New upstream version 18.11-rc1upstream/18.11-rc1

Change-Id: Iaa71986dd6332e878d8f4bf493101b2bbc6313bb
Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>

4 files changed, 903 insertions, 284 deletions

diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index f7b86c8c..5ddcccd8 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2010-2016 Intel Corporation
+ * Copyright(c) 2018 Arm Limited
  */
 
 #include <string.h>
@@ -26,11 +27,14 @@
 #include <rte_spinlock.h>
 #include <rte_ring.h>
 #include <rte_compat.h>
-#include <rte_pause.h>
 
 #include "rte_hash.h"
 #include "rte_cuckoo_hash.h"
 
+#define FOR_EACH_BUCKET(CURRENT_BKT, START_BUCKET)                            \
+	for (CURRENT_BKT = START_BUCKET;                                      \
+		CURRENT_BKT != NULL;                                          \
+		CURRENT_BKT = CURRENT_BKT->next)
 
 TAILQ_HEAD(rte_hash_list, rte_tailq_entry);
 
@@ -63,6 +67,14 @@ rte_hash_find_existing(const char *name)
 	return h;
 }
 
+static inline struct rte_hash_bucket *
+rte_hash_get_last_bkt(struct rte_hash_bucket *lst_bkt)
+{
+	while (lst_bkt->next != NULL)
+		lst_bkt = lst_bkt->next;
+	return lst_bkt;
+}
+
 void rte_hash_set_cmp_func(struct rte_hash *h, rte_hash_cmp_eq_t func)
 {
 	h->cmp_jump_table_idx = KEY_CUSTOM;
@@ -78,6 +90,36 @@ rte_hash_cmp_eq(const void *key1, const void *key2, const struct rte_hash *h)
 		return cmp_jump_table[h->cmp_jump_table_idx](key1, key2, h->key_len);
 }
 
+/*
+ * We use higher 16 bits of hash as the signature value stored in table.
+ * We use the lower bits for the primary bucket
+ * location. Then we XOR primary bucket location and the signature
+ * to get the secondary bucket location. This is same as
+ * proposed in Bin Fan, et al's paper
+ * "MemC3: Compact and Concurrent MemCache with Dumber Caching and
+ * Smarter Hashing". The benefit to use
+ * XOR is that one could derive the alternative bucket location
+ * by only using the current bucket location and the signature.
+ */
+static inline uint16_t
+get_short_sig(const hash_sig_t hash)
+{
+	return hash >> 16;
+}
+
+static inline uint32_t
+get_prim_bucket_index(const struct rte_hash *h, const hash_sig_t hash)
+{
+	return hash & h->bucket_bitmask;
+}
+
+static inline uint32_t
+get_alt_bucket_index(const struct rte_hash *h,
+			uint32_t cur_bkt_idx, uint16_t sig)
+{
+	return (cur_bkt_idx ^ sig) & h->bucket_bitmask;
+}
+
 struct rte_hash *
 rte_hash_create(const struct rte_hash_parameters *params)
 {
@@ -85,14 +127,22 @@ rte_hash_create(const struct rte_hash_parameters *params)
 	struct rte_tailq_entry *te = NULL;
 	struct rte_hash_list *hash_list;
 	struct rte_ring *r = NULL;
+	struct rte_ring *r_ext = NULL;
 	char hash_name[RTE_HASH_NAMESIZE];
 	void *k = NULL;
 	void *buckets = NULL;
+	void *buckets_ext = NULL;
 	char ring_name[RTE_RING_NAMESIZE];
+	char ext_ring_name[RTE_RING_NAMESIZE];
 	unsigned num_key_slots;
 	unsigned i;
-	unsigned int hw_trans_mem_support = 0, multi_writer_support = 0;
+	unsigned int hw_trans_mem_support = 0, use_local_cache = 0;
+	unsigned int ext_table_support = 0;
 	unsigned int readwrite_concur_support = 0;
+	unsigned int writer_takes_lock = 0;
+	unsigned int no_free_on_del = 0;
+	uint32_t *tbl_chng_cnt = NULL;
+	unsigned int readwrite_concur_lf_support = 0;
 
 	rte_hash_function default_hash_func = (rte_hash_function)rte_jhash;
 
@@ -112,20 +162,52 @@ rte_hash_create(const struct rte_hash_parameters *params)
 		return NULL;
 	}
 
+	/* Validate correct usage of extra options */
+	if ((params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY) &&
+	    (params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF)) {
+		rte_errno = EINVAL;
+		RTE_LOG(ERR, HASH, "rte_hash_create: choose rw concurrency or "
+			"rw concurrency lock free\n");
+		return NULL;
+	}
+
+	if ((params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF) &&
+	    (params->extra_flag & RTE_HASH_EXTRA_FLAGS_EXT_TABLE)) {
+		rte_errno = EINVAL;
+		RTE_LOG(ERR, HASH, "rte_hash_create: extendable bucket "
+			"feature not supported with rw concurrency "
+			"lock free\n");
+		return NULL;
+	}
+
 	/* Check extra flags field to check extra options. */
 	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_TRANS_MEM_SUPPORT)
 		hw_trans_mem_support = 1;
 
-	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD)
-		multi_writer_support = 1;
+	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD) {
+		use_local_cache = 1;
+		writer_takes_lock = 1;
+	}
 
 	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY) {
 		readwrite_concur_support = 1;
-		multi_writer_support = 1;
+		writer_takes_lock = 1;
+	}
+
+	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_EXT_TABLE)
+		ext_table_support = 1;
+
+	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL)
+		no_free_on_del = 1;
+
+	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF) {
+		readwrite_concur_lf_support = 1;
+		/* Enable not freeing internal memory/index on delete */
+		no_free_on_del = 1;
 	}
 
 	/* Store all keys and leave the first entry as a dummy entry for lookup_bulk */
-	if (multi_writer_support)
+	if (use_local_cache)
 		/*
 		 * Increase number of slots by total number of indices
 		 * that can be stored in the lcore caches
@@ -145,6 +227,24 @@ rte_hash_create(const struct rte_hash_parameters *params)
 		goto err;
 	}
 
+	const uint32_t num_buckets = rte_align32pow2(params->entries) /
+						RTE_HASH_BUCKET_ENTRIES;
+
+	/* Create ring for extendable buckets. */
+	if (ext_table_support) {
+		snprintf(ext_ring_name, sizeof(ext_ring_name), "HT_EXT_%s",
+								params->name);
+		r_ext = rte_ring_create(ext_ring_name,
+				rte_align32pow2(num_buckets + 1),
+				params->socket_id, 0);
+
+		if (r_ext == NULL) {
+			RTE_LOG(ERR, HASH, "ext buckets memory allocation "
+								"failed\n");
+			goto err;
+		}
+	}
+
 	snprintf(hash_name, sizeof(hash_name), "HT_%s", params->name);
 
 	rte_rwlock_write_lock(RTE_EAL_TAILQ_RWLOCK);
@@ -177,19 +277,37 @@ rte_hash_create(const struct rte_hash_parameters *params)
 		goto err_unlock;
 	}
 
-	const uint32_t num_buckets = rte_align32pow2(params->entries)
-					/ RTE_HASH_BUCKET_ENTRIES;
-
 	buckets = rte_zmalloc_socket(NULL,
 				num_buckets * sizeof(struct rte_hash_bucket),
 				RTE_CACHE_LINE_SIZE, params->socket_id);
 
 	if (buckets == NULL) {
-		RTE_LOG(ERR, HASH, "memory allocation failed\n");
+		RTE_LOG(ERR, HASH, "buckets memory allocation failed\n");
 		goto err_unlock;
 	}
 
-	const uint32_t key_entry_size = sizeof(struct rte_hash_key) + params->key_len;
+	/* Allocate same number of extendable buckets */
+	if (ext_table_support) {
+		buckets_ext = rte_zmalloc_socket(NULL,
+				num_buckets * sizeof(struct rte_hash_bucket),
+				RTE_CACHE_LINE_SIZE, params->socket_id);
+		if (buckets_ext == NULL) {
+			RTE_LOG(ERR, HASH, "ext buckets memory allocation "
+							"failed\n");
+			goto err_unlock;
+		}
+		/* Populate ext bkt ring. We reserve 0 similar to the
+		 * key-data slot, just in case in future we want to
+		 * use bucket index for the linked list and 0 means NULL
+		 * for next bucket
+		 */
+		for (i = 1; i <= num_buckets; i++)
+			rte_ring_sp_enqueue(r_ext, (void *)((uintptr_t) i));
+	}
+
+	const uint32_t key_entry_size =
+		RTE_ALIGN(sizeof(struct rte_hash_key) + params->key_len,
+			  KEY_ALIGNMENT);
 	const uint64_t key_tbl_size = (uint64_t) key_entry_size * num_key_slots;
 
 	k = rte_zmalloc_socket(NULL, key_tbl_size,
@@ -200,6 +318,14 @@ rte_hash_create(const struct rte_hash_parameters *params)
 		goto err_unlock;
 	}
 
+	tbl_chng_cnt = rte_zmalloc_socket(NULL, sizeof(uint32_t),
+			RTE_CACHE_LINE_SIZE, params->socket_id);
+
+	if (tbl_chng_cnt == NULL) {
+		RTE_LOG(ERR, HASH, "memory allocation failed\n");
+		goto err_unlock;
+	}
+
 /*
  * If x86 architecture is used, select appropriate compare function,
  * which may use x86 intrinsics, otherwise use memcmp
@@ -239,7 +365,7 @@ rte_hash_create(const struct rte_hash_parameters *params)
 	h->cmp_jump_table_idx = KEY_OTHER_BYTES;
 #endif
 
-	if (multi_writer_support) {
+	if (use_local_cache) {
 		h->local_free_slots = rte_zmalloc_socket(NULL,
 				sizeof(struct lcore_cache) * RTE_MAX_LCORE,
 				RTE_CACHE_LINE_SIZE, params->socket_id);
@@ -262,27 +388,34 @@ rte_hash_create(const struct rte_hash_parameters *params)
 	h->num_buckets = num_buckets;
 	h->bucket_bitmask = h->num_buckets - 1;
 	h->buckets = buckets;
+	h->buckets_ext = buckets_ext;
+	h->free_ext_bkts = r_ext;
 	h->hash_func = (params->hash_func == NULL) ?
 		default_hash_func : params->hash_func;
 	h->key_store = k;
 	h->free_slots = r;
+	h->tbl_chng_cnt = tbl_chng_cnt;
+	*h->tbl_chng_cnt = 0;
 	h->hw_trans_mem_support = hw_trans_mem_support;
-	h->multi_writer_support = multi_writer_support;
+	h->use_local_cache = use_local_cache;
 	h->readwrite_concur_support = readwrite_concur_support;
+	h->ext_table_support = ext_table_support;
+	h->writer_takes_lock = writer_takes_lock;
+	h->no_free_on_del = no_free_on_del;
+	h->readwrite_concur_lf_support = readwrite_concur_lf_support;
 
 #if defined(RTE_ARCH_X86)
-	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2))
-		h->sig_cmp_fn = RTE_HASH_COMPARE_AVX2;
-	else if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE2))
+	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE2))
 		h->sig_cmp_fn = RTE_HASH_COMPARE_SSE;
 	else
 #endif
 		h->sig_cmp_fn = RTE_HASH_COMPARE_SCALAR;
 
-	/* Turn on multi-writer only with explicit flag from user and TM
-	 * support.
+	/* Writer threads need to take the lock when:
+	 * 1) RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY is enabled OR
+	 * 2) RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD is enabled
 	 */
-	if (h->multi_writer_support) {
+	if (h->writer_takes_lock) {
 		h->readwrite_lock = rte_malloc(NULL, sizeof(rte_rwlock_t),
 						RTE_CACHE_LINE_SIZE);
 		if (h->readwrite_lock == NULL)
@@ -304,10 +437,13 @@ err_unlock:
 	rte_rwlock_write_unlock(RTE_EAL_TAILQ_RWLOCK);
 err:
 	rte_ring_free(r);
+	rte_ring_free(r_ext);
 	rte_free(te);
 	rte_free(h);
 	rte_free(buckets);
+	rte_free(buckets_ext);
 	rte_free(k);
+	rte_free(tbl_chng_cnt);
 	return NULL;
 }
 
@@ -339,13 +475,16 @@ rte_hash_free(struct rte_hash *h)
 
 	rte_rwlock_write_unlock(RTE_EAL_TAILQ_RWLOCK);
 
-	if (h->multi_writer_support) {
+	if (h->use_local_cache)
 		rte_free(h->local_free_slots);
+	if (h->writer_takes_lock)
 		rte_free(h->readwrite_lock);
-	}
 	rte_ring_free(h->free_slots);
+	rte_ring_free(h->free_ext_bkts);
 	rte_free(h->key_store);
 	rte_free(h->buckets);
+	rte_free(h->buckets_ext);
+	rte_free(h->tbl_chng_cnt);
 	rte_free(h);
 	rte_free(te);
 }
@@ -357,18 +496,6 @@ rte_hash_hash(const struct rte_hash *h, const void *key)
 	return h->hash_func(key, h->key_len, h->hash_func_init_val);
 }
 
-/* Calc the secondary hash value from the primary hash value of a given key */
-static inline hash_sig_t
-rte_hash_secondary_hash(const hash_sig_t primary_hash)
-{
-	static const unsigned all_bits_shift = 12;
-	static const unsigned alt_bits_xor = 0x5bd1e995;
-
-	uint32_t tag = primary_hash >> all_bits_shift;
-
-	return primary_hash ^ ((tag + 1) * alt_bits_xor);
-}
-
 int32_t
 rte_hash_count(const struct rte_hash *h)
 {
@@ -378,7 +505,7 @@ rte_hash_count(const struct rte_hash *h)
 	if (h == NULL)
 		return -EINVAL;
 
-	if (h->multi_writer_support) {
+	if (h->use_local_cache) {
 		tot_ring_cnt = h->entries + (RTE_MAX_LCORE - 1) *
 					(LCORE_CACHE_SIZE - 1);
 		for (i = 0; i < RTE_MAX_LCORE; i++)
@@ -397,13 +524,12 @@ rte_hash_count(const struct rte_hash *h)
 static inline void
 __hash_rw_writer_lock(const struct rte_hash *h)
 {
-	if (h->multi_writer_support && h->hw_trans_mem_support)
+	if (h->writer_takes_lock && h->hw_trans_mem_support)
 		rte_rwlock_write_lock_tm(h->readwrite_lock);
-	else if (h->multi_writer_support)
+	else if (h->writer_takes_lock)
 		rte_rwlock_write_lock(h->readwrite_lock);
 }
 
-
 static inline void
 __hash_rw_reader_lock(const struct rte_hash *h)
 {
@@ -416,9 +542,9 @@ __hash_rw_reader_lock(const struct rte_hash *h)
 static inline void
 __hash_rw_writer_unlock(const struct rte_hash *h)
 {
-	if (h->multi_writer_support && h->hw_trans_mem_support)
+	if (h->writer_takes_lock && h->hw_trans_mem_support)
 		rte_rwlock_write_unlock_tm(h->readwrite_lock);
-	else if (h->multi_writer_support)
+	else if (h->writer_takes_lock)
 		rte_rwlock_write_unlock(h->readwrite_lock);
 }
 
@@ -443,13 +569,22 @@ rte_hash_reset(struct rte_hash *h)
 	__hash_rw_writer_lock(h);
 	memset(h->buckets, 0, h->num_buckets * sizeof(struct rte_hash_bucket));
 	memset(h->key_store, 0, h->key_entry_size * (h->entries + 1));
+	*h->tbl_chng_cnt = 0;
 
 	/* clear the free ring */
 	while (rte_ring_dequeue(h->free_slots, &ptr) == 0)
-		rte_pause();
+		continue;
+
+	/* clear free extendable bucket ring and memory */
+	if (h->ext_table_support) {
+		memset(h->buckets_ext, 0, h->num_buckets *
+						sizeof(struct rte_hash_bucket));
+		while (rte_ring_dequeue(h->free_ext_bkts, &ptr) == 0)
+			continue;
+	}
 
 	/* Repopulate the free slots ring. Entry zero is reserved for key misses */
-	if (h->multi_writer_support)
+	if (h->use_local_cache)
 		tot_ring_cnt = h->entries + (RTE_MAX_LCORE - 1) *
 					(LCORE_CACHE_SIZE - 1);
 	else
@@ -458,7 +593,14 @@ rte_hash_reset(struct rte_hash *h)
 	for (i = 1; i < tot_ring_cnt + 1; i++)
 		rte_ring_sp_enqueue(h->free_slots, (void *)((uintptr_t) i));
 
-	if (h->multi_writer_support) {
+	/* Repopulate the free ext bkt ring. */
+	if (h->ext_table_support) {
+		for (i = 1; i <= h->num_buckets; i++)
+			rte_ring_sp_enqueue(h->free_ext_bkts,
+						(void *)((uintptr_t) i));
+	}
+
+	if (h->use_local_cache) {
 		/* Reset local caches per lcore */
 		for (i = 0; i < RTE_MAX_LCORE; i++)
 			h->local_free_slots[i].len = 0;
@@ -476,29 +618,35 @@ enqueue_slot_back(const struct rte_hash *h,
 		struct lcore_cache *cached_free_slots,
 		void *slot_id)
 {
-	if (h->multi_writer_support) {
+	if (h->use_local_cache) {
 		cached_free_slots->objs[cached_free_slots->len] = slot_id;
 		cached_free_slots->len++;
 	} else
 		rte_ring_sp_enqueue(h->free_slots, slot_id);
 }
 
-/* Search a key from bucket and update its data */
+/* Search a key from bucket and update its data.
+ * Writer holds the lock before calling this.
+ */
 static inline int32_t
 search_and_update(const struct rte_hash *h, void *data, const void *key,
-	struct rte_hash_bucket *bkt, hash_sig_t sig, hash_sig_t alt_hash)
+	struct rte_hash_bucket *bkt, uint16_t sig)
 {
 	int i;
 	struct rte_hash_key *k, *keys = h->key_store;
 
 	for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
-		if (bkt->sig_current[i] == sig &&
-				bkt->sig_alt[i] == alt_hash) {
+		if (bkt->sig_current[i] == sig) {
 			k = (struct rte_hash_key *) ((char *)keys +
 					bkt->key_idx[i] * h->key_entry_size);
 			if (rte_hash_cmp_eq(key, k->key, h) == 0) {
-				/* Update data */
-				k->pdata = data;
+				/* 'pdata' acts as the synchronization point
+				 * when an existing hash entry is updated.
+				 * Key is not updated in this case.
+				 */
+				__atomic_store_n(&k->pdata,
+					data,
+					__ATOMIC_RELEASE);
 				/*
 				 * Return index where key is stored,
 				 * subtracting the first dummy index
@@ -520,28 +668,31 @@ rte_hash_cuckoo_insert_mw(const struct rte_hash *h,
 		struct rte_hash_bucket *prim_bkt,
 		struct rte_hash_bucket *sec_bkt,
 		const struct rte_hash_key *key, void *data,
-		hash_sig_t sig, hash_sig_t alt_hash, uint32_t new_idx,
+		uint16_t sig, uint32_t new_idx,
 		int32_t *ret_val)
 {
 	unsigned int i;
-	struct rte_hash_bucket *cur_bkt = prim_bkt;
+	struct rte_hash_bucket *cur_bkt;
 	int32_t ret;
 
