Re: [dpdk-dev] [RFC v2] lib/hash: integrate RCU QSBR

[Dharmik Thakkar <Dharmik.Thakkar@arm.com>]

CI has reported some compilation issues for this patch. I will resolve these issues once the RFC patch is approved.

Thank you!

> On Aug 18, 2020, at 11:05 PM, Dharmik Thakkar <Dharmik.Thakkar@arm.com> wrote:
> 
> Integrate RCU QSBR to make it easier for the applications to use lock
> free algorithm.
> 
> Resource reclamation implementation was split from the original
> series, and has already been part of RCU library. Rework the series
> to base hash integration on RCU reclamation APIs.
> 
> Refer 'Resource reclamation framework for DPDK' available at [1]
> to understand various aspects of integrating RCU library
> into other libraries.
> 
> [1] https://doc.dpdk.org/guides/prog_guide/rcu_lib.html
> 
> Introduce a new API rte_hash_rcu_qsbr_add for application to
> register a RCU variable that hash library will use.
> 
> Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
> v2:
> - Remove defer queue related functions and use resource reclamation
>   APIs from the RCU QSBR library instead
> 
> - Remove patch (net/ixgbe: avoid multpile definitions of 'bool')
>   from the series as it is already accepted
> 
> ---
> lib/Makefile                         |   2 +-
> lib/librte_hash/Makefile             |   2 +-
> lib/librte_hash/meson.build          |   1 +
> lib/librte_hash/rte_cuckoo_hash.c    | 291 +++++++++++++++++++++------
> lib/librte_hash/rte_cuckoo_hash.h    |   8 +
> lib/librte_hash/rte_hash.h           |  75 ++++++-
> lib/librte_hash/rte_hash_version.map |   2 +-
> 7 files changed, 308 insertions(+), 73 deletions(-)
> 
> diff --git a/lib/Makefile b/lib/Makefile
> index 8f5b68a2d469..dffe31c829f0 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -51,7 +51,7 @@ DIRS-$(CONFIG_RTE_LIBRTE_VHOST) += librte_vhost
> DEPDIRS-librte_vhost := librte_eal librte_mempool librte_mbuf librte_ethdev \
> 			librte_net librte_hash librte_cryptodev
> DIRS-$(CONFIG_RTE_LIBRTE_HASH) += librte_hash
> -DEPDIRS-librte_hash := librte_eal librte_ring
> +DEPDIRS-librte_hash := librte_eal librte_ring librte_rcu
> DIRS-$(CONFIG_RTE_LIBRTE_EFD) += librte_efd
> DEPDIRS-librte_efd := librte_eal librte_ring librte_hash
> DIRS-$(CONFIG_RTE_LIBRTE_RIB) += librte_rib
> diff --git a/lib/librte_hash/Makefile b/lib/librte_hash/Makefile
> index ec9f86499262..10e697f48652 100644
> --- a/lib/librte_hash/Makefile
> +++ b/lib/librte_hash/Makefile
> @@ -8,7 +8,7 @@ LIB = librte_hash.a
> 
> CFLAGS += -O3
> CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR)
> -LDLIBS += -lrte_eal -lrte_ring
> +LDLIBS += -lrte_eal -lrte_ring -lrte_rcu
> 
> EXPORT_MAP := rte_hash_version.map
> 
> diff --git a/lib/librte_hash/meson.build b/lib/librte_hash/meson.build
> index 6ab46ae9d768..0977a63fd279 100644
> --- a/lib/librte_hash/meson.build
> +++ b/lib/librte_hash/meson.build
> @@ -10,3 +10,4 @@ headers = files('rte_crc_arm64.h',
> 
> sources = files('rte_cuckoo_hash.c', 'rte_fbk_hash.c')
> deps += ['ring']
> +deps += ['rcu']
> diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
> index 0a6d474713a2..01c2cbe0e38b 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.c
> +++ b/lib/librte_hash/rte_cuckoo_hash.c
> @@ -52,6 +52,11 @@ static struct rte_tailq_elem rte_hash_tailq = {
> };
> EAL_REGISTER_TAILQ(rte_hash_tailq)
> 
> +struct __rte_hash_rcu_dq_entry {
> +	uint32_t key_idx;
> +	uint32_t ext_bkt_idx; /**< Extended bkt index */
> +};
> +
> struct rte_hash *
> rte_hash_find_existing(const char *name)
> {
> @@ -210,7 +215,10 @@ rte_hash_create(const struct rte_hash_parameters *params)
> 
> 	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF) {
> 		readwrite_concur_lf_support = 1;
> -		/* Enable not freeing internal memory/index on delete */
> +		/* Enable not freeing internal memory/index on delete.
> +		 * If internal RCU is enabled, freeing of internal memory/index
> +		 * is done on delete
> +		 */
> 		no_free_on_del = 1;
> 	}
> 
> @@ -505,6 +513,10 @@ rte_hash_free(struct rte_hash *h)
> 
> 	rte_mcfg_tailq_write_unlock();
> 
> +	/* RCU clean up. */
> +	if (h->dq)
> +		rte_rcu_qsbr_dq_delete(h->dq);
> +
> 	if (h->use_local_cache)
> 		rte_free(h->local_free_slots);
> 	if (h->writer_takes_lock)
> @@ -612,6 +624,16 @@ rte_hash_reset(struct rte_hash *h)
> 		return;
> 
> 	__hash_rw_writer_lock(h);
> +
> +	/* RCU clean up. */
> +	if (h->hash_rcu_cfg->v) {
> +		rte_rcu_qsbr_dq_delete(h->dq);
> +		h->dq = NULL;
> +		if (rte_hash_rcu_qsbr_add(h, h->hash_rcu_cfg) < 0) {
> +			RTE_LOG(ERR, HASH, "RCU init failed\n");
> +			return;
> +		}
> +	}
> 	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;
> @@ -952,6 +974,37 @@ rte_hash_cuckoo_make_space_mw(const struct rte_hash *h,
> 	return -ENOSPC;
> }
> 
> +static inline uint32_t
> +alloc_slot(const struct rte_hash *h, struct lcore_cache *cached_free_slots)
> +{
> +	unsigned int  n_slots;
> +	uint32_t slot_id;
> +	if (h->use_local_cache) {
> +		/* Try to get a free slot from the local cache */
> +		if (cached_free_slots->len == 0) {
> +			/* Need to get another burst of free slots from global ring */
> +			n_slots = rte_ring_mc_dequeue_burst_elem(h->free_slots,
> +					cached_free_slots->objs,
> +					sizeof(uint32_t),
> +					LCORE_CACHE_SIZE, NULL);
> +			if (n_slots == 0)
> +				return EMPTY_SLOT;
> +
> +			cached_free_slots->len += n_slots;
> +		}
> +
> +		/* Get a free slot from the local cache */
> +		cached_free_slots->len--;
> +		slot_id = cached_free_slots->objs[cached_free_slots->len];
> +	} else {
> +		if (rte_ring_sc_dequeue_elem(h->free_slots, &slot_id,
> +						sizeof(uint32_t)) != 0)
> +			return EMPTY_SLOT;
> +	}
> +
> +	return slot_id;
> +}
> +
> static inline int32_t
> __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> 						hash_sig_t sig, void *data)
> @@ -963,7 +1016,6 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> 	uint32_t ext_bkt_id = 0;
> 	uint32_t slot_id;
> 	int ret;
> -	unsigned n_slots;
> 	unsigned lcore_id;
> 	unsigned int i;
> 	struct lcore_cache *cached_free_slots = NULL;
> @@ -1001,28 +1053,19 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> 	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 */
> -		if (cached_free_slots->len == 0) {
> -			/* Need to get another burst of free slots from global ring */
> -			n_slots = rte_ring_mc_dequeue_burst_elem(h->free_slots,
> -					cached_free_slots->objs,
> -					sizeof(uint32_t),
> -					LCORE_CACHE_SIZE, NULL);
> -			if (n_slots == 0) {
> -				return -ENOSPC;
> +	}
> +	slot_id = alloc_slot(h, cached_free_slots);
> +	if (slot_id == EMPTY_SLOT) {
> +		if (h->hash_rcu_cfg->v) {
> +			if (rte_rcu_qsbr_dq_reclaim(h->dq,
> +						    h->hash_rcu_cfg->reclaim_max,
> +						    NULL, NULL, NULL)
