[dpdk-dev] [PATCH v3] hash table: add an iterator over conflicting entries

[Qiaobin Fu <qiaobinf@bu.edu>]

Function rte_hash_iterate_conflict_entries() iterates over
the entries that conflict with an incoming entry.

Iterating over conflicting entries enables one to decide
if the incoming entry is more valuable than the entries already
in the hash table. This is particularly useful after
an insertion failure.

v3:
* Make the rte_hash_iterate() API similar to
  rte_hash_iterate_conflict_entries()

v2:
* Fix the style issue

* Make the API more universal

Signed-off-by: Qiaobin Fu <qiaobinf@bu.edu>
Reviewed-by: Cody Doucette <doucette@bu.edu>
Reviewed-by: Michel Machado <michel@digirati.com.br>
Reviewed-by: Keith Wiles <keith.wiles@intel.com>
Reviewed-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
---
 lib/librte_hash/rte_cuckoo_hash.c    | 127 +++++++++++++++++++++++----
 lib/librte_hash/rte_hash.h           |  69 +++++++++++++--
 lib/librte_hash/rte_hash_version.map |   8 ++
 test/test/test_hash.c                |   7 +-
 test/test/test_hash_multiwriter.c    |   8 +-
 5 files changed, 194 insertions(+), 25 deletions(-)

diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index a07543a29..8a2e76ff1 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -1120,43 +1120,140 @@ rte_hash_lookup_bulk_data(const struct rte_hash *h, const void **keys,
 	return __builtin_popcountl(*hit_mask);
 }
 
+/* istate stands for internal state. */
+struct rte_hash_iterator_istate {
+	const struct rte_hash *h;
+	uint32_t              next;
+	uint32_t              total_entries;
+};
+
+int32_t
+rte_hash_iterator_init(const struct rte_hash *h,
+	struct rte_hash_iterator_state *state)
+{
+	struct rte_hash_iterator_istate *__state;
+
+	RETURN_IF_TRUE(((h == NULL) || (state == NULL)), -EINVAL);
+
+	__state = (struct rte_hash_iterator_istate *)state;
+	__state->h = h;
+	__state->next = 0;
+	__state->total_entries = h->num_buckets * RTE_HASH_BUCKET_ENTRIES;
+
+	return 0;
+}
+
 int32_t
-rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32_t *next)
+rte_hash_iterate(
+	struct rte_hash_iterator_state *state, const void **key, void **data)
 {
+	struct rte_hash_iterator_istate *__state;
 	uint32_t bucket_idx, idx, position;
 	struct rte_hash_key *next_key;
 
-	RETURN_IF_TRUE(((h == NULL) || (next == NULL)), -EINVAL);
+	RETURN_IF_TRUE(((state == NULL) || (key == NULL) ||
+		(data == NULL)), -EINVAL);
+
+	__state = (struct rte_hash_iterator_istate *)state;
 
-	const uint32_t total_entries = h->num_buckets * RTE_HASH_BUCKET_ENTRIES;
 	/* Out of bounds */
-	if (*next >= total_entries)
+	if (__state->next >= __state->total_entries)
 		return -ENOENT;
 
 	/* Calculate bucket and index of current iterator */
-	bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
-	idx = *next % RTE_HASH_BUCKET_ENTRIES;
+	bucket_idx = __state->next / RTE_HASH_BUCKET_ENTRIES;
+	idx = __state->next % RTE_HASH_BUCKET_ENTRIES;
 
 	/* If current position is empty, go to the next one */
-	while (h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) {
-		(*next)++;
+	while (__state->h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) {
+		__state->next++;
 		/* End of table */
-		if (*next == total_entries)
+		if (__state->next == __state->total_entries)
 			return -ENOENT;
-		bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
-		idx = *next % RTE_HASH_BUCKET_ENTRIES;
+		bucket_idx = __state->next / RTE_HASH_BUCKET_ENTRIES;
+		idx = __state->next % RTE_HASH_BUCKET_ENTRIES;
 	}
 
 	/* Get position of entry in key table */
-	position = h->buckets[bucket_idx].key_idx[idx];
-	next_key = (struct rte_hash_key *) ((char *)h->key_store +
-				position * h->key_entry_size);
+	position = __state->h->buckets[bucket_idx].key_idx[idx];
+	next_key = (struct rte_hash_key *) ((char *)__state->h->key_store +
+				position * __state->h->key_entry_size);
 	/* Return key and data */
 	*key = next_key->key;
 	*data = next_key->pdata;
 
