RE: [PATCH v4 1/3] ethdev: add API for buffer recycle mode

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Feