[PATCH v6 1/4] ethdev: add API for mbufs recycle mode

[Feifei Wang <feifei.wang2@arm.com>]

Add 'rte_eth_recycle_rx_queue_info_get' and 'rte_eth_recycle_mbufs'
APIs to recycle used mbufs from a transmit queue of an Ethernet device,
and move these mbufs into a mbuf ring for a receive queue of an Ethernet
device. This can bypass mempool 'put/get' operations hence saving CPU
cycles.

For each recycling mbufs, the rte_eth_recycle_mbufs() function performs
the following operations:
- Copy used *rte_mbuf* buffer pointers from Tx mbuf ring into Rx mbuf
ring.
- Replenish the Rx descriptors with the recycling *rte_mbuf* mbufs freed
from the Tx mbuf ring.

Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Suggested-by: Ruifeng Wang <ruifeng.wang@arm.com>
Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
---
 doc/guides/rel_notes/release_23_07.rst |   7 +
 lib/ethdev/ethdev_driver.h             |  10 ++
 lib/ethdev/ethdev_private.c            |   2 +
 lib/ethdev/rte_ethdev.c                |  31 +++++
 lib/ethdev/rte_ethdev.h                | 182 +++++++++++++++++++++++++
 lib/ethdev/rte_ethdev_core.h           |  15 +-
 lib/ethdev/version.map                 |   4 +
 7 files changed, 249 insertions(+), 2 deletions(-)

diff --git a/doc/guides/rel_notes/release_23_07.rst b/doc/guides/rel_notes/release_23_07.rst
index a9b1293689..f279036cb9 100644
--- a/doc/guides/rel_notes/release_23_07.rst
+++ b/doc/guides/rel_notes/release_23_07.rst
@@ -55,6 +55,13 @@ New Features
      Also, make sure to start the actual text at the margin.
      =======================================================
 
+* **Add mbufs recycling support. **
+  Added ``rte_eth_recycle_rx_queue_info_get`` and ``rte_eth_recycle_mbufs``
+  APIs which allow the user to copy used mbufs from the Tx mbuf ring
+  into the Rx mbuf ring. This feature supports the case that the Rx Ethernet
+  device is different from the Tx Ethernet device with respective driver
+  callback functions in ``rte_eth_recycle_mbufs``.
+
 
 Removed Items
 -------------
diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
index 2c9d615fb5..c6723d5277 100644
--- a/lib/ethdev/ethdev_driver.h
+++ b/lib/ethdev/ethdev_driver.h
@@ -59,6 +59,10 @@ struct rte_eth_dev {
 	eth_rx_descriptor_status_t rx_descriptor_status;
 	/** Check the status of a Tx descriptor */
 	eth_tx_descriptor_status_t tx_descriptor_status;
+	/** Pointer to PMD transmit mbufs reuse function */
+	eth_recycle_tx_mbufs_reuse_t recycle_tx_mbufs_reuse;
+	/** Pointer to PMD receive descriptors refill function */
+	eth_recycle_rx_descriptors_refill_t recycle_rx_descriptors_refill;
 
 	/**
 	 * Device data that is shared between primary and secondary processes
@@ -504,6 +508,10 @@ typedef void (*eth_rxq_info_get_t)(struct rte_eth_dev *dev,
 typedef void (*eth_txq_info_get_t)(struct rte_eth_dev *dev,
 	uint16_t tx_queue_id, struct rte_eth_txq_info *qinfo);
 
+typedef void (*eth_recycle_rxq_info_get_t)(struct rte_eth_dev *dev,
+	uint16_t rx_queue_id,
+	struct rte_eth_recycle_rxq_info *recycle_rxq_info);
+
 typedef int (*eth_burst_mode_get_t)(struct rte_eth_dev *dev,
 	uint16_t queue_id, struct rte_eth_burst_mode *mode);
 
@@ -1247,6 +1255,8 @@ struct eth_dev_ops {
 	eth_rxq_info_get_t         rxq_info_get;
 	/** Retrieve Tx queue information */
 	eth_txq_info_get_t         txq_info_get;
+	/** Retrieve mbufs recycle Rx queue information */
+	eth_recycle_rxq_info_get_t recycle_rxq_info_get;
 	eth_burst_mode_get_t       rx_burst_mode_get; /**< Get Rx burst mode */
 	eth_burst_mode_get_t       tx_burst_mode_get; /**< Get Tx burst mode */
 	eth_fw_version_get_t       fw_version_get; /**< Get firmware version */
diff --git a/lib/ethdev/ethdev_private.c b/lib/ethdev/ethdev_private.c
index 14ec8c6ccf..f8ab64f195 100644
--- a/lib/ethdev/ethdev_private.c
+++ b/lib/ethdev/ethdev_private.c
@@ -277,6 +277,8 @@ eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
 	fpo->rx_queue_count = dev->rx_queue_count;
 	fpo->rx_descriptor_status = dev->rx_descriptor_status;
 	fpo->tx_descriptor_status = dev->tx_descriptor_status;
+	fpo->recycle_tx_mbufs_reuse = dev->recycle_tx_mbufs_reuse;
+	fpo->recycle_rx_descriptors_refill = dev->recycle_rx_descriptors_refill;
 