> +					== 0) {
> +				slot_id = alloc_slot(h, cached_free_slots);
> 			}
> -
> -			cached_free_slots->len += n_slots;
> 		}
> -
> -		/* Get a free slot from the local cache */
> -		cached_free_slots->len--;
> -		slot_id = cached_free_slots->objs[cached_free_slots->len];
> -	} else {
> -		if (rte_ring_sc_dequeue_elem(h->free_slots, &slot_id,
> -						sizeof(uint32_t)) != 0) {
> +		if (slot_id == EMPTY_SLOT)
> 			return -ENOSPC;
> -		}
> 	}
> 
> 	new_k = RTE_PTR_ADD(keys, slot_id * h->key_entry_size);
> @@ -1118,8 +1161,20 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> 	if (rte_ring_sc_dequeue_elem(h->free_ext_bkts, &ext_bkt_id,
> 						sizeof(uint32_t)) != 0 ||
> 					ext_bkt_id == 0) {
> -		ret = -ENOSPC;
> -		goto failure;
> +		if (h->hash_rcu_cfg->v) {
> +			if (rte_rcu_qsbr_dq_reclaim(h->dq,
> +						    h->hash_rcu_cfg->reclaim_max,
> +						    NULL, NULL, NULL)
> +					== 0) {
> +				rte_ring_sc_dequeue_elem(h->free_ext_bkts,
> +							 &ext_bkt_id,
> +							 sizeof(uint32_t));
> +			}
> +		}
> +		if (ext_bkt_id == 0) {
> +			ret = -ENOSPC;
> +			goto failure;
> +		}
> 	}
> 
> 	/* Use the first location of the new bucket */
> @@ -1395,12 +1450,12 @@ rte_hash_lookup_data(const struct rte_hash *h, const void *key, void **data)
> 	return __rte_hash_lookup_with_hash(h, key, rte_hash_hash(h, key), data);
> }
> 
> -static inline void
> -remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
> +static int
> +free_slot(const struct rte_hash *h, uint32_t slot_id)
> {
> 	unsigned lcore_id, n_slots;
> 	struct lcore_cache *cached_free_slots;
> -
> +	/* Return key indexes to free slot ring */
> 	if (h->use_local_cache) {
> 		lcore_id = rte_lcore_id();
> 		cached_free_slots = &h->local_free_slots[lcore_id];
> @@ -1411,18 +1466,122 @@ remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
> 						cached_free_slots->objs,
> 						sizeof(uint32_t),
> 						LCORE_CACHE_SIZE, NULL);
> -			ERR_IF_TRUE((n_slots == 0),
> -				"%s: could not enqueue free slots in global ring\n",
> -				__func__);
> +			RETURN_IF_TRUE((n_slots == 0), -EFAULT);
> 			cached_free_slots->len -= n_slots;
> 		}
> -		/* Put index of new free slot in cache. */
> -		cached_free_slots->objs[cached_free_slots->len] =
> -							bkt->key_idx[i];
> -		cached_free_slots->len++;
> +	}
> +
> +	enqueue_slot_back(h, cached_free_slots, slot_id);
> +	return 0;
> +}
> +
> +static void
> +__hash_rcu_qsbr_free_resource(void *p, void *e, unsigned int n)
> +{
> +	void *key_data = NULL;
> +	int ret;
> +	struct rte_hash_key *keys, *k;
> +	struct rte_hash *h = (struct rte_hash *)p;
> +	struct __rte_hash_rcu_dq_entry rcu_dq_entry =
> +			*((struct __rte_hash_rcu_dq_entry *)e);
> +
> +	RTE_SET_USED(n);
> +	keys = h->key_store;
> +
> +	k = (struct rte_hash_key *) ((char *)keys +
> +				rcu_dq_entry.key_idx * h->key_entry_size);
> +	key_data = k->pdata;
> +	if (h->hash_rcu_cfg->free_key_data_func)
