From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 6 Jul 2011 03:47:32 +0000 (-0400)
Subject: rculfhash: implement real hash function
X-Git-Tag: v0.7.0~43^2~229
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=732ad076c182b3ad706cd62f8a6694f921e1bb7c;p=userspace-rcu.git

rculfhash: implement real hash function

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/rculfhash.c b/rculfhash.c
index a599961..497a9ea 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -46,7 +46,7 @@
 #define dbg_printf(args...)
 #endif
 
-#define BUCKET_SIZE_RESIZE_THRESHOLD	8
+#define BUCKET_SIZE_RESIZE_THRESHOLD	4
 
 #ifndef max
 #define max(a, b)	((a) > (b) ? (a) : (b))
@@ -62,7 +62,8 @@ struct rcu_table {
 struct rcu_ht {
 	struct rcu_table *t;		/* shared */
 	ht_hash_fct hash_fct;
-	void *hashseed;
+	ht_compare_fct compare_fct;
+	unsigned long hash_seed;
 	pthread_mutex_t resize_mutex;	/* resize mutex: add/del mutex */
 	void (*ht_call_rcu)(struct rcu_head *head,
 		      void (*func)(struct rcu_head *head));
@@ -314,7 +315,8 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
 }
 
 struct rcu_ht *ht_new(ht_hash_fct hash_fct,
-		      void *hashseed,
+		      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)))
@@ -323,7 +325,8 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 
 	ht = calloc(1, sizeof(struct rcu_ht));
 	ht->hash_fct = hash_fct;
-	ht->hashseed = hashseed;
+	ht->compare_fct = compare_fct;
+	ht->hash_seed = hash_seed;
 	ht->ht_call_rcu = ht_call_rcu;
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
@@ -336,13 +339,13 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 	return ht;
 }
 
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key)
+struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 {
 	struct rcu_table *t;
 	struct rcu_ht_node *node;
 	unsigned long hash, reverse_hash;
 
-	hash = ht->hash_fct(ht->hashseed, key);
+	hash = ht->hash_fct(key, key_len, ht->hash_seed);
 	reverse_hash = bit_reverse_ulong(hash);
 
 	t = rcu_dereference(ht->t);
@@ -354,7 +357,7 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key)
 			node = NULL;
 			break;
 		}
-		if (node->key == key) {
+		if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
 			if (is_removed(rcu_dereference(node->next)))
 				node = NULL;
 			break;
@@ -368,7 +371,7 @@ void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
 {
 	struct rcu_table *t;
 
-	node->hash = ht->hash_fct(ht->hashseed, node->key);
+	node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
 	node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
 
 	t = rcu_dereference(ht->t);
@@ -451,7 +454,6 @@ void _do_ht_resize(struct rcu_ht *ht)
 	memcpy(&new_t->tbl, &old_t->tbl,
 	       old_size * sizeof(struct rcu_ht_node *));
 	init_table(ht, new_t, old_size, new_size - old_size);
-	new_t->size = new_size;
 	/* 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);
diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
index d7fe4c8..5935656 100644
--- a/tests/test_urcu_hash.c
+++ b/tests/test_urcu_hash.c
@@ -181,22 +181,148 @@ void rcu_copy_mutex_unlock(void)
 	}
 }
 
+/*
+ * Hash function
+ * Source: http://burtleburtle.net/bob/c/lookup3.c
+ * Originally Public Domain
+ */
+
+#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
+
+#define mix(a, b, c) \
+do { \
+	a -= c; a ^= rot(c,  4); c += b; \
+	b -= a; b ^= rot(a,  6); a += c; \
+	c -= b; c ^= rot(b,  8); b += a; \
+	a -= c; a ^= rot(c, 16); c += b; \
+	b -= a; b ^= rot(a, 19); a += c; \
+	c -= b; c ^= rot(b,  4); b += a; \
+} while (0)
+
+#define final(a, b, c) \
+{ \
+	c ^= b; c -= rot(b, 14); \
+	a ^= c; a -= rot(c, 11); \
+	b ^= a; b -= rot(a, 25); \
+	c ^= b; c -= rot(b, 16); \
+	a ^= c; a -= rot(c,  4);\
+	b ^= a; b -= rot(a, 14); \
+	c ^= b; c -= rot(b, 24); \
+}
+
+static __attribute__((unused))
+uint32_t hash_u32(
+	const uint32_t *k,	/* the key, an array of uint32_t values */
+	size_t length,		/* the length of the key, in uint32_ts */
+	uint32_t initval)	/* the previous hash, or an arbitrary value */
+{
+	uint32_t a, b, c;
+
+	/* Set up the internal state */
+	a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval;
+
+	/*----------------------------------------- handle most of the key */
+	while (length > 3) {
+		a += k[0];
+		b += k[1];
+		c += k[2];
+		mix(a, b, c);
+		length -= 3;
+		k += 3;
+	}
+
+	/*----------------------------------- handle the last 3 uint32_t's */
+	switch (length) {	/* all the case statements fall through */
+	case 3: c += k[2];
+	case 2: b += k[1];
+	case 1: a += k[0];
+		final(a, b, c);
+	case 0:			/* case 0: nothing left to add */
+		break;
+	}
+	/*---------------------------------------------- report the result */
+	return c;
+}
+
+static
+void hashword2(
+	const uint32_t *k,	/* the key, an array of uint32_t values */
+	size_t length,		/* the length of the key, in uint32_ts */
+	uint32_t *pc,		/* IN: seed OUT: primary hash value */
+	uint32_t *pb)		/* IN: more seed OUT: secondary hash value */
+{
+	uint32_t a, b, c;
+
+	/* Set up the internal state */
+	a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc;
+	c += *pb;
+
+	/*----------------------------------------- handle most of the key */
+	while (length > 3) {
+		a += k[0];
+		b += k[1];
+		c += k[2];
+		mix(a, b, c);
+		length -= 3;
+		k += 3;
+	}
+
+	/*----------------------------------- handle the last 3 uint32_t's */
+	switch (length) {	/* all the case statements fall through */
+	case 3: c += k[2];
+	case 2: b += k[1];
+	case 1: a += k[0];
+		final(a, b, c);
+	case 0:			/* case 0: nothing left to add */
+		break;
+	}
+	/*---------------------------------------------- report the result */
+	*pc = c;
+	*pb = b;
+}
+
+#if (CAA_BITS_PER_LONG == 32)
 static
-unsigned long test_hash(void *_hashseed, void *_key)
+unsigned long test_hash(void *_key, size_t length, unsigned long seed)
 {
-	unsigned long seed = (unsigned long) _hashseed;
 	unsigned long key = (unsigned long) _key;
 	unsigned long v;
 
