, 1)) + 1;
-	ht->t = calloc(1, sizeof(struct rcu_table)
-		       + (order * sizeof(struct _rcu_ht_node *)));
+	ht->t = calloc(1, sizeof(struct cds_lfht)
+		       + (order * sizeof(struct rcu_level *)));
 	ht->t->size = 0;
 	pthread_mutex_lock(&ht->resize_mutex);
 	init_table(ht, ht->t, 0, order);
@@ -638,11 +927,11 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 	return ht;
 }
 
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
+struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len)
 {
 	struct rcu_table *t;
-	struct rcu_ht_node *node, *next;
-	struct _rcu_ht_node *lookup;
+	struct cds_lfht_node *node, *next;
+	struct _cds_lfht_node *lookup;
 	unsigned long hash, reverse_hash, index, order;
 
 	hash = ht->hash_fct(key, key_len, ht->hash_seed);
@@ -651,10 +940,10 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 	t = rcu_dereference(ht->t);
 	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
+	lookup = &t->tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)];
 	dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
-		   hash, index, order, index & ((1UL << (order - 1)) - 1));
-	node = (struct rcu_ht_node *) lookup;
+		   hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
+	node = (struct cds_lfht_node *) lookup;
 	for (;;) {
 		if (unlikely(!node))
 			break;
@@ -674,7 +963,40 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 	return node;
 }
 
-void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
+struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht,
+				struct cds_lfht_node *node)
+{
+	struct cds_lfht_node *next;
+	unsigned long reverse_hash;
+	void *key;
+	size_t key_len;
+
+	reverse_hash = node->p.reverse_hash;
+	key = node->key;
+	key_len = node->key_len;
+	next = rcu_dereference(node->p.next);
+	node = clear_flag(next);
+
+	for (;;) {
+		if (unlikely(!node))
+			break;
+		if (unlikely(node->p.reverse_hash > reverse_hash)) {
+			node = NULL;
+			break;
+		}
+		next = rcu_dereference(node->p.next);
+		if (likely(!is_removed(next))
+		    && !is_dummy(next)
+		    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
+				break;
+		}
+		node = clear_flag(next);
+	}
+	assert(!node || !is_dummy(rcu_dereference(node->p.next)));
+	return node;
+}
+
+void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
 {
 	struct rcu_table *t;
 	unsigned long hash;
@@ -683,41 +1005,51 @@ void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
 	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	t = rcu_dereference(ht->t);
-	(void) _ht_add(ht, t, node, 0, 0);
+	(void) _cds_lfht_add(ht, t, node, 0, 0);
+	ht_count_add(ht, t);
 }
 
-struct rcu_ht_node *ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
+struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
+					struct cds_lfht_node *node)
 {
 	struct rcu_table *t;
 	unsigned long hash;
+	struct cds_lfht_node *ret;
 
 	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
 	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	t = rcu_dereference(ht->t);
-	return _ht_add(ht, t, node, 1, 0);
+	ret = _cds_lfht_add(ht, t, node, 1, 0);
+	if (ret != node)
+		ht_count_add(ht, t);
+	return ret;
 }
 
-int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
+int cds_lfht_remove(struct cds_lfht *ht, struct cds_lfht_node *node)
 {
 	struct rcu_table *t;
+	int ret;
 
 	t = rcu_dereference(ht->t);
-	return _ht_remove(ht, t, node);
+	ret = _cds_lfht_remove(ht, t, node, 0);
+	if (!ret)
+		ht_count_remove(ht, t);
+	return ret;
 }
 
 static
-int ht_delete_dummy(struct rcu_ht *ht)
+int cds_lfht_delete_dummy(struct cds_lfht *ht)
 {
 	struct rcu_table *t;
-	struct rcu_ht_node *node;
-	struct _rcu_ht_node *lookup;
+	struct cds_lfht_node *node;
+	struct _cds_lfht_node *lookup;
 	unsigned long order, i;
 
 	t = ht->t;
 	/* Check that the table is empty */
-	lookup = &t->tbl[0][0];
-	node = (struct rcu_ht_node *) lookup;
+	lookup = &t->tbl[0]->nodes[0];
+	node = (struct cds_lfht_node *) lookup;
 	do {
 		node = clear_flag(node)->p.next;
 		if (!is_dummy(node))
@@ -732,8 +1064,8 @@ int ht_delete_dummy(struct rcu_ht *ht)
 		for (i = 0; i < len; i++) {
 			dbg_printf("delete order %lu i %lu hash %lu\n",
 				order, i,
-				bit_reverse_ulong(t->tbl[order][i].reverse_hash));
-			assert(is_dummy(t->tbl[order][i].next));
+				bit_reverse_ulong(t->tbl[order]->nodes[i].reverse_hash));
+			assert(is_dummy(t->tbl[order]->nodes[i].next));
 		}
 		free(t->tbl[order]);
 	}
@@ -744,7 +1076,7 @@ int ht_delete_dummy(struct rcu_ht *ht)
  * Should only be called when no more concurrent readers nor writers can
  * possibly access the table.
  */
-int ht_destroy(struct rcu_ht *ht)
+int cds_lfht_destroy(struct cds_lfht *ht)
 {
 	int ret;
 