> +		h->hash_rcu_cfg->free_key_data_func(h->hash_rcu_cfg->key_data_ptr,
> +						    key_data);
> +
> +	if (h->ext_table_support && rcu_dq_entry.ext_bkt_idx != EMPTY_SLOT)
> +		/* Recycle empty ext bkt to free list. */
> +		rte_ring_sp_enqueue_elem(h->free_ext_bkts,
> +			&rcu_dq_entry.ext_bkt_idx, sizeof(uint32_t));
> +
> +	/* Return key indexes to free slot ring */
> +	ret = free_slot(h, rcu_dq_entry.key_idx);
> +	if (ret < 0) {
> +		RTE_LOG(ERR, HASH,
> +			"%s: could not enqueue free slots in global ring\n",
> +				__func__);
> +	}
> +}
> +
> +int
> +rte_hash_rcu_qsbr_add(struct rte_hash *h,
> +				struct rte_hash_rcu_config *cfg)
> +{
> +	struct rte_rcu_qsbr_dq_parameters params = {0};
> +	char rcu_dq_name[RTE_RCU_QSBR_DQ_NAMESIZE];
> +	struct rte_hash_rcu_config *hash_rcu_cfg = NULL;
> +
> +	const uint32_t total_entries = h->use_local_cache ?
> +		h->entries + (RTE_MAX_LCORE - 1) * (LCORE_CACHE_SIZE - 1) + 1
> +							: h->entries + 1;
> +
> +	if ((h == NULL) || cfg == NULL) {
> +		rte_errno = EINVAL;
> +		return 1;
> +	}
> +
> +	hash_rcu_cfg = rte_zmalloc(NULL, sizeof(struct rte_hash_rcu_config), 0);
> +	if (hash_rcu_cfg == NULL) {
> +		RTE_LOG(ERR, HASH, "memory allocation failed\n");
> +		return 1;
> +	}
> +
> +	if (cfg->mode == RTE_HASH_QSBR_MODE_SYNC) {
> +		/* No other things to do. */
> +	} else if (cfg->mode == RTE_HASH_QSBR_MODE_DQ) {
> +		/* Init QSBR defer queue. */
> +		snprintf(rcu_dq_name, sizeof(rcu_dq_name),
> +					"HASH_RCU_%s", h->name);
> +		params.name = rcu_dq_name;
> +		params.size = cfg->dq_size;
> +		if (params.size == 0)
> +			params.size = total_entries;
> +		params.trigger_reclaim_limit = cfg->reclaim_thd;
> +		if (params.max_reclaim_size == 0)
> +			params.max_reclaim_size = RTE_HASH_RCU_DQ_RECLAIM_MAX;
> +		params.esize = sizeof(struct __rte_hash_rcu_dq_entry);
> +		params.free_fn = __hash_rcu_qsbr_free_resource;
> +		params.p = h;
> +		params.v = cfg->v;
> +		h->dq = rte_rcu_qsbr_dq_create(&params);
> +		if (h->dq == NULL) {
> +			rte_free(hash_rcu_cfg);
> +			RTE_LOG(ERR, HASH, "HASH defer queue creation failed\n");
> +			return 1;
> +		}
> 	} else {
> -		rte_ring_sp_enqueue_elem(h->free_slots,
> -				&bkt->key_idx[i], sizeof(uint32_t));
> +		rte_free(hash_rcu_cfg);
> +		rte_errno = EINVAL;
> +		return 1;
> +	}
> +
> +	hash_rcu_cfg->v = cfg->v;
> +	hash_rcu_cfg->mode = cfg->mode;
> +	hash_rcu_cfg->dq_size = cfg->dq_size;
> +	hash_rcu_cfg->reclaim_thd = cfg->reclaim_thd;
> +	hash_rcu_cfg->reclaim_max = cfg->reclaim_max;
> +	hash_rcu_cfg->free_key_data_func = cfg->free_key_data_func;
> +	hash_rcu_cfg->key_data_ptr = cfg->key_data_ptr;
> +
> +	h->hash_rcu_cfg = hash_rcu_cfg;
> +
> +	return 0;
> +}
> +
> +static inline void
> +remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
> +{
> +	int ret = free_slot(h, bkt->key_idx[i]);
> +	if (ret < 0) {
> +		RTE_LOG(ERR, HASH,
> +			"%s: could not enqueue free slots in global ring\n",
> +				__func__);
> 	}
> }
> 
> @@ -1521,6 +1680,8 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> 	int pos;
> 	int32_t ret, i;
> 	uint16_t short_sig;
> +	uint32_t index = EMPTY_SLOT;
> +	struct __rte_hash_rcu_dq_entry rcu_dq_entry;
> 
> 	short_sig = get_short_sig(sig);
> 	prim_bucket_idx = get_prim_bucket_index(h, sig);
> @@ -1555,10 +1716,9 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> 
> /* Search last bucket to see if empty to be recycled */
> return_bkt:
> -	if (!last_bkt) {
> -		__hash_rw_writer_unlock(h);
> -		return ret;
> -	}
> +	if (!last_bkt)
> +		goto return_key;
> +
> 	while (last_bkt->next) {
> 		prev_bkt = last_bkt;
> 		last_bkt = last_bkt->next;
> @@ -1571,11 +1731,11 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> 	/* found empty bucket and recycle */
> 	if (i == RTE_HASH_BUCKET_ENTRIES) {
> 		prev_bkt->next = NULL;
> -		uint32_t index = last_bkt - h->buckets_ext + 1;
> +		index = last_bkt - h->buckets_ext + 1;
> 		/* Recycle the empty bkt if
> 		 * no_free_on_del is disabled.
> 		 */
> -		if (h->no_free_on_del)
> +		if (h->no_free_on_del) {
> 			/* Store index of an empty ext bkt to be recycled
> 			 * on calling rte_hash_del_xxx APIs.
> 			 * When lock free read-write concurrency is enabled,
> @@ -1583,12 +1743,32 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> 			 * immediately (as readers might be using it still).
> 			 * Hence freeing of the ext bkt is piggy-backed to
> 			 * freeing of the key index.
> +			 * If using external RCU, store this index in an array.
> 			 */
> -			h->ext_bkt_to_free[ret] = index;
> -		else
> +			if (h->hash_rcu_cfg->v == NULL)
> +				h->ext_bkt_to_free[ret] = index;
> +		} else
> 			rte_ring_sp_enqueue_elem(h->free_ext_bkts, &index,
> 							sizeof(uint32_t));
> 	}
> +
> +return_key:
> +	/* Using internal RCU QSBR */
> +	if (h->hash_rcu_cfg->v) {
> +		/* Key index where key is stored, adding the first dummy index */
> +		rcu_dq_entry.key_idx = ret + 1;
> +		rcu_dq_entry.ext_bkt_idx = index;
> +		if (h->hash_rcu_cfg->mode == RTE_HASH_QSBR_MODE_SYNC) {
> +			/* Wait for quiescent state change. */
> +			rte_rcu_qsbr_synchronize(h->hash_rcu_cfg->v,
> +						 RTE_QSBR_THRID_INVALID);
> +			__hash_rcu_qsbr_free_resource((void *)((uintptr_t)h),
> +						      &rcu_dq_entry, 1);
> +		} else if (h->hash_rcu_cfg->mode == RTE_HASH_QSBR_MODE_DQ)
> +			/* Push into QSBR FIFO. */
> +			if (rte_rcu_qsbr_dq_enqueue(h->dq, &rcu_dq_entry) != 0)
> +				RTE_LOG(ERR, HASH, "Failed to push QSBR FIFO\n");
> +	}
> 	__hash_rw_writer_unlock(h);
> 	return ret;
> }
> @@ -1637,8 +1817,6 @@ rte_hash_free_key_with_position(const struct rte_hash *h,
> 
> 	RETURN_IF_TRUE(((h == NULL) || (key_idx == EMPTY_SLOT)), -EINVAL);
> 
> -	unsigned int lcore_id, n_slots;
> -	struct lcore_cache *cached_free_slots;
> 	const uint32_t total_entries = h->use_local_cache ?