 	__hash_rw_writer_lock(h);
 	/* Check if key was inserted after last check but before this
 	 * protected region in case of inserting duplicated keys.
 	 */
-	ret = search_and_update(h, data, key, cur_bkt, sig, alt_hash);
+	ret = search_and_update(h, data, key, prim_bkt, sig);
 	if (ret != -1) {
 		__hash_rw_writer_unlock(h);
 		*ret_val = ret;
 		return 1;
 	}
-	ret = search_and_update(h, data, key, sec_bkt, alt_hash, sig);
-	if (ret != -1) {
-		__hash_rw_writer_unlock(h);
-		*ret_val = ret;
-		return 1;
+
+	FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
+		ret = search_and_update(h, data, key, cur_bkt, sig);
+		if (ret != -1) {
+			__hash_rw_writer_unlock(h);
+			*ret_val = ret;
+			return 1;
+		}
 	}
 
 	/* Insert new entry if there is room in the primary
@@ -551,8 +702,15 @@ rte_hash_cuckoo_insert_mw(const struct rte_hash *h,
 		/* Check if slot is available */
 		if (likely(prim_bkt->key_idx[i] == EMPTY_SLOT)) {
 			prim_bkt->sig_current[i] = sig;
-			prim_bkt->sig_alt[i] = alt_hash;
-			prim_bkt->key_idx[i] = new_idx;
+			/* Key can be of arbitrary length, so it is
+			 * not possible to store it atomically.
+			 * Hence the new key element's memory stores
+			 * (key as well as data) should be complete
+			 * before it is referenced.
+			 */
+			__atomic_store_n(&prim_bkt->key_idx[i],
+					 new_idx,
+					 __ATOMIC_RELEASE);
 			break;
 		}
 	}
@@ -576,11 +734,11 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h,
 			struct rte_hash_bucket *alt_bkt,
 			const struct rte_hash_key *key, void *data,
 			struct queue_node *leaf, uint32_t leaf_slot,
-			hash_sig_t sig, hash_sig_t alt_hash, uint32_t new_idx,
+			uint16_t sig, uint32_t new_idx,
 			int32_t *ret_val)
 {
 	uint32_t prev_alt_bkt_idx;
-	struct rte_hash_bucket *cur_bkt = bkt;
+	struct rte_hash_bucket *cur_bkt;
 	struct queue_node *prev_node, *curr_node = leaf;
 	struct rte_hash_bucket *prev_bkt, *curr_bkt = leaf->bkt;
 	uint32_t prev_slot, curr_slot = leaf_slot;
@@ -597,18 +755,20 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h,
 	/* Check if key was inserted after last check but before this
 	 * protected region.
 	 */
-	ret = search_and_update(h, data, key, cur_bkt, sig, alt_hash);
+	ret = search_and_update(h, data, key, bkt, sig);
 	if (ret != -1) {
 		__hash_rw_writer_unlock(h);
 		*ret_val = ret;
 		return 1;
 	}
 
-	ret = search_and_update(h, data, key, alt_bkt, alt_hash, sig);
-	if (ret != -1) {
-		__hash_rw_writer_unlock(h);
-		*ret_val = ret;
-		return 1;
+	FOR_EACH_BUCKET(cur_bkt, alt_bkt) {
+		ret = search_and_update(h, data, key, cur_bkt, sig);
+		if (ret != -1) {
+			__hash_rw_writer_unlock(h);
+			*ret_val = ret;
+			return 1;
+		}
 	}
 
 	while (likely(curr_node->prev != NULL)) {
@@ -616,36 +776,73 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h,
 		prev_bkt = prev_node->bkt;
 		prev_slot = curr_node->prev_slot;
 
-		prev_alt_bkt_idx =
-			prev_bkt->sig_alt[prev_slot] & h->bucket_bitmask;
+		prev_alt_bkt_idx = get_alt_bucket_index(h,
+					prev_node->cur_bkt_idx,
+					prev_bkt->sig_current[prev_slot]);
 
 		if (unlikely(&h->buckets[prev_alt_bkt_idx]
 				!= curr_bkt)) {
 			/* revert it to empty, otherwise duplicated keys */
-			curr_bkt->key_idx[curr_slot] = EMPTY_SLOT;
+			__atomic_store_n(&curr_bkt->key_idx[curr_slot],
+				EMPTY_SLOT,
+				__ATOMIC_RELEASE);
 			__hash_rw_writer_unlock(h);
 			return -1;
 		}
 
+		if (h->readwrite_concur_lf_support) {
+			/* Inform the previous move. The current move need
+			 * not be informed now as the current bucket entry
+			 * is present in both primary and secondary.
+			 * Since there is one writer, load acquires on
+			 * tbl_chng_cnt are not required.
+			 */
+			__atomic_store_n(h->tbl_chng_cnt,
+					 *h->tbl_chng_cnt + 1,
+					 __ATOMIC_RELEASE);
+			/* The stores to sig_alt and sig_current should not
+			 * move above the store to tbl_chng_cnt.
+			 */
+			__atomic_thread_fence(__ATOMIC_RELEASE);
+		}
+
 		/* Need to swap current/alt sig to allow later
 		 * Cuckoo insert to move elements back to its
 		 * primary bucket if available
 		 */
-		curr_bkt->sig_alt[curr_slot] =
-			 prev_bkt->sig_current[prev_slot];
 		curr_bkt->sig_current[curr_slot] =
-			prev_bkt->sig_alt[prev_slot];
-		curr_bkt->key_idx[curr_slot] =
-			prev_bkt->key_idx[prev_slot];
+			prev_bkt->sig_current[prev_slot];
+		/* Release the updated bucket entry */
+		__atomic_store_n(&curr_bkt->key_idx[curr_slot],
+			prev_bkt->key_idx[prev_slot],
+			__ATOMIC_RELEASE);
 
 		curr_slot = prev_slot;
 		curr_node = prev_node;
 		curr_bkt = curr_node->bkt;
 	}
 
+	if (h->readwrite_concur_lf_support) {
+		/* Inform the previous move. The current move need
+		 * not be informed now as the current bucket entry
+		 * is present in both primary and secondary.
+		 * Since there is one writer, load acquires on
+		 * tbl_chng_cnt are not required.
+		 */
+		__atomic_store_n(h->tbl_chng_cnt,
+				 *h->tbl_chng_cnt + 1,
+				 __ATOMIC_RELEASE);
+		/* The stores to sig_alt and sig_current should not
+		 * move above the store to tbl_chng_cnt.
+		 */
+		__atomic_thread_fence(__ATOMIC_RELEASE);
+	}
+
 	curr_bkt->sig_current[curr_slot] = sig;
-	curr_bkt->sig_alt[curr_slot] = alt_hash;
-	curr_bkt->key_idx[curr_slot] = new_idx;
+	/* Release the new bucket entry */
+	__atomic_store_n(&curr_bkt->key_idx[curr_slot],
+			 new_idx,
+			 __ATOMIC_RELEASE);
 
 	__hash_rw_writer_unlock(h);
 
@@ -662,39 +859,44 @@ rte_hash_cuckoo_make_space_mw(const struct rte_hash *h,
 			struct rte_hash_bucket *bkt,
 			struct rte_hash_bucket *sec_bkt,
 			const struct rte_hash_key *key, void *data,
-			hash_sig_t sig, hash_sig_t alt_hash,
+			uint16_t sig, uint32_t bucket_idx,
 			uint32_t new_idx, int32_t *ret_val)
 {
 	unsigned int i;
 	struct queue_node queue[RTE_HASH_BFS_QUEUE_MAX_LEN];
 	struct queue_node *tail, *head;
 	struct rte_hash_bucket *curr_bkt, *alt_bkt;
+	uint32_t cur_idx, alt_idx;
 
 	tail = queue;
 	head = queue + 1;
 	tail->bkt = bkt;
 	tail->prev = NULL;
 	tail->prev_slot = -1;
+	tail->cur_bkt_idx = bucket_idx;
 
 	/* Cuckoo bfs Search */
 	while (likely(tail != head && head <
 					queue + RTE_HASH_BFS_QUEUE_MAX_LEN -
 					RTE_HASH_BUCKET_ENTRIES)) {
 		curr_bkt = tail->bkt;
+		cur_idx = tail->cur_bkt_idx;
 		for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
 			if (curr_bkt->key_idx[i] == EMPTY_SLOT) {
 				int32_t ret = rte_hash_cuckoo_move_insert_mw(h,
 						bkt, sec_bkt, key, data,
-						tail, i, sig, alt_hash,
+						tail, i, sig,
 						new_idx, ret_val);
 				if (likely(ret != -1))
 					return ret;
 			}
 