 	fpo->rxq.data = dev->data->rx_queues;
 	fpo->rxq.clbk = (void **)(uintptr_t)dev->post_rx_burst_cbs;
diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index 4d03255683..7c27dcfea4 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -5784,6 +5784,37 @@ rte_eth_tx_queue_info_get(uint16_t port_id, uint16_t queue_id,
 	return 0;
 }
 
+int
+rte_eth_recycle_rx_queue_info_get(uint16_t port_id, uint16_t queue_id,
+		struct rte_eth_recycle_rxq_info *recycle_rxq_info)
+{
+	struct rte_eth_dev *dev;
+
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
+	dev = &rte_eth_devices[port_id];
+
+	if (queue_id >= dev->data->nb_rx_queues) {
+		RTE_ETHDEV_LOG(ERR, "Invalid Rx queue_id=%u\n", queue_id);
+		return -EINVAL;
+	}
+
+	if (dev->data->rx_queues == NULL ||
+			dev->data->rx_queues[queue_id] == NULL) {
+		RTE_ETHDEV_LOG(ERR,
+			   "Rx queue %"PRIu16" of device with port_id=%"
+			   PRIu16" has not been setup\n",
+			   queue_id, port_id);
+		return -EINVAL;
+	}
+
+	if (*dev->dev_ops->recycle_rxq_info_get == NULL)
+		return -ENOTSUP;
+
+	dev->dev_ops->recycle_rxq_info_get(dev, queue_id, recycle_rxq_info);
+
+	return 0;
+}
+
 int
 rte_eth_rx_burst_mode_get(uint16_t port_id, uint16_t queue_id,
 			  struct rte_eth_burst_mode *mode)
diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
index 99fe9e238b..7434aa2483 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -1820,6 +1820,30 @@ struct rte_eth_txq_info {
 	uint8_t queue_state;        /**< one of RTE_ETH_QUEUE_STATE_*. */
 } __rte_cache_min_aligned;
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice.
+ *
+ * Ethernet device Rx queue information structure for recycling mbufs.
+ * Used to retrieve Rx queue information when Tx queue reusing mbufs and moving
+ * them into Rx mbuf ring.
+ */
+struct rte_eth_recycle_rxq_info {
+	struct rte_mbuf **mbuf_ring; /**< mbuf ring of Rx queue. */
+	struct rte_mempool *mp;     /**< mempool of Rx queue. */
+	uint16_t *refill_head;      /**< head of Rx queue refilling mbufs. */
+	uint16_t *receive_tail;     /**< tail of Rx queue receiving pkts. */
+	uint16_t mbuf_ring_size;     /**< configured number of mbuf ring size. */
+	/**
+	 * Requirement on mbuf refilling batch size of Rx mbuf ring.
+	 * For some PMD drivers, the number of Rx mbuf ring refilling mbufs
+	 * should be aligned with mbuf ring size, in order to simplify
+	 * ring wrapping around.
+	 * Value 0 means that PMD drivers have no requirement for this.
+	 */
+	uint16_t refill_requirement;
+} __rte_cache_min_aligned;
+
 /* Generic Burst mode flag definition, values can be ORed. */
 