> 		h->entries + (RTE_MAX_LCORE - 1) * (LCORE_CACHE_SIZE - 1) + 1
> 							: h->entries + 1;
> @@ -1656,28 +1834,9 @@ rte_hash_free_key_with_position(const struct rte_hash *h,
> 		}
> 	}
> 
> -	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_elem(h->free_slots,
> -						cached_free_slots->objs,
> -						sizeof(uint32_t),
> -						LCORE_CACHE_SIZE, NULL);
> -			RETURN_IF_TRUE((n_slots == 0), -EFAULT);
> -			cached_free_slots->len -= n_slots;
> -		}
> -		/* Put index of new free slot in cache. */
> -		cached_free_slots->objs[cached_free_slots->len] = key_idx;
> -		cached_free_slots->len++;
> -	} else {
> -		rte_ring_sp_enqueue_elem(h->free_slots, &key_idx,
> -						sizeof(uint32_t));
> -	}
> +	/* Enqueue slot to cache/ring of free slots. */
> +	return free_slot(h, key_idx);
> 
> -	return 0;
> }
> 
> static inline void
> diff --git a/lib/librte_hash/rte_cuckoo_hash.h b/lib/librte_hash/rte_cuckoo_hash.h
> index 345de6bf9cfd..85be49d3bbe7 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.h
> +++ b/lib/librte_hash/rte_cuckoo_hash.h
> @@ -168,6 +168,11 @@ struct rte_hash {
> 	struct lcore_cache *local_free_slots;
> 	/**< Local cache per lcore, storing some indexes of the free slots */
> 
> +	/* RCU config */
> +	struct rte_hash_rcu_config *hash_rcu_cfg;
> +	/**< HASH RCU QSBR configuration structure */
> +	struct rte_rcu_qsbr_dq *dq;	/**< RCU QSBR defer queue. */
> +
> 	/* Fields used in lookup */
> 
> 	uint32_t key_len __rte_cache_aligned;
> @@ -230,4 +235,7 @@ struct queue_node {
> 	int prev_slot;               /* Parent(slot) in search path */
> };
> 
> +/** @internal Default RCU defer queue entries to reclaim in one go. */
> +#define RTE_HASH_RCU_DQ_RECLAIM_MAX	16
> +
> #endif
> diff --git a/lib/librte_hash/rte_hash.h b/lib/librte_hash/rte_hash.h
> index bff40251bc98..5431bcf4aeb1 100644
> --- a/lib/librte_hash/rte_hash.h
> +++ b/lib/librte_hash/rte_hash.h
> @@ -15,6 +15,7 @@
> #include <stddef.h>
> 
> #include <rte_compat.h>
> +#include <rte_rcu_qsbr.h>
> 
> #ifdef __cplusplus
> extern "C" {
> @@ -45,7 +46,8 @@ extern "C" {
> /** 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.
> + * is enabled. However, if internal RCU is enabled, freeing of internal
> + * memory/index is done on delete
>  */
> #define RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL 0x10
> 
> @@ -67,6 +69,13 @@ typedef uint32_t (*rte_hash_function)(const void *key, uint32_t key_len,
> /** Type of function used to compare the hash key. */
> typedef int (*rte_hash_cmp_eq_t)(const void *key1, const void *key2, size_t key_len);
> 
> +/**
> + * Type of function used to free data stored in the key.