-	v = key ^ seed;
-	v ^= v << 8;
-	v ^= v << 16;
-	v ^= v << 27;
-	v ^= v >> 8;
-	v ^= v >> 16;
-	v ^= v >> 27;
+	assert(length == sizeof(unsigned long));
+	return hash_u32(&v, 1, seed);
+}
+#else
+static
+unsigned long test_hash(void *_key, size_t length, unsigned long seed)
+{
+	union {
+		uint64_t v64;
+		uint32_t v32[2];
+	} v;
+	union {
+		uint64_t v64;
+		uint32_t v32[2];
+	} key;
+
+	assert(length == sizeof(unsigned long));
+	v.v64 = (uint64_t) seed;
+	key.v64 = (uint64_t) _key;
+	hashword2(key.v32, 2, &v.v32[0], &v.v32[1]);
+	return v.v64;
+}
+#endif
 
-	return v;
+static
+unsigned long test_compare(void *key1, size_t key1_len,
+                           void *key2, size_t key2_len)
+{
+	if (unlikely(key1_len != key2_len))
+		return -1;
+	assert(key1_len == sizeof(unsigned long));
+	if (key1 == key2)
+		return 0;
+	else
+		return 1;
 }
 
 void *thr_reader(void *_count)
@@ -219,7 +345,8 @@ void *thr_reader(void *_count)
 	for (;;) {
 		rcu_read_lock();
 		node = ht_lookup(test_ht,
-			(void *)(unsigned long)(rand_r(&rand_lookup) % RAND_POOL));
+			(void *)(unsigned long)(rand_r(&rand_lookup) % RAND_POOL),
+			sizeof(void *));
 		if (node == NULL)
 			lookup_fail++;
 		else
@@ -276,6 +403,7 @@ void *thr_writer(void *_count)
 			rcu_read_lock();
 			ht_node_init(node,
 				(void *)(unsigned long)(rand_r(&rand_lookup) % RAND_POOL),
+				sizeof(void *),
 				(void *) 0x42);
 			ht_add(test_ht, node);
 			rcu_read_unlock();
@@ -284,7 +412,8 @@ void *thr_writer(void *_count)
 			/* May delete */
 			rcu_read_lock();
 			node = ht_lookup(test_ht,
-				(void *)(unsigned long)(rand_r(&rand_lookup) % RAND_POOL));
+				(void *)(unsigned long)(rand_r(&rand_lookup) % RAND_POOL),
+				sizeof(void *));
 			if (node)
 				ret = ht_remove(test_ht, node);
 			else
@@ -424,7 +553,7 @@ int main(int argc, char **argv)
 	tid_writer = malloc(sizeof(*tid_writer) * nr_writers);
 	count_reader = malloc(sizeof(*count_reader) * nr_readers);
 	count_writer = malloc(sizeof(*count_writer) * nr_writers);
-	test_ht = ht_new(test_hash, (void *) 0x42,
+	test_ht = ht_new(test_hash, test_compare, 0x42UL,
 			 HASH_SIZE, call_rcu);
 	next_aff = 0;
 
diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 1aa98c5..94206e3 100644
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -7,6 +7,7 @@
 struct rcu_ht_node {
 	struct rcu_ht_node *next;
 	void *key;
+	size_t key_len;
 	unsigned long hash;
 	unsigned long reverse_hash;
 	unsigned int dummy;
@@ -21,12 +22,17 @@ struct rcu_ht;
  * Ensure reader and writer threads are registered as urcu readers.
  */
 
-typedef unsigned long (*ht_hash_fct)(void *hashseed, void *key);
+typedef unsigned long (*ht_hash_fct)(void *key, size_t length,
+				     unsigned long seed);
+typedef unsigned long (*ht_compare_fct)(void *key1, size_t key1_len,
+				        void *key2, size_t key2_len);
 
 static inline
-void ht_node_init(struct rcu_ht_node *node, void *key, void *value)
+void ht_node_init(struct rcu_ht_node *node, void *key,
+		  size_t key_len, void *value)
 {
 	node->key = key;
+	node->key_len = key_len;
 	node->value = value;
 	node->dummy = 0;
 }
@@ -35,7 +41,8 @@ void ht_node_init(struct rcu_ht_node *node, void *key, void *value)
  * init_size must be power of two.
  */
 struct rcu_ht *ht_new(ht_hash_fct hash_fct,
-		      void *hashseed,
+		      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)));
@@ -43,7 +50,7 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 int ht_destroy(struct rcu_ht *ht);
 
 /* Call with rcu_read_lock held. */
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key);
+struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len);
 
 /* Call with rcu_read_lock held. */
 void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node);