 /**
@@ -4809,6 +4833,31 @@ int rte_eth_rx_queue_info_get(uint16_t port_id, uint16_t queue_id,
 int rte_eth_tx_queue_info_get(uint16_t port_id, uint16_t queue_id,
 	struct rte_eth_txq_info *qinfo);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Retrieve information about given ports's Rx queue for recycling mbufs.
+ *
+ * @param port_id
+ *   The port identifier of the Ethernet device.
+ * @param queue_id
+ *   The Rx queue on the Ethernet devicefor which information
+ *   will be retrieved.
+ * @param recycle_rxq_info
+ *   A pointer to a structure of type *rte_eth_recycle_rxq_info* to be filled.
+ *
+ * @return
+ *   - 0: Success
+ *   - -ENODEV:  If *port_id* is invalid.
+ *   - -ENOTSUP: routine is not supported by the device PMD.
+ *   - -EINVAL:  The queue_id is out of range.
+ */
+__rte_experimental
+int rte_eth_recycle_rx_queue_info_get(uint16_t port_id,
+		uint16_t queue_id,
+		struct rte_eth_recycle_rxq_info *recycle_rxq_info);
+
 /**
  * Retrieve information about the Rx packet burst mode.
  *
@@ -6483,6 +6532,139 @@ rte_eth_tx_buffer(uint16_t port_id, uint16_t queue_id,
 	return rte_eth_tx_buffer_flush(port_id, queue_id, buffer);
 }
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Recycle used mbufs from a transmit queue of an Ethernet device, and move
+ * these mbufs into a mbuf ring for a receive queue of an Ethernet device.
+ * This can bypass mempool path to save CPU cycles.
+ *
+ * The rte_eth_recycle_mbufs() function loops, with rte_eth_rx_burst() and
+ * rte_eth_tx_burst() functions, freeing Tx used mbufs and replenishing Rx
+ * descriptors. The number of recycling mbufs depends on the request of Rx mbuf
+ * ring, with the constraint of enough used mbufs from Tx mbuf ring.
+ *
+ * For each recycling mbufs, the rte_eth_recycle_mbufs() function performs the
+ * following operations:
+ *
+ * - Copy used *rte_mbuf* buffer pointers from Tx mbuf ring into Rx mbuf ring.
+ *
+ * - Replenish the Rx descriptors with the recycling *rte_mbuf* mbufs freed
+ *   from the Tx mbuf ring.
+ *
+ * This function spilts Rx and Tx path with different callback functions. The
+ * callback function recycle_tx_mbufs_reuse is for Tx driver. The callback
+ * function recycle_rx_descriptors_refill is for Rx driver. rte_eth_recycle_mbufs()
+ * can support the case that Rx Ethernet device is different from Tx Ethernet device.
+ *
+ * It is the responsibility of users to select the Rx/Tx queue pair to recycle
+ * mbufs. Before call this function, users must call rte_eth_recycle_rxq_info_get
+ * function to retrieve selected Rx queue information.
+ * @see rte_eth_recycle_rxq_info_get, struct rte_eth_recycle_rxq_info
+ *
+ * Currently, the rte_eth_recycle_mbufs() function can only support one-time pairing
+ * between the receive queue and transmit queue. Do not pair one receive queue with
+ * multiple transmit queues or pair one transmit queue with multiple receive queues,
+ * in order to avoid memory error rewriting.
+ *
+ * @param rx_port_id
+ *   Port identifying the receive side.
+ * @param rx_queue_id
+ *   The index of the receive queue identifying the receive side.
+ *   The value must be in the range [0, nb_rx_queue - 1] previously supplied
+ *   to rte_eth_dev_configure().
+ * @param tx_port_id
+ *   Port identifying the transmit side.
+ * @param tx_queue_id
+ *   The index of the transmit queue identifying the transmit side.
+ *   The value must be in the range [0, nb_tx_queue - 1] previously supplied
+ *   to rte_eth_dev_configure().
+ * @param recycle_rxq_info
+ *   A pointer to a structure of type *rte_eth_recycle_rxq_info* which contains
+ *   the information of the Rx queue mbuf ring.
+ * @return
+ *   The number of recycling mbufs.
+ */
+__rte_experimental
+static inline uint16_t
+rte_eth_recycle_mbufs(uint16_t rx_port_id, uint16_t rx_queue_id,
+		uint16_t tx_port_id, uint16_t tx_queue_id,
+		struct rte_eth_recycle_rxq_info *recycle_rxq_info)
+{
+	struct rte_eth_fp_ops *p;
+	void *qd;
+	uint16_t nb_mbufs;
+
+#ifdef RTE_ETHDEV_DEBUG_TX
+	if (tx_port_id >= RTE_MAX_ETHPORTS ||
+			tx_queue_id >= RTE_MAX_QUEUES_PER_PORT) {
+		RTE_ETHDEV_LOG(ERR,
+				"Invalid tx_port_id=%u or tx_queue_id=%u\n",
+				tx_port_id, tx_queue_id);
+		return 0;
+	}
+#endif
+
+	/* fetch pointer to queue data */
+	p = &rte_eth_fp_ops[tx_port_id];
+	qd = p->txq.data[tx_queue_id];
+
+#ifdef RTE_ETHDEV_DEBUG_TX
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(tx_port_id, 0);
+
+	if (qd == NULL) {
+		RTE_ETHDEV_LOG(ERR, "Invalid Tx queue_id=%u for port_id=%u\n",
+				tx_queue_id, tx_port_id);
+		return 0;
+	}
+#endif
+	if (p->recycle_tx_mbufs_reuse == NULL)
+		return 0;
+
+	/* Copy used *rte_mbuf* buffer pointers from Tx mbuf ring
+	 * into Rx mbuf ring.
+	 */
+	nb_mbufs = p->recycle_tx_mbufs_reuse(qd, recycle_rxq_info);
+
+	/* If no recycling mbufs, return 0. */
+	if (nb_mbufs == 0)
+		return 0;
+
+#ifdef RTE_ETHDEV_DEBUG_RX
+	if (rx_port_id >= RTE_MAX_ETHPORTS ||
+			rx_queue_id >= RTE_MAX_QUEUES_PER_PORT) {
+		RTE_ETHDEV_LOG(ERR, "Invalid rx_port_id=%u or rx_queue_id=%u\n",
+				rx_port_id, rx_queue_id);
+		return 0;
+	}
+#endif
+
+	/* fetch pointer to queue data */
+	p = &rte_eth_fp_ops[rx_port_id];
+	qd = p->rxq.data[rx_queue_id];
+
+#ifdef RTE_ETHDEV_DEBUG_RX
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(rx_port_id, 0);
+
+	if (qd == NULL) {
+		RTE_ETHDEV_LOG(ERR, "Invalid Rx queue_id=%u for port_id=%u\n",
+				rx_queue_id, rx_port_id);
+		return 0;
+	}
+#endif
+
+	if (p->recycle_rx_descriptors_refill == NULL)
+		return 0;
+
+	/* Replenish the Rx descriptors with the recycling
+	 * into Rx mbuf ring.
+	 */
+	p->recycle_rx_descriptors_refill(qd, nb_mbufs);
+
+	return nb_mbufs;
+}
+
 /**
  * @warning
  * @b EXPERIMENTAL: this API may change without prior notice
diff --git a/lib/ethdev/rte_ethdev_core.h b/lib/ethdev/rte_ethdev_core.h
index dcf8adab92..a2e6ea6b6c 100644
--- a/lib/ethdev/rte_ethdev_core.h
+++ b/lib/ethdev/rte_ethdev_core.h
@@ -56,6 +56,13 @@ typedef int (*eth_rx_descriptor_status_t)(void *rxq, uint16_t offset);
 /** @internal Check the status of a Tx descriptor */
 typedef int (*eth_tx_descriptor_status_t)(void *txq, uint16_t offset);
 