> + * Required when using internal RCU to allow application to free key-data once
> + * the key is returned to the the ring of free key-slots.
> + */
> +typedef void (*rte_hash_free_key_data)(void *p, void *key_data);
> +
> /**
>  * Parameters used when creating the hash table.
>  */
> @@ -81,6 +90,39 @@ struct rte_hash_parameters {
> 	uint8_t extra_flag;		/**< Indicate if additional parameters are present. */
> };
> 
> +/** RCU reclamation modes */
> +enum rte_hash_qsbr_mode {
> +	/** Create defer queue for reclaim. */
> +	RTE_HASH_QSBR_MODE_DQ = 0,
> +	/** Use blocking mode reclaim. No defer queue created. */
> +	RTE_HASH_QSBR_MODE_SYNC
> +};
> +
> +/** HASH RCU QSBR configuration structure. */
> +struct rte_hash_rcu_config {
> +	struct rte_rcu_qsbr *v;		/**< RCU QSBR variable. */
> +	enum rte_hash_qsbr_mode mode;
> +	/**< Mode of RCU QSBR. RTE_HASH_QSBR_MODE_xxx
> +	 * '0' for default: create defer queue for reclaim.
> +	 */
> +	uint32_t dq_size;
> +	/**< RCU defer queue size.
> +	 * default: total hash table entries.
> +	 */
> +	uint32_t reclaim_thd;	/**< Threshold to trigger auto reclaim. */
> +	uint32_t reclaim_max;
> +	/**< Max entries to reclaim in one go.
> +	 * default: RTE_HASH_RCU_DQ_RECLAIM_MAX.
> +	 */
> +	void *key_data_ptr;
> +	/**< Pointer passed to the free function. Typically, this is the
> +	 * pointer to the data structure to which the resource to free
> +	 * (key-data) belongs. This can be NULL.
> +	 */
> +	rte_hash_free_key_data free_key_data_func;
> +	/**< Function to call to free the resource (key-data). */
> +};
> +
> /** @internal A hash table structure. */
> struct rte_hash;
> 
> @@ -287,7 +329,8 @@ rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key, hash_sig_t
>  * 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,
> + * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled and
> + * internal RCU is NOT 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.
> @@ -316,7 +359,8 @@ rte_hash_del_key(const struct rte_hash *h, const void *key);
>  * 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,
> + * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled and
> + * internal RCU is NOT 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.
> @@ -370,7 +414,8 @@ rte_hash_get_key_with_position(const struct rte_hash *h, const int32_t position,
>  * 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,
> + * RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF is enabled and
> + * internal RCU is NOT 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.
> @@ -625,6 +670,28 @@ rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
>  */
> int32_t
> rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32_t *next);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Associate RCU QSBR variable with an Hash object.
> + *
> + * @param h
> + *   the hash object to add RCU QSBR
> + * @param cfg
> + *   RCU QSBR configuration
> + * @return
> + *   On success - 0
> + *   On error - 1 with error code set in rte_errno.
> + *   Possible rte_errno codes are:
> + *   - EINVAL - invalid pointer
> + *   - EEXIST - already added QSBR
> + *   - ENOMEM - memory allocation failure
> + */
> +__rte_experimental
> +int rte_hash_rcu_qsbr_add(struct rte_hash *h,
> +				struct rte_hash_rcu_config *cfg);
> #ifdef __cplusplus
> }
> #endif
> diff --git a/lib/librte_hash/rte_hash_version.map b/lib/librte_hash/rte_hash_version.map
> index c0db81014ff9..c6d73080f478 100644
> --- a/lib/librte_hash/rte_hash_version.map
> +++ b/lib/librte_hash/rte_hash_version.map
> @@ -36,5 +36,5 @@ EXPERIMENTAL {
> 	rte_hash_lookup_with_hash_bulk;
> 	rte_hash_lookup_with_hash_bulk_data;
> 	rte_hash_max_key_id;
> -
> +	rte_hash_rcu_qsbr_add;
> };
> -- 
> 2.17.1
>