 			/* Enqueue new node and keep prev node info */
-			alt_bkt = &(h->buckets[curr_bkt->sig_alt[i]
-						    & h->bucket_bitmask]);
+			alt_idx = get_alt_bucket_index(h, cur_idx,
+						curr_bkt->sig_current[i]);
+			alt_bkt = &(h->buckets[alt_idx]);
 			head->bkt = alt_bkt;
+			head->cur_bkt_idx = alt_idx;
 			head->prev = tail;
 			head->prev_slot = i;
 			head++;
@@ -709,45 +911,50 @@ static inline int32_t
 __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
 						hash_sig_t sig, void *data)
 {
-	hash_sig_t alt_hash;
+	uint16_t short_sig;
 	uint32_t prim_bucket_idx, sec_bucket_idx;
-	struct rte_hash_bucket *prim_bkt, *sec_bkt;
+	struct rte_hash_bucket *prim_bkt, *sec_bkt, *cur_bkt;
 	struct rte_hash_key *new_k, *keys = h->key_store;
 	void *slot_id = NULL;
-	uint32_t new_idx;
+	void *ext_bkt_id = NULL;
+	uint32_t new_idx, bkt_id;
 	int ret;
 	unsigned n_slots;
 	unsigned lcore_id;
+	unsigned int i;
 	struct lcore_cache *cached_free_slots = NULL;
 	int32_t ret_val;
+	struct rte_hash_bucket *last;
 
-	prim_bucket_idx = sig & h->bucket_bitmask;
+	short_sig = get_short_sig(sig);
+	prim_bucket_idx = get_prim_bucket_index(h, sig);
+	sec_bucket_idx = get_alt_bucket_index(h, prim_bucket_idx, short_sig);
 	prim_bkt = &h->buckets[prim_bucket_idx];
-	rte_prefetch0(prim_bkt);
-
-	alt_hash = rte_hash_secondary_hash(sig);
-	sec_bucket_idx = alt_hash & h->bucket_bitmask;
 	sec_bkt = &h->buckets[sec_bucket_idx];
+	rte_prefetch0(prim_bkt);
 	rte_prefetch0(sec_bkt);
 
 	/* Check if key is already inserted in primary location */
 	__hash_rw_writer_lock(h);
-	ret = search_and_update(h, data, key, prim_bkt, sig, alt_hash);
+	ret = search_and_update(h, data, key, prim_bkt, short_sig);
 	if (ret != -1) {
 		__hash_rw_writer_unlock(h);
 		return ret;
 	}
 
 	/* Check if key is already inserted in secondary location */
-	ret = search_and_update(h, data, key, sec_bkt, alt_hash, sig);
-	if (ret != -1) {
-		__hash_rw_writer_unlock(h);
-		return ret;
+	FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
+		ret = search_and_update(h, data, key, cur_bkt, short_sig);
+		if (ret != -1) {
+			__hash_rw_writer_unlock(h);
+			return ret;
+		}
 	}
+
 	__hash_rw_writer_unlock(h);
 
 	/* Did not find a match, so get a new slot for storing the new key */
-	if (h->multi_writer_support) {
+	if (h->use_local_cache) {
 		lcore_id = rte_lcore_id();
 		cached_free_slots = &h->local_free_slots[lcore_id];
 		/* Try to get a free slot from the local cache */
@@ -776,12 +983,19 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
 	new_idx = (uint32_t)((uintptr_t) slot_id);
 	/* Copy key */
 	rte_memcpy(new_k->key, key, h->key_len);
-	new_k->pdata = data;
-
+	/* Key can be of arbitrary length, so it is not possible to store
+	 * it atomically. Hence the new key element's memory stores
+	 * (key as well as data) should be complete before it is referenced.
+	 * 'pdata' acts as the synchronization point when an existing hash
+	 * entry is updated.
+	 */
+	__atomic_store_n(&new_k->pdata,
+		data,
+		__ATOMIC_RELEASE);
 
 	/* Find an empty slot and insert */
 	ret = rte_hash_cuckoo_insert_mw(h, prim_bkt, sec_bkt, key, data,
-					sig, alt_hash, new_idx, &ret_val);
+					short_sig, new_idx, &ret_val);
 	if (ret == 0)
 		return new_idx - 1;
 	else if (ret == 1) {
@@ -791,7 +1005,7 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
 
 	/* Primary bucket full, need to make space for new entry */
 	ret = rte_hash_cuckoo_make_space_mw(h, prim_bkt, sec_bkt, key, data,
-					sig, alt_hash, new_idx, &ret_val);
+				short_sig, prim_bucket_idx, new_idx, &ret_val);
 	if (ret == 0)
 		return new_idx - 1;
 	else if (ret == 1) {
@@ -801,17 +1015,75 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
 
 	/* Also search secondary bucket to get better occupancy */
 	ret = rte_hash_cuckoo_make_space_mw(h, sec_bkt, prim_bkt, key, data,
-					alt_hash, sig, new_idx, &ret_val);
+				short_sig, sec_bucket_idx, new_idx, &ret_val);
 
 	if (ret == 0)
 		return new_idx - 1;
 	else if (ret == 1) {
 		enqueue_slot_back(h, cached_free_slots, slot_id);
 		return ret_val;
-	} else {
+	}
+
+	/* if ext table not enabled, we failed the insertion */
+	if (!h->ext_table_support) {
 		enqueue_slot_back(h, cached_free_slots, slot_id);
 		return ret;
 	}
+
+	/* Now we need to go through the extendable bucket. Protection is needed
+	 * to protect all extendable bucket processes.
+	 */
+	__hash_rw_writer_lock(h);
+	/* We check for duplicates again since could be inserted before the lock */
+	ret = search_and_update(h, data, key, prim_bkt, short_sig);
+	if (ret != -1) {
+		enqueue_slot_back(h, cached_free_slots, slot_id);
+		goto failure;
+	}
+
+	FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
+		ret = search_and_update(h, data, key, cur_bkt, short_sig);
+		if (ret != -1) {
+			enqueue_slot_back(h, cached_free_slots, slot_id);
+			goto failure;
+		}
+	}
+
+	/* Search sec and ext buckets to find an empty entry to insert. */
+	FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
+		for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
+			/* Check if slot is available */
+			if (likely(cur_bkt->key_idx[i] == EMPTY_SLOT)) {
+				cur_bkt->sig_current[i] = short_sig;
+				cur_bkt->key_idx[i] = new_idx;
+				__hash_rw_writer_unlock(h);
+				return new_idx - 1;
+			}
+		}
+	}
+
+	/* Failed to get an empty entry from extendable buckets. Link a new
+	 * extendable bucket. We first get a free bucket from ring.
+	 */
+	if (rte_ring_sc_dequeue(h->free_ext_bkts, &ext_bkt_id) != 0) {
+		ret = -ENOSPC;
+		goto failure;
+	}
+
+	bkt_id = (uint32_t)((uintptr_t)ext_bkt_id) - 1;
+	/* Use the first location of the new bucket */
+	(h->buckets_ext[bkt_id]).sig_current[0] = short_sig;
+	(h->buckets_ext[bkt_id]).key_idx[0] = new_idx;
+	/* Link the new bucket to sec bucket linked list */
+	last = rte_hash_get_last_bkt(sec_bkt);
+	last->next = &h->buckets_ext[bkt_id];
+	__hash_rw_writer_unlock(h);
+	return new_idx - 1;
+
+failure:
+	__hash_rw_writer_unlock(h);
+	return ret;
+
 }
 
 int32_t
@@ -859,25 +1131,31 @@ rte_hash_add_key_data(const struct rte_hash *h, const void *key, void *data)
 
 /* Search one bucket to find the match key */
 static inline int32_t
-search_one_bucket(const struct rte_hash *h, const void *key, hash_sig_t sig,
+search_one_bucket(const struct rte_hash *h, const void *key, uint16_t sig,
 			void **data, const struct rte_hash_bucket *bkt)
 {
 	int i;
+	uint32_t key_idx;
+	void *pdata;
 	struct rte_hash_key *k, *keys = h->key_store;
 
 	for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
-		if (bkt->sig_current[i] == sig &&
-				bkt->key_idx[i] != EMPTY_SLOT) {
+		key_idx = __atomic_load_n(&bkt->key_idx[i],
+					  __ATOMIC_ACQUIRE);
+		if (bkt->sig_current[i] == sig && key_idx != EMPTY_SLOT) {
 			k = (struct rte_hash_key *) ((char *)keys +
-					bkt->key_idx[i] * h->key_entry_size);
+					key_idx * h->key_entry_size);
+			pdata = __atomic_load_n(&k->pdata,
+					__ATOMIC_ACQUIRE);
+
 			if (rte_hash_cmp_eq(key, k->key, h) == 0) {
 				if (data != NULL)
-					*data = k->pdata;
+					*data = pdata;
 				/*
 				 * Return index where key is stored,
 				 * subtracting the first dummy index
 				 */
-				return bkt->key_idx[i] - 1;
+				return key_idx - 1;
 			}
 		}
 	}
@@ -888,34 +1166,64 @@ static inline int32_t
 __rte_hash_lookup_with_hash(const struct rte_hash *h, const void *key,
 					hash_sig_t sig, void **data)
 {
-	uint32_t bucket_idx;
-	hash_sig_t alt_hash;
-	struct rte_hash_bucket *bkt;
+	uint32_t prim_bucket_idx, sec_bucket_idx;
+	struct rte_hash_bucket *bkt, *cur_bkt;
+	uint32_t cnt_b, cnt_a;
 	int ret;
+	uint16_t short_sig;
 
-	bucket_idx = sig & h->bucket_bitmask;
-	bkt = &h->buckets[bucket_idx];
+	short_sig = get_short_sig(sig);
+	prim_bucket_idx = get_prim_bucket_index(h, sig);
+	sec_bucket_idx = get_alt_bucket_index(h, prim_bucket_idx, short_sig);
 