+/** @internal Copy used mbufs from Tx mbuf ring into Rx mbuf ring */
+typedef uint16_t (*eth_recycle_tx_mbufs_reuse_t)(void *txq,
+		struct rte_eth_recycle_rxq_info *recycle_rxq_info);
+
+/** @internal Refill Rx descriptors with the recycling mbufs */
+typedef void (*eth_recycle_rx_descriptors_refill_t)(void *rxq, uint16_t nb);
+
 /**
  * @internal
  * Structure used to hold opaque pointers to internal ethdev Rx/Tx
@@ -90,9 +97,11 @@ struct rte_eth_fp_ops {
 	eth_rx_queue_count_t rx_queue_count;
 	/** Check the status of a Rx descriptor. */
 	eth_rx_descriptor_status_t rx_descriptor_status;
+	/** Refill Rx descriptors with the recycling mbufs. */
+	eth_recycle_rx_descriptors_refill_t recycle_rx_descriptors_refill;
 	/** Rx queues data. */
 	struct rte_ethdev_qdata rxq;
-	uintptr_t reserved1[3];
+	uintptr_t reserved1[2];
 	/**@}*/
 
 	/**@{*/
@@ -106,9 +115,11 @@ struct rte_eth_fp_ops {
 	eth_tx_prep_t tx_pkt_prepare;
 	/** Check the status of a Tx descriptor. */
 	eth_tx_descriptor_status_t tx_descriptor_status;
+	/** Copy used mbufs from Tx mbuf ring into Rx. */
+	eth_recycle_tx_mbufs_reuse_t recycle_tx_mbufs_reuse;
 	/** Tx queues data. */
 	struct rte_ethdev_qdata txq;
-	uintptr_t reserved2[3];
+	uintptr_t reserved2[2];
 	/**@}*/
 
 } __rte_cache_aligned;
diff --git a/lib/ethdev/version.map b/lib/ethdev/version.map
index 357d1a88c0..45c417f6bd 100644
--- a/lib/ethdev/version.map
+++ b/lib/ethdev/version.map
@@ -299,6 +299,10 @@ EXPERIMENTAL {
 	rte_flow_action_handle_query_update;
 	rte_flow_async_action_handle_query_update;
 	rte_flow_async_create_by_index;
+
+	# added in 23.07
+	rte_eth_recycle_mbufs;
+	rte_eth_recycle_rx_queue_info_get;
 };
 
 INTERNAL {
-- 
2.25.1