 	/* Increment iterator */
-	(*next)++;
+	__state->next++;
 
 	return position - 1;
 }
+
+struct rte_hash_iterator_conflict_entries_istate {
+	const struct rte_hash *h;
+	uint32_t              vnext;
+	uint32_t              primary_bidx;
+	uint32_t              secondary_bidx;
+};
+
+int32_t __rte_experimental
+rte_hash_iterator_conflict_entries_init_with_hash(const struct rte_hash *h,
+	hash_sig_t sig, struct rte_hash_iterator_state *state)
+{
+	struct rte_hash_iterator_conflict_entries_istate *__state;
+
+	RETURN_IF_TRUE(((h == NULL) || (state == NULL)), -EINVAL);
+
+	__state = (struct rte_hash_iterator_conflict_entries_istate *)state;
+	__state->h = h;
+	__state->vnext = 0;
+
+	/* Get the primary bucket index given the precomputed hash value. */
+	__state->primary_bidx = sig & h->bucket_bitmask;
+	/* Get the secondary bucket index given the precomputed hash value. */
+	__state->secondary_bidx =
+		rte_hash_secondary_hash(sig) & h->bucket_bitmask;
+
+	return 0;
+}
+
+int32_t __rte_experimental
+rte_hash_iterate_conflict_entries(
+	struct rte_hash_iterator_state *state, const void **key, void **data)
+{
+	struct rte_hash_iterator_conflict_entries_istate *__state;
+
+	RETURN_IF_TRUE(((state == NULL) || (key == NULL) ||
+		(data == NULL)), -EINVAL);
+
+	__state = (struct rte_hash_iterator_conflict_entries_istate *)state;
+
+	while (__state->vnext < RTE_HASH_BUCKET_ENTRIES * 2) {
+		uint32_t bidx = __state->vnext < RTE_HASH_BUCKET_ENTRIES ?
+			__state->primary_bidx : __state->secondary_bidx;
+		uint32_t next = __state->vnext & (RTE_HASH_BUCKET_ENTRIES - 1);
+		uint32_t position = __state->h->buckets[bidx].key_idx[next];
+		struct rte_hash_key *next_key;
+
+		/* Increment iterator. */
+		__state->vnext++;
+
+		/*
+		 * The test below is unlikely because this iterator is meant
+		 * to be used after a failed insert.
+		 * */
+		if (unlikely(position == EMPTY_SLOT))
+			continue;
+
+		/* Get the entry in key table. */
+		next_key = (struct rte_hash_key *) (
+			(char *)__state->h->key_store +
+			position * __state->h->key_entry_size);
+		/* Return key and data. */
+		*key = next_key->key;
+		*data = next_key->pdata;
+
+		return position - 1;
+	}
+
+	return -ENOENT;
+}
diff --git a/lib/librte_hash/rte_hash.h b/lib/librte_hash/rte_hash.h
index f71ca9fbf..e3e2bbecb 100644
--- a/lib/librte_hash/rte_hash.h
+++ b/lib/librte_hash/rte_hash.h
@@ -14,6 +14,8 @@
 #include <stdint.h>
 #include <stddef.h>
 
+#include <rte_compat.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -61,6 +63,11 @@ struct rte_hash_parameters {
 /** @internal A hash table structure. */
 struct rte_hash;
 
+/** @internal A hash table iterator state structure. */
+struct rte_hash_iterator_state {
+	uint8_t space[64];
+} __rte_cache_aligned;
+
 /**
  * Create a new hash table.
  *
@@ -399,26 +406,76 @@ rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 		      uint32_t num_keys, int32_t *positions);
 
 /**
- * Iterate through the hash table, returning key-value pairs.
+ * Initialize the iterator over the hash table.
  *
  * @param h
- *   Hash table to iterate
+ *   Hash table to iterate.
+ * @param state
+ *   Pointer to the iterator state.
+ * @return
+ *   - 0 if successful.
+ *   - -EINVAL if the parameters are invalid.
+ */
+int32_t
+rte_hash_iterator_init(const struct rte_hash *h,
+	struct rte_hash_iterator_state *state);
+
+/**
+ * Iterate through the hash table, returning key-value pairs.
+ *
+ * @param state
+ *   Pointer to the iterator state.
  * @param key
  *   Output containing the key where current iterator
  *   was pointing at
  * @param data
  *   Output containing the data associated with key.
  *   Returns NULL if data was not stored.
- * @param next
- *   Pointer to iterator. Should be 0 to start iterating the hash table.
- *   Iterator is incremented after each call of this function.
  * @return
  *   Position where key was stored, if successful.
  *   - -EINVAL if the parameters are invalid.
  *   - -ENOENT if end of the hash table.
  */
 int32_t
-rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32_t *next);
+rte_hash_iterate(
+	struct rte_hash_iterator_state *state, const void **key, void **data);
+
+/**
+ * Initialize the iterator over entries that conflict with a given hash.
+ *
+ * @param h
+ *   Hash table to iterate.
+ * @param sig
+ *   Precomputed hash value with which the returning entries conflict.
+ * @param state
+ *   Pointer to the iterator state.
+ * @return
+ *   - 0 if successful.
+ *   - -EINVAL if the parameters are invalid.
+ */
+int32_t __rte_experimental
+rte_hash_iterator_conflict_entries_init_with_hash(const struct rte_hash *h,
+	hash_sig_t sig, struct rte_hash_iterator_state *state);
+
+/**
+ * Iterate over entries that conflict with a given hash.
+ *
+ * @param state
+ *   Pointer to the iterator state.
+ * @param key
+ *   Output containing the key at where the iterator is currently pointing.
+ * @param data
+ *   Output containing the data associated with key.
+ *   Returns NULL if data was not stored.
+ * @return
+ *   Position where key was stored, if successful.
+ *   - -EINVAL if the parameters are invalid.
+ *   - -ENOENT if there is no more conflicting entries.
+ */
+int32_t __rte_experimental
+rte_hash_iterate_conflict_entries(
+	struct rte_hash_iterator_state *state, const void **key, void **data);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/librte_hash/rte_hash_version.map b/lib/librte_hash/rte_hash_version.map
index 52a2576f9..4ff175a73 100644
--- a/lib/librte_hash/rte_hash_version.map
+++ b/lib/librte_hash/rte_hash_version.map
@@ -24,6 +24,7 @@ DPDK_2.1 {
 