 	__hash_rw_reader_lock(h);
 
-	/* Check if key is in primary location */
-	ret = search_one_bucket(h, key, sig, data, bkt);
-	if (ret != -1) {
-		__hash_rw_reader_unlock(h);
-		return ret;
-	}
-	/* Calculate secondary hash */
-	alt_hash = rte_hash_secondary_hash(sig);
-	bucket_idx = alt_hash & h->bucket_bitmask;
-	bkt = &h->buckets[bucket_idx];
+	do {
+		/* Load the table change counter before the lookup
+		 * starts. Acquire semantics will make sure that
+		 * loads in search_one_bucket are not hoisted.
+		 */
+		cnt_b = __atomic_load_n(h->tbl_chng_cnt,
+				__ATOMIC_ACQUIRE);
+
+		/* Check if key is in primary location */
+		bkt = &h->buckets[prim_bucket_idx];
+		ret = search_one_bucket(h, key, short_sig, data, bkt);
+		if (ret != -1) {
+			__hash_rw_reader_unlock(h);
+			return ret;
+		}
+		/* Calculate secondary hash */
+		bkt = &h->buckets[sec_bucket_idx];
+
+		/* Check if key is in secondary location */
+		FOR_EACH_BUCKET(cur_bkt, bkt) {
+			ret = search_one_bucket(h, key, short_sig,
+						data, cur_bkt);
+			if (ret != -1) {
+				__hash_rw_reader_unlock(h);
+				return ret;
+			}
+		}
+
+		/* The loads of sig_current in search_one_bucket
+		 * should not move below the load from tbl_chng_cnt.
+		 */
+		__atomic_thread_fence(__ATOMIC_ACQUIRE);
+		/* Re-read the table change counter to check if the
+		 * table has changed during search. If yes, re-do
+		 * the search.
+		 * This load should not get hoisted. The load
+		 * acquires on cnt_b, key index in primary bucket
+		 * and key index in secondary bucket will make sure
+		 * that it does not get hoisted.
+		 */
+		cnt_a = __atomic_load_n(h->tbl_chng_cnt,
+					__ATOMIC_ACQUIRE);
+	} while (cnt_b != cnt_a);
 
-	/* Check if key is in secondary location */
-	ret = search_one_bucket(h, key, alt_hash, data, bkt);
-	if (ret != -1) {
-		__hash_rw_reader_unlock(h);
-		return ret;
-	}
 	__hash_rw_reader_unlock(h);
+
 	return -ENOENT;
 }
 
@@ -955,9 +1263,7 @@ remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
 	unsigned lcore_id, n_slots;
 	struct lcore_cache *cached_free_slots;
 
-	bkt->sig_current[i] = NULL_SIGNATURE;
-	bkt->sig_alt[i] = NULL_SIGNATURE;
-	if (h->multi_writer_support) {
+	if (h->use_local_cache) {
 		lcore_id = rte_lcore_id();
 		cached_free_slots = &h->local_free_slots[lcore_id];
 		/* Cache full, need to free it. */
@@ -978,31 +1284,67 @@ remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
 	}
 }
 
-/* Search one bucket and remove the matched key */
+/* Compact the linked list by moving key from last entry in linked list to the
+ * empty slot.
+ */
+static inline void
+__rte_hash_compact_ll(struct rte_hash_bucket *cur_bkt, int pos) {
+	int i;
+	struct rte_hash_bucket *last_bkt;
+
+	if (!cur_bkt->next)
+		return;
+
+	last_bkt = rte_hash_get_last_bkt(cur_bkt);
+
+	for (i = RTE_HASH_BUCKET_ENTRIES - 1; i >= 0; i--) {
+		if (last_bkt->key_idx[i] != EMPTY_SLOT) {
+			cur_bkt->key_idx[pos] = last_bkt->key_idx[i];
+			cur_bkt->sig_current[pos] = last_bkt->sig_current[i];
+			last_bkt->sig_current[i] = NULL_SIGNATURE;
+			last_bkt->key_idx[i] = EMPTY_SLOT;
+			return;
+		}
+	}
+}
+
+/* Search one bucket and remove the matched key.
+ * Writer is expected to hold the lock while calling this
+ * function.
+ */
 static inline int32_t
 search_and_remove(const struct rte_hash *h, const void *key,
-			struct rte_hash_bucket *bkt, hash_sig_t sig)
+			struct rte_hash_bucket *bkt, uint16_t sig, int *pos)
 {
 	struct rte_hash_key *k, *keys = h->key_store;
 	unsigned int i;
-	int32_t ret;
+	uint32_t key_idx;
 
-	/* Check if key is in primary location */
+	/* Check if key is in bucket */
 	for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
-		if (bkt->sig_current[i] == sig &&
-				bkt->key_idx[i] != EMPTY_SLOT) {
+		key_idx = __atomic_load_n(&bkt->key_idx[i],
+					  __ATOMIC_ACQUIRE);
+		if (bkt->sig_current[i] == sig && key_idx != EMPTY_SLOT) {
 			k = (struct rte_hash_key *) ((char *)keys +
-					bkt->key_idx[i] * h->key_entry_size);
+					key_idx * h->key_entry_size);
 			if (rte_hash_cmp_eq(key, k->key, h) == 0) {
-				remove_entry(h, bkt, i);
+				bkt->sig_current[i] = NULL_SIGNATURE;
+				/* Free the key store index if
+				 * no_free_on_del is disabled.
+				 */
+				if (!h->no_free_on_del)
+					remove_entry(h, bkt, i);
+
+				__atomic_store_n(&bkt->key_idx[i],
+						 EMPTY_SLOT,
+						 __ATOMIC_RELEASE);
 
+				*pos = i;
 				/*
 				 * Return index where key is stored,
 				 * subtracting the first dummy index
 				 */
-				ret = bkt->key_idx[i] - 1;
-				bkt->key_idx[i] = EMPTY_SLOT;
-				return ret;
+				return key_idx - 1;
 			}
 		}
 	}
@@ -1013,36 +1355,68 @@ static inline int32_t
 __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
 						hash_sig_t sig)
 {
-	uint32_t bucket_idx;
-	hash_sig_t alt_hash;
-	struct rte_hash_bucket *bkt;
-	int32_t ret;
-
-	bucket_idx = sig & h->bucket_bitmask;
-	bkt = &h->buckets[bucket_idx];
+	uint32_t prim_bucket_idx, sec_bucket_idx;
+	struct rte_hash_bucket *prim_bkt, *sec_bkt, *prev_bkt, *last_bkt;
+	struct rte_hash_bucket *cur_bkt;
+	int pos;
+	int32_t ret, i;
+	uint16_t short_sig;
+
+	short_sig = get_short_sig(sig);
+	prim_bucket_idx = get_prim_bucket_index(h, sig);
+	sec_bucket_idx = get_alt_bucket_index(h, prim_bucket_idx, short_sig);
+	prim_bkt = &h->buckets[prim_bucket_idx];
 
 	__hash_rw_writer_lock(h);
 	/* look for key in primary bucket */
-	ret = search_and_remove(h, key, bkt, sig);
+	ret = search_and_remove(h, key, prim_bkt, short_sig, &pos);
 	if (ret != -1) {
-		__hash_rw_writer_unlock(h);
-		return ret;
+		__rte_hash_compact_ll(prim_bkt, pos);
+		last_bkt = prim_bkt->next;
+		prev_bkt = prim_bkt;
+		goto return_bkt;
 	}
 
 	/* Calculate secondary hash */
-	alt_hash = rte_hash_secondary_hash(sig);
-	bucket_idx = alt_hash & h->bucket_bitmask;
-	bkt = &h->buckets[bucket_idx];
+	sec_bkt = &h->buckets[sec_bucket_idx];
 
-	/* look for key in secondary bucket */
-	ret = search_and_remove(h, key, bkt, alt_hash);
-	if (ret != -1) {
+	FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
+		ret = search_and_remove(h, key, cur_bkt, short_sig, &pos);
+		if (ret != -1) {
+			__rte_hash_compact_ll(cur_bkt, pos);
+			last_bkt = sec_bkt->next;
+			prev_bkt = sec_bkt;
+			goto return_bkt;
+		}
+	}
+
+	__hash_rw_writer_unlock(h);
+	return -ENOENT;
+
+/* Search last bucket to see if empty to be recycled */
+return_bkt:
+	if (!last_bkt) {
 		__hash_rw_writer_unlock(h);
 		return ret;
 	}
+	while (last_bkt->next) {
+		prev_bkt = last_bkt;
+		last_bkt = last_bkt->next;
+	}
+
+	for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
+		if (last_bkt->key_idx[i] != EMPTY_SLOT)
+			break;
+	}
+	/* found empty bucket and recycle */
+	if (i == RTE_HASH_BUCKET_ENTRIES) {
+		prev_bkt->next = last_bkt->next = NULL;
+		uint32_t index = last_bkt - h->buckets_ext + 1;
+		rte_ring_sp_enqueue(h->free_ext_bkts, (void *)(uintptr_t)index);
+	}
 
 	__hash_rw_writer_unlock(h);
-	return -ENOENT;
+	return ret;
 }
 
 int32_t
@@ -1080,59 +1454,76 @@ rte_hash_get_key_with_position(const struct rte_hash *h, const int32_t position,
 	return 0;
 }
 