@@ -752,21 +1084,22 @@ int ht_destroy(struct rcu_ht *ht)
 	CMM_STORE_SHARED(ht->in_progress_destroy, 1);
 	while (uatomic_read(&ht->in_progress_resize))
 		poll(NULL, 0, 100);	/* wait for 100ms */
-	ret = ht_delete_dummy(ht);
+	ret = cds_lfht_delete_dummy(ht);
 	if (ret)
 		return ret;
 	free(ht->t);
+	free_per_cpu_items_count(ht->percpu_count);
 	free(ht);
 	return ret;
 }
 
-void ht_count_nodes(struct rcu_ht *ht,
+void cds_lfht_count_nodes(struct cds_lfht *ht,
 		unsigned long *count,
 		unsigned long *removed)
 {
 	struct rcu_table *t;
-	struct rcu_ht_node *node, *next;
-	struct _rcu_ht_node *lookup;
+	struct cds_lfht_node *node, *next;
+	struct _cds_lfht_node *lookup;
 	unsigned long nr_dummy = 0;
 
 	*count = 0;
@@ -774,8 +1107,8 @@ void ht_count_nodes(struct rcu_ht *ht,
 
 	t = rcu_dereference(ht->t);
 	/* Count non-dummy nodes in the table */
-	lookup = &t->tbl[0][0];
-	node = (struct rcu_ht_node *) lookup;
+	lookup = &t->tbl[0]->nodes[0];
+	node = (struct cds_lfht_node *) lookup;
 	do {
 		next = rcu_dereference(node->p.next);
 		if (is_removed(next)) {
@@ -790,40 +1123,83 @@ void ht_count_nodes(struct rcu_ht *ht,
 	dbg_printf("number of dummy nodes: %lu\n", nr_dummy);
 }
 
+/* called with resize mutex held */
 static
-void ht_free_table_cb(struct rcu_head *head)
+void _do_cds_lfht_grow(struct cds_lfht *ht, struct rcu_table *old_t,
+		unsigned long old_size, unsigned long new_size)
 {
-	struct rcu_table *t =
-		caa_container_of(head, struct rcu_table, head);
-	free(t);
+	unsigned long old_order, new_order;
+	struct rcu_table *new_t;
+
+	old_order = get_count_order_ulong(old_size) + 1;
+	new_order = get_count_order_ulong(new_size) + 1;
+	printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
+	       old_size, old_order, new_size, new_order);
+	new_t = malloc(sizeof(struct cds_lfht)
+			+ (new_order * sizeof(struct rcu_level *)));
+	assert(new_size > old_size);
+	memcpy(&new_t->tbl, &old_t->tbl,
+	       old_order * sizeof(struct rcu_level *));
+	init_table(ht, new_t, old_order, new_order - old_order);
+	/* Changing table and size atomically wrt lookups */
+	rcu_assign_pointer(ht->t, new_t);
+	ht->cds_lfht_call_rcu(&old_t->head, cds_lfht_free_table_cb);
 }
 
 /* called with resize mutex held */
 static
-void _do_ht_resize(struct rcu_ht *ht)
+void _do_cds_lfht_shrink(struct cds_lfht *ht, struct rcu_table *old_t,
+		unsigned long old_size, unsigned long new_size)
 {
-	unsigned long new_size, old_size, old_order, new_order;
-	struct rcu_table *new_t, *old_t;
+	unsigned long old_order, new_order;
+	struct rcu_table *new_t;
 