 	rte_hash_add_key_data;
 	rte_hash_add_key_with_hash_data;
+	rte_hash_iterator_init;
 	rte_hash_iterate;
 	rte_hash_lookup_bulk_data;
 	rte_hash_lookup_data;
@@ -45,3 +46,10 @@ DPDK_16.07 {
 	rte_hash_get_key_with_position;
 
 } DPDK_2.2;
+
+EXPERIMENTAL {
+	global:
+
+	rte_hash_iterator_conflict_entries_init_with_hash;
+	rte_hash_iterate_conflict_entries;
+};
diff --git a/test/test/test_hash.c b/test/test/test_hash.c
index edf41f5a7..3391f60ae 100644
--- a/test/test/test_hash.c
+++ b/test/test/test_hash.c
@@ -1158,8 +1158,8 @@ static int test_hash_iteration(void)
 	void *next_data;
 	void *data[NUM_ENTRIES];
 	unsigned added_keys;
-	uint32_t iter = 0;
 	int ret = 0;
+	struct rte_hash_iterator_state state;
 
 	ut_params.entries = NUM_ENTRIES;
 	ut_params.name = "test_hash_iteration";
@@ -1168,6 +1168,9 @@ static int test_hash_iteration(void)
 	handle = rte_hash_create(&ut_params);
 	RETURN_IF_ERROR(handle == NULL, "hash creation failed");
 
+	RETURN_IF_ERROR(rte_hash_iterator_init(handle, &state) != 0,
+			"initialization of the hash iterator failed");
+
 	/* Add random entries until key cannot be added */
 	for (added_keys = 0; added_keys < NUM_ENTRIES; added_keys++) {
 		data[added_keys] = (void *) ((uintptr_t) rte_rand());
@@ -1179,7 +1182,7 @@ static int test_hash_iteration(void)
 	}
 
 	/* Iterate through the hash table */
-	while (rte_hash_iterate(handle, &next_key, &next_data, &iter) >= 0) {
+	while (rte_hash_iterate(&state, &next_key, &next_data) >= 0) {
 		/* Search for the key in the list of keys added */
 		for (i = 0; i < NUM_ENTRIES; i++) {
 			if (memcmp(next_key, keys[i], ut_params.key_len) == 0) {
diff --git a/test/test/test_hash_multiwriter.c b/test/test/test_hash_multiwriter.c
index ef5fce3d2..ee0c615f4 100644
--- a/test/test/test_hash_multiwriter.c
+++ b/test/test/test_hash_multiwriter.c
@@ -112,17 +112,21 @@ test_hash_multiwriter(void)
 
 	const void *next_key;
 	void *next_data;
-	uint32_t iter = 0;
 
 	uint32_t duplicated_keys = 0;
 	uint32_t lost_keys = 0;
 
+	struct rte_hash_iterator_state state;
+
 	snprintf(name, 32, "test%u", calledCount++);
 	hash_params.name = name;
 
 	handle = rte_hash_create(&hash_params);
 	RETURN_IF_ERROR(handle == NULL, "hash creation failed");
 
+	RETURN_IF_ERROR(rte_hash_iterator_init(handle, &state) != 0,
+			"initialization of the hash iterator failed");
+
 	tbl_multiwriter_test_params.h = handle;
 	tbl_multiwriter_test_params.nb_tsx_insertion =
 		nb_total_tsx_insertion / rte_lcore_count();
@@ -163,7 +167,7 @@ test_hash_multiwriter(void)
 				 NULL, CALL_MASTER);
 	rte_eal_mp_wait_lcore();
 
-	while (rte_hash_iterate(handle, &next_key, &next_data, &iter) >= 0) {
+	while (rte_hash_iterate(&state, &next_key, &next_data) >= 0) {
 		/* Search for the key in the list of keys added .*/
 		i = *(const uint32_t *)next_key;
 		tbl_multiwriter_test_params.found[i]++;
-- 
2.17.1