+int __rte_experimental
+rte_hash_free_key_with_position(const struct rte_hash *h,
+				const int32_t position)
+{
+	RETURN_IF_TRUE(((h == NULL) || (position == EMPTY_SLOT)), -EINVAL);
+
+	unsigned int lcore_id, n_slots;
+	struct lcore_cache *cached_free_slots;
+	const int32_t total_entries = h->num_buckets * RTE_HASH_BUCKET_ENTRIES;
+
+	/* Out of bounds */
+	if (position >= total_entries)
+		return -EINVAL;
+
+	if (h->use_local_cache) {
+		lcore_id = rte_lcore_id();
+		cached_free_slots = &h->local_free_slots[lcore_id];
+		/* Cache full, need to free it. */
+		if (cached_free_slots->len == LCORE_CACHE_SIZE) {
+			/* Need to enqueue the free slots in global ring. */
+			n_slots = rte_ring_mp_enqueue_burst(h->free_slots,
+						cached_free_slots->objs,
+						LCORE_CACHE_SIZE, NULL);
+			cached_free_slots->len -= n_slots;
+		}
+		/* Put index of new free slot in cache. */
+		cached_free_slots->objs[cached_free_slots->len] =
+					(void *)((uintptr_t)position);
+		cached_free_slots->len++;
+	} else {
+		rte_ring_sp_enqueue(h->free_slots,
+				(void *)((uintptr_t)position));
+	}
+
+	return 0;
+}
+
 static inline void
 compare_signatures(uint32_t *prim_hash_matches, uint32_t *sec_hash_matches,
 			const struct rte_hash_bucket *prim_bkt,
 			const struct rte_hash_bucket *sec_bkt,
-			hash_sig_t prim_hash, hash_sig_t sec_hash,
+			uint16_t sig,
 			enum rte_hash_sig_compare_function sig_cmp_fn)
 {
 	unsigned int i;
 
+	/* For match mask the first bit of every two bits indicates the match */
 	switch (sig_cmp_fn) {
-#ifdef RTE_MACHINE_CPUFLAG_AVX2
-	case RTE_HASH_COMPARE_AVX2:
-		*prim_hash_matches = _mm256_movemask_ps((__m256)_mm256_cmpeq_epi32(
-				_mm256_load_si256(
-					(__m256i const *)prim_bkt->sig_current),
-				_mm256_set1_epi32(prim_hash)));
-		*sec_hash_matches = _mm256_movemask_ps((__m256)_mm256_cmpeq_epi32(
-				_mm256_load_si256(
-					(__m256i const *)sec_bkt->sig_current),
-				_mm256_set1_epi32(sec_hash)));
-		break;
-#endif
 #ifdef RTE_MACHINE_CPUFLAG_SSE2
 	case RTE_HASH_COMPARE_SSE:
-		/* Compare the first 4 signatures in the bucket */
-		*prim_hash_matches = _mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+		/* Compare all signatures in the bucket */
+		*prim_hash_matches = _mm_movemask_epi8(_mm_cmpeq_epi16(
 				_mm_load_si128(
 					(__m128i const *)prim_bkt->sig_current),
-				_mm_set1_epi32(prim_hash)));
-		*prim_hash_matches |= (_mm_movemask_ps((__m128)_mm_cmpeq_epi16(
-				_mm_load_si128(
-					(__m128i const *)&prim_bkt->sig_current[4]),
-				_mm_set1_epi32(prim_hash)))) << 4;
-		/* Compare the first 4 signatures in the bucket */
-		*sec_hash_matches = _mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+				_mm_set1_epi16(sig)));
+		/* Compare all signatures in the bucket */
+		*sec_hash_matches = _mm_movemask_epi8(_mm_cmpeq_epi16(
 				_mm_load_si128(
 					(__m128i const *)sec_bkt->sig_current),
-				_mm_set1_epi32(sec_hash)));
-		*sec_hash_matches |= (_mm_movemask_ps((__m128)_mm_cmpeq_epi16(
-				_mm_load_si128(
-					(__m128i const *)&sec_bkt->sig_current[4]),
-				_mm_set1_epi32(sec_hash)))) << 4;
+				_mm_set1_epi16(sig)));
 		break;
 #endif
 	default:
 		for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
 			*prim_hash_matches |=
-				((prim_hash == prim_bkt->sig_current[i]) << i);
+				((sig == prim_bkt->sig_current[i]) << (i << 1));
 			*sec_hash_matches |=
-				((sec_hash == sec_bkt->sig_current[i]) << i);
+				((sig == sec_bkt->sig_current[i]) << (i << 1));
 		}
 	}
-
 }
 
 #define PREFETCH_OFFSET 4
@@ -1143,12 +1534,18 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 {
 	uint64_t hits = 0;
 	int32_t i;
+	int32_t ret;
 	uint32_t prim_hash[RTE_HASH_LOOKUP_BULK_MAX];
-	uint32_t sec_hash[RTE_HASH_LOOKUP_BULK_MAX];
+	uint32_t prim_index[RTE_HASH_LOOKUP_BULK_MAX];
+	uint32_t sec_index[RTE_HASH_LOOKUP_BULK_MAX];
+	uint16_t sig[RTE_HASH_LOOKUP_BULK_MAX];
 	const struct rte_hash_bucket *primary_bkt[RTE_HASH_LOOKUP_BULK_MAX];
 	const struct rte_hash_bucket *secondary_bkt[RTE_HASH_LOOKUP_BULK_MAX];
 	uint32_t prim_hitmask[RTE_HASH_LOOKUP_BULK_MAX] = {0};
 	uint32_t sec_hitmask[RTE_HASH_LOOKUP_BULK_MAX] = {0};
+	struct rte_hash_bucket *cur_bkt, *next_bkt;
+	void *pdata[RTE_HASH_LOOKUP_BULK_MAX];
+	uint32_t cnt_b, cnt_a;
 
 	/* Prefetch first keys */
 	for (i = 0; i < PREFETCH_OFFSET && i < num_keys; i++)
@@ -1162,10 +1559,13 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 		rte_prefetch0(keys[i + PREFETCH_OFFSET]);
 
 		prim_hash[i] = rte_hash_hash(h, keys[i]);
-		sec_hash[i] = rte_hash_secondary_hash(prim_hash[i]);
 
-		primary_bkt[i] = &h->buckets[prim_hash[i] & h->bucket_bitmask];
-		secondary_bkt[i] = &h->buckets[sec_hash[i] & h->bucket_bitmask];
+		sig[i] = get_short_sig(prim_hash[i]);
+		prim_index[i] = get_prim_bucket_index(h, prim_hash[i]);
+		sec_index[i] = get_alt_bucket_index(h, prim_index[i], sig[i]);
+
+		primary_bkt[i] = &h->buckets[prim_index[i]];
+		secondary_bkt[i] = &h->buckets[sec_index[i]];
 
 		rte_prefetch0(primary_bkt[i]);
 		rte_prefetch0(secondary_bkt[i]);
@@ -1174,96 +1574,178 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 	/* Calculate and prefetch rest of the buckets */
 	for (; i < num_keys; i++) {
 		prim_hash[i] = rte_hash_hash(h, keys[i]);
-		sec_hash[i] = rte_hash_secondary_hash(prim_hash[i]);
 
-		primary_bkt[i] = &h->buckets[prim_hash[i] & h->bucket_bitmask];
-		secondary_bkt[i] = &h->buckets[sec_hash[i] & h->bucket_bitmask];
+		sig[i] = get_short_sig(prim_hash[i]);
+		prim_index[i] = get_prim_bucket_index(h, prim_hash[i]);
+		sec_index[i] = get_alt_bucket_index(h, prim_index[i], sig[i]);
+
+		primary_bkt[i] = &h->buckets[prim_index[i]];
+		secondary_bkt[i] = &h->buckets[sec_index[i]];
 
 		rte_prefetch0(primary_bkt[i]);
 		rte_prefetch0(secondary_bkt[i]);
 	}
 
 	__hash_rw_reader_lock(h);
-	/* Compare signatures and prefetch key slot of first hit */
-	for (i = 0; i < num_keys; i++) {
-		compare_signatures(&prim_hitmask[i], &sec_hitmask[i],
+	do {
+		/* Load the table change counter before the lookup
+		 * starts. Acquire semantics will make sure that
+		 * loads in compare_signatures are not hoisted.
+		 */
+		cnt_b = __atomic_load_n(h->tbl_chng_cnt,
+					__ATOMIC_ACQUIRE);
+
+		/* Compare signatures and prefetch key slot of first hit */
+		for (i = 0; i < num_keys; i++) {
+			compare_signatures(&prim_hitmask[i], &sec_hitmask[i],
 				primary_bkt[i], secondary_bkt[i],
-				prim_hash[i], sec_hash[i], h->sig_cmp_fn);
-
-		if (prim_hitmask[i]) {
-			uint32_t first_hit = __builtin_ctzl(prim_hitmask[i]);
-			uint32_t key_idx = primary_bkt[i]->key_idx[first_hit];
-			const struct rte_hash_key *key_slot =
-				(const struct rte_hash_key *)(
-				(const char *)h->key_store +
-				key_idx * h->key_entry_size);
-			rte_prefetch0(key_slot);
-			continue;
-		}
+				sig[i], h->sig_cmp_fn);
+
+			if (prim_hitmask[i]) {
+				uint32_t first_hit =
+						__builtin_ctzl(prim_hitmask[i])
+						>> 1;
+				uint32_t key_idx =
+					primary_bkt[i]->key_idx[first_hit];
+				const struct rte_hash_key *key_slot =
+					(const struct rte_hash_key *)(
+					(const char *)h->key_store +
+					key_idx * h->key_entry_size);
+				rte_prefetch0(key_slot);
+				continue;
+			}
 