-	old_t = ht->t;
-	old_size = old_t->size;
+	new_size = max(new_size, 1);
 	old_order = get_count_order_ulong(old_size) + 1;
-
-	new_size = CMM_LOAD_SHARED(old_t->resize_target);
-	if (old_size == new_size)
-		return;
 	new_order = get_count_order_ulong(new_size) + 1;
-	dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
+	printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
 	       old_size, old_order, new_size, new_order);
-	new_t = malloc(sizeof(struct rcu_table)
-			+ (new_order * sizeof(struct _rcu_ht_node *)));
-	assert(new_size > old_size);
+	new_t = malloc(sizeof(struct cds_lfht)
+			+ (new_order * sizeof(struct rcu_level *)));
+	assert(new_size < old_size);
 	memcpy(&new_t->tbl, &old_t->tbl,
-	       old_order * sizeof(struct _rcu_ht_node *));
-	init_table(ht, new_t, old_order, new_order - old_order);
+	       new_order * sizeof(struct rcu_level *));
+	new_t->size = !new_order ? 1 : (1UL << (new_order - 1));
+	new_t->resize_target = new_t->size;
+	new_t->resize_initiated = 0;
+
 	/* Changing table and size atomically wrt lookups */
 	rcu_assign_pointer(ht->t, new_t);
-	ht->ht_call_rcu(&old_t->head, ht_free_table_cb);
+
+	/*
+	 * We need to wait for all reader threads to reach Q.S. (and
+	 * thus use the new table for lookups) before we can start
+	 * releasing the old dummy nodes.
+	 */
+	ht->cds_lfht_synchronize_rcu();
+
+	/* Unlink and remove all now-unused dummy node pointers. */
+	fini_table(ht, old_t, new_order, old_order - new_order);
+	ht->cds_lfht_call_rcu(&old_t->head, cds_lfht_free_table_cb);
+}
+
+
+/* called with resize mutex held */
+static
+void _do_cds_lfht_resize(struct cds_lfht *ht)
+{
+	unsigned long new_size, old_size;
+	struct rcu_table *old_t;
+
+	old_t = ht->t;
+	old_size = old_t->size;
+	new_size = CMM_LOAD_SHARED(old_t->resize_target);
+	if (old_size < new_size)
+		_do_cds_lfht_grow(ht, old_t, old_size, new_size);
+	else if (old_size > new_size)
+		_do_cds_lfht_shrink(ht, old_t, old_size, new_size);
+	else
+		CMM_STORE_SHARED(old_t->resize_initiated, 0);
 }
 
 static
@@ -834,26 +1210,24 @@ unsigned long resize_target_update(struct rcu_table *t,
 			    t->size << growth_order);
 }
 
-void ht_resize(struct rcu_ht *ht, int growth)
+static
+unsigned long resize_target_update_count(struct rcu_table *t,
+				   unsigned long count)
+{
+	count = max(count, 1);
+	return uatomic_set(&t->resize_target, count);
+}
+
+void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
 {
 	struct rcu_table *t = rcu_dereference(ht->t);
 	unsigned long target_size;
 
-	if (growth < 0) {
-		/*
-		 * Silently refuse to shrink hash table. (not supported)
-		 */
-		dbg_printf("shrinking hash table not supported.\n");
-		return;
-	}
-
-	target_size = resize_target_update(t, growth);
-	if (t->size < target_size) {
-		CMM_STORE_SHARED(t->resize_initiated, 1);
-		pthread_mutex_lock(&ht->resize_mutex);
-		_do_ht_resize(ht);
-		pthread_mutex_unlock(&ht->resize_mutex);
-	}
+	target_size = resize_target_update_count(t, new_size);
+	CMM_STORE_SHARED(t->resize_initiated, 1);
+	pthread_mutex_lock(&ht->resize_mutex);
+	_do_cds_lfht_resize(ht);
+	pthread_mutex_unlock(&ht->resize_mutex);
 }
 
 static
@@ -861,10 +1235,10 @@ void do_resize_cb(struct rcu_head *head)
 {
 	struct rcu_resize_work *work =
 		caa_container_of(head, struct rcu_resize_work, head);
-	struct rcu_ht *ht = work->ht;
+	struct cds_lfht *ht = work->ht;
 
 	pthread_mutex_lock(&ht->resize_mutex);
-	_do_ht_resize(ht);
+	_do_cds_lfht_resize(ht);
 	pthread_mutex_unlock(&ht->resize_mutex);
 	free(work);
 	cmm_smp_mb();	/* finish resize before decrement */
@@ -872,7 +1246,7 @@ void do_resize_cb(struct rcu_head *head)
 }
 
 static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
+void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth)
 {
 	struct rcu_resize_work *work;
 	unsigned long target_size;
@@ -883,7 +1257,29 @@ void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
 		cmm_smp_mb();	/* increment resize count before calling it */
 		work = malloc(sizeof(*work));
 		work->ht = ht;
-		ht->ht_call_rcu(&work->head, do_resize_cb);
+		ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
 		CMM_STORE_SHARED(t->resize_initiated, 1);
 	}
 }
+
+#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
+
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t,
+				unsigned long count)
+{
+	struct rcu_resize_work *work;
+	unsigned long target_size;
+
+	target_size = resize_target_update_count(t, count);
+	if (!CMM_LOAD_SHARED(t->resize_initiated)) {
+		uatomic_inc(&ht->in_progress_resize);
+		cmm_smp_mb();	/* increment resize count before calling it */
+		work = malloc(sizeof(*work));
+		work->ht = ht;
+		ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
+		CMM_STORE_SHARED(t->resize_initiated, 1);
+	}
+}
+
+#endif