-		if (sec_hitmask[i]) {
-			uint32_t first_hit = __builtin_ctzl(sec_hitmask[i]);
-			uint32_t key_idx = secondary_bkt[i]->key_idx[first_hit];
-			const struct rte_hash_key *key_slot =
-				(const struct rte_hash_key *)(
-				(const char *)h->key_store +
-				key_idx * h->key_entry_size);
-			rte_prefetch0(key_slot);
+			if (sec_hitmask[i]) {
+				uint32_t first_hit =
+						__builtin_ctzl(sec_hitmask[i])
+						>> 1;
+				uint32_t key_idx =
+					secondary_bkt[i]->key_idx[first_hit];
+				const struct rte_hash_key *key_slot =
+					(const struct rte_hash_key *)(
+					(const char *)h->key_store +
+					key_idx * h->key_entry_size);
+				rte_prefetch0(key_slot);
+			}
 		}
-	}
 
-	/* Compare keys, first hits in primary first */
-	for (i = 0; i < num_keys; i++) {
-		positions[i] = -ENOENT;
-		while (prim_hitmask[i]) {
-			uint32_t hit_index = __builtin_ctzl(prim_hitmask[i]);
-
-			uint32_t key_idx = primary_bkt[i]->key_idx[hit_index];
-			const struct rte_hash_key *key_slot =
-				(const struct rte_hash_key *)(
-				(const char *)h->key_store +
-				key_idx * h->key_entry_size);
-			/*
-			 * If key index is 0, do not compare key,
-			 * as it is checking the dummy slot
-			 */
-			if (!!key_idx & !rte_hash_cmp_eq(key_slot->key, keys[i], h)) {
-				if (data != NULL)
-					data[i] = key_slot->pdata;
+		/* Compare keys, first hits in primary first */
+		for (i = 0; i < num_keys; i++) {
+			positions[i] = -ENOENT;
+			while (prim_hitmask[i]) {
+				uint32_t hit_index =
+						__builtin_ctzl(prim_hitmask[i])
+						>> 1;
+				uint32_t key_idx =
+				__atomic_load_n(
+					&primary_bkt[i]->key_idx[hit_index],
+					__ATOMIC_ACQUIRE);
+				const struct rte_hash_key *key_slot =
+					(const struct rte_hash_key *)(
+					(const char *)h->key_store +
+					key_idx * h->key_entry_size);
+
+				if (key_idx != EMPTY_SLOT)
+					pdata[i] = __atomic_load_n(
+							&key_slot->pdata,
+							__ATOMIC_ACQUIRE);
+				/*
+				 * If key index is 0, do not compare key,
+				 * as it is checking the dummy slot
+				 */
+				if (!!key_idx &
+					!rte_hash_cmp_eq(
+						key_slot->key, keys[i], h)) {
+					if (data != NULL)
+						data[i] = pdata[i];
+
+					hits |= 1ULL << i;
+					positions[i] = key_idx - 1;
+					goto next_key;
+				}
+				prim_hitmask[i] &= ~(3ULL << (hit_index << 1));
+			}
 
-				hits |= 1ULL << i;
-				positions[i] = key_idx - 1;
-				goto next_key;
+			while (sec_hitmask[i]) {
+				uint32_t hit_index =
+						__builtin_ctzl(sec_hitmask[i])
+						>> 1;
+				uint32_t key_idx =
+				__atomic_load_n(
+					&secondary_bkt[i]->key_idx[hit_index],
+					__ATOMIC_ACQUIRE);
+				const struct rte_hash_key *key_slot =
+					(const struct rte_hash_key *)(
+					(const char *)h->key_store +
+					key_idx * h->key_entry_size);
+
+				if (key_idx != EMPTY_SLOT)
+					pdata[i] = __atomic_load_n(
+							&key_slot->pdata,
+							__ATOMIC_ACQUIRE);
+				/*
+				 * If key index is 0, do not compare key,
+				 * as it is checking the dummy slot
+				 */
+
+				if (!!key_idx &
+					!rte_hash_cmp_eq(
+						key_slot->key, keys[i], h)) {
+					if (data != NULL)
+						data[i] = pdata[i];
+
+					hits |= 1ULL << i;
+					positions[i] = key_idx - 1;
+					goto next_key;
+				}
+				sec_hitmask[i] &= ~(3ULL << (hit_index << 1));
 			}
-			prim_hitmask[i] &= ~(1 << (hit_index));
+next_key:
+			continue;
 		}
 
-		while (sec_hitmask[i]) {
-			uint32_t hit_index = __builtin_ctzl(sec_hitmask[i]);
-
-			uint32_t key_idx = secondary_bkt[i]->key_idx[hit_index];
-			const struct rte_hash_key *key_slot =
-				(const struct rte_hash_key *)(
-				(const char *)h->key_store +
-				key_idx * h->key_entry_size);
-			/*
-			 * If key index is 0, do not compare key,
-			 * as it is checking the dummy slot
-			 */
-
-			if (!!key_idx & !rte_hash_cmp_eq(key_slot->key, keys[i], h)) {
-				if (data != NULL)
-					data[i] = key_slot->pdata;
+		/* The loads of sig_current in compare_signatures
+		 * should not move below the load from tbl_chng_cnt.
+		 */
+		__atomic_thread_fence(__ATOMIC_ACQUIRE);
+		/* Re-read the table change counter to check if the
+		 * table has changed during search. If yes, re-do
+		 * the search.
+		 * This load should not get hoisted. The load
+		 * acquires on cnt_b, primary key index and secondary
+		 * key index will make sure that it does not get
+		 * hoisted.
+		 */
+		cnt_a = __atomic_load_n(h->tbl_chng_cnt,
+					__ATOMIC_ACQUIRE);
+	} while (cnt_b != cnt_a);
+
+	/* all found, do not need to go through ext bkt */
+	if ((hits == ((1ULL << num_keys) - 1)) || !h->ext_table_support) {
+		if (hit_mask != NULL)
+			*hit_mask = hits;
+		__hash_rw_reader_unlock(h);
+		return;
+	}
 
+	/* need to check ext buckets for match */
+	for (i = 0; i < num_keys; i++) {
+		if ((hits & (1ULL << i)) != 0)
+			continue;
+		next_bkt = secondary_bkt[i]->next;
+		FOR_EACH_BUCKET(cur_bkt, next_bkt) {
+			if (data != NULL)
+				ret = search_one_bucket(h, keys[i],
+						sig[i], &data[i], cur_bkt);
+			else
+				ret = search_one_bucket(h, keys[i],
+						sig[i], NULL, cur_bkt);
+			if (ret != -1) {
+				positions[i] = ret;
 				hits |= 1ULL << i;
-				positions[i] = key_idx - 1;
-				goto next_key;
+				break;
 			}
-			sec_hitmask[i] &= ~(1 << (hit_index));
 		}
-
-next_key:
-		continue;
 	}
 
 	__hash_rw_reader_unlock(h);
@@ -1308,27 +1790,30 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32
 
 	RETURN_IF_TRUE(((h == NULL) || (next == NULL)), -EINVAL);
 
-	const uint32_t total_entries = h->num_buckets * RTE_HASH_BUCKET_ENTRIES;
-	/* Out of bounds */
-	if (*next >= total_entries)
-		return -ENOENT;
+	const uint32_t total_entries_main = h->num_buckets *
+							RTE_HASH_BUCKET_ENTRIES;
+	const uint32_t total_entries = total_entries_main << 1;
+
+	/* Out of bounds of all buckets (both main table and ext table) */
+	if (*next >= total_entries_main)
+		goto extend_table;
 
 	/* Calculate bucket and index of current iterator */
 	bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
 	idx = *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) {
+	while ((position = __atomic_load_n(&h->buckets[bucket_idx].key_idx[idx],
+					__ATOMIC_ACQUIRE)) == EMPTY_SLOT) {
 		(*next)++;
 		/* End of table */
-		if (*next == total_entries)
-			return -ENOENT;
+		if (*next == total_entries_main)
+			goto extend_table;
 		bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
 		idx = *next % RTE_HASH_BUCKET_ENTRIES;
 	}
+
 	__hash_rw_reader_lock(h);
-	/* 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);
 	/* Return key and data */
@@ -1341,4 +1826,34 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32
 	(*next)++;
 
 	return position - 1;
+
+/* Begin to iterate extendable buckets */
+extend_table:
+	/* Out of total bound or if ext bucket feature is not enabled */
+	if (*next >= total_entries || !h->ext_table_support)
+		return -ENOENT;
+
+	bucket_idx = (*next - total_entries_main) / RTE_HASH_BUCKET_ENTRIES;
+	idx = (*next - total_entries_main) % RTE_HASH_BUCKET_ENTRIES;
+
+	while ((position = h->buckets_ext[bucket_idx].key_idx[idx]) == EMPTY_SLOT) {
+		(*next)++;
+		if (*next == total_entries)
+			return -ENOENT;
+		bucket_idx = (*next - total_entries_main) /
+						RTE_HASH_BUCKET_ENTRIES;
+		idx = (*next - total_entries_main) % RTE_HASH_BUCKET_ENTRIES;
+	}
+	__hash_rw_reader_lock(h);
+	next_key = (struct rte_hash_key *) ((char *)h->key_store +
+				position * h->key_entry_size);
+	/* Return key and data */
+	*key = next_key->key;
+	*data = next_key->pdata;
+
+	__hash_rw_reader_unlock(h);
+
+	/* Increment iterator */
+	(*next)++;
+	return position - 1;
 }
diff --git a/lib/librte_hash/rte_cuckoo_hash.h b/lib/librte_hash/rte_cuckoo_hash.h
index b43f467d..5dfbbc48 100644
--- a/lib/librte_hash/rte_cuckoo_hash.h
+++ b/lib/librte_hash/rte_cuckoo_hash.h
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2016 Intel Corporation
+ * Copyright(c) 2018 Arm Limited
  */
 
 /* rte_cuckoo_hash.h
@@ -104,8 +105,6 @@ const rte_hash_cmp_eq_t cmp_jump_table[NUM_KEY_CMP_CASES] = {
 
 #define LCORE_CACHE_SIZE		64
 
-#define RTE_HASH_MAX_PUSHES             100
-
 #define RTE_HASH_BFS_QUEUE_MAX_LEN       1000
 
 #define RTE_XABORT_CUCKOO_PATH_INVALIDED 0x4
@@ -125,25 +124,24 @@ struct rte_hash_key {
 	};
 	/* Variable key size */
 	char key[0];
-} __attribute__((aligned(KEY_ALIGNMENT)));
+};
 
 /* All different signature compare functions */
 enum rte_hash_sig_compare_function {
 	RTE_HASH_COMPARE_SCALAR = 0,
 	RTE_HASH_COMPARE_SSE,
-	RTE_HASH_COMPARE_AVX2,
 	RTE_HASH_COMPARE_NUM
 };
 
 /** Bucket structure */
 struct rte_hash_bucket {
-	hash_sig_t sig_current[RTE_HASH_BUCKET_ENTRIES];
+	uint16_t sig_current[RTE_HASH_BUCKET_ENTRIES];
 
 	uint32_t key_idx[RTE_HASH_BUCKET_ENTRIES];
 
-	hash_sig_t sig_alt[RTE_HASH_BUCKET_ENTRIES];
-
 	uint8_t flag[RTE_HASH_BUCKET_ENTRIES];
+
+	void *next;
 } __rte_cache_aligned;
 
 /** A hash table structure. */
@@ -164,10 +162,23 @@ struct rte_hash {
 	/**< Length of hash key. */
 	uint8_t hw_trans_mem_support;
 	/**< If hardware transactional memory is used. */
-	uint8_t multi_writer_support;
-	/**< If multi-writer support is enabled. */
+	uint8_t use_local_cache;
+	/**< If multi-writer support is enabled, use local cache
+	 * to allocate key-store slots.
+	 */
 	uint8_t readwrite_concur_support;
 	/**< If read-write concurrency support is enabled */
+	uint8_t ext_table_support;     /**< Enable extendable bucket table */
+	uint8_t no_free_on_del;
+	/**< If key index should be freed on calling rte_hash_del_xxx APIs.
+	 * If this is set, rte_hash_free_key_with_position must be called to
+	 * free the key index associated with the deleted entry.
+	 * This flag is enabled by default.
+	 */
+	uint8_t readwrite_concur_lf_support;
+	/**< If read-write concurrency lock free support is enabled */
+	uint8_t writer_takes_lock;
+	/**< Indicates if the writer threads need to take lock */
 	rte_hash_function hash_func;    /**< Function used to calculate hash. */
 	uint32_t hash_func_init_val;    /**< Init value used by hash_func. */
 	rte_hash_cmp_eq_t rte_hash_custom_cmp_eq;
@@ -186,10 +197,15 @@ struct rte_hash {
 	 * to the key table.
 	 */
 	rte_rwlock_t *readwrite_lock; /**< Read-write lock thread-safety. */
+	struct rte_hash_bucket *buckets_ext; /**< Extra buckets array */
+	struct rte_ring *free_ext_bkts; /**< Ring of indexes of free buckets */
+	uint32_t *tbl_chng_cnt;
+	/**< Indicates if the hash table changed from last read. */
 } __rte_cache_aligned;
 
 struct queue_node {
 	struct rte_hash_bucket *bkt; /* Current bucket on the bfs search */
+	uint32_t cur_bkt_idx;
 
 	struct queue_node *prev;     /* Parent(bucket) in search path */
 	int prev_slot;               /* Parent(slot) in search path */
diff --git a/lib/librte_hash/rte_hash.h b/lib/librte_hash/rte_hash.h
index 9e7d9315..c93d1a13 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
@@ -37,7 +39,27 @@ extern "C" {
 /** Flag to support reader writer concurrency */
 #define RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY 0x04
 
-/** Signature of key that is stored internally. */
+/** Flag to indicate the extendabe bucket table feature should be used */
+#define RTE_HASH_EXTRA_FLAGS_EXT_TABLE 0x08
+
+/** Flag to disable freeing of key index on hash delete.
+ * Refer to rte_hash_del_xxx APIs for more details.
+ * This is enabled by default when RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF
+ * is enabled.
+ */
+#define RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL 0x10
+
+/** Flag to support lock free reader writer concurrency. Both single writer
+ * and multi writer use cases are supported.
+ * Currently, extendable bucket table feature is not supported with
+ * this feature.
+ */
+#define RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF 0x20
+
+/**
+ * The type of hash value of a key.
+ * It should be a value of at least 32bit with fully random pattern.
+ */
 typedef uint32_t hash_sig_t;
 
 /** Type of function that can be used for calculating the hash value. */
@@ -119,7 +141,12 @@ void
 rte_hash_free(struct rte_hash *h);
 
 /**
- * Reset all hash structure, by zeroing all entries
+ * Reset all hash structure, by zeroing all entries.
+ * When RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled,
+ * it is application's responsibility to make sure that
+ * none of the readers are referencing the hash table
+ * while calling this API.
+ *
  * @param h
  *   Hash table to reset
  */
@@ -143,6 +170,11 @@ rte_hash_count(const struct rte_hash *h);
  * and should only be called from one thread by default.
  * Thread safety can be enabled by setting flag during
  * table creation.
+ * If the key exists already in the table, this API updates its value
+ * with 'data' passed in this API. It is the responsibility of
+ * the application to manage any memory associated with the old value.
+ * The readers might still be using the old value even after this API
+ * has returned.
  *
  * @param h
  *   Hash table to add the key to.
@@ -165,6 +197,11 @@ rte_hash_add_key_data(const struct rte_hash *h, const void *key, void *data);
  * and should only be called from one thread by default.
  * Thread safety can be enabled by setting flag during
  * table creation.
+ * If the key exists already in the table, this API updates its value
+ * with 'data' passed in this API. It is the responsibility of
+ * the application to manage any memory associated with the old value.
+ * The readers might still be using the old value even after this API
+ * has returned.
  *
  * @param h
  *   Hash table to add the key to.
@@ -230,6 +267,14 @@ rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key, hash_sig_t
  * and should only be called from one thread by default.
  * Thread safety can be enabled by setting flag during
  * table creation.
+ * If RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL or
+ * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled,
+ * the key index returned by rte_hash_add_key_xxx APIs will not be
+ * freed by this API. rte_hash_free_key_with_position API must be called
+ * additionally to free the index associated with the key.
+ * rte_hash_free_key_with_position API should be called after all
+ * the readers have stopped referencing the entry corresponding to
+ * this key. RCU mechanisms could be used to determine such a state.
  *
  * @param h
  *   Hash table to remove the key from.
@@ -251,6 +296,14 @@ rte_hash_del_key(const struct rte_hash *h, const void *key);
  * and should only be called from one thread by default.
  * Thread safety can be enabled by setting flag during
  * table creation.
+ * If RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL or
+ * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled,
+ * the key index returned by rte_hash_add_key_xxx APIs will not be
+ * freed by this API. rte_hash_free_key_with_position API must be called
+ * additionally to free the index associated with the key.
+ * rte_hash_free_key_with_position API should be called after all
+ * the readers have stopped referencing the entry corresponding to
+ * this key. RCU mechanisms could be used to determine such a state.
  *
  * @param h
  *   Hash table to remove the key from.
@@ -290,6 +343,34 @@ rte_hash_get_key_with_position(const struct rte_hash *h, const int32_t position,
 			       void **key);
 
 /**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Free a hash key in the hash table given the position
+ * of the key. This operation is not multi-thread safe and should
+ * only be called from one thread by default. Thread safety
+ * can be enabled by setting flag during table creation.
+ * If RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL or
+ * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled,
+ * the key index returned by rte_hash_del_key_xxx APIs must be freed
+ * using this API. This API should be called after all the readers
+ * have stopped referencing the entry corresponding to this key.
+ * RCU mechanisms could be used to determine such a state.
+ * This API does not validate if the key is already freed.
+ *
+ * @param h
+ *   Hash table to free the key from.
+ * @param position
+ *   Position returned when the key was deleted.
+ * @return
+ *   - 0 if freed successfully
+ *   - -EINVAL if the parameters are invalid.
+ */
+int __rte_experimental
+rte_hash_free_key_with_position(const struct rte_hash *h,
+				const int32_t position);
+
+/**
  * Find a key-value pair in the hash table.
  * This operation is multi-thread safe with regarding to other lookup threads.
  * Read-write concurrency can be enabled by setting flag during
diff --git a/lib/librte_hash/rte_hash_version.map b/lib/librte_hash/rte_hash_version.map
index e216ac8e..734ae28b 100644
--- a/lib/librte_hash/rte_hash_version.map
+++ b/lib/librte_hash/rte_hash_version.map
@@ -53,3 +53,10 @@ DPDK_18.08 {
 	rte_hash_count;
 
 } DPDK_16.07;
+
+EXPERIMENTAL {
+	global:
+
+	rte_hash_free_key_with_position;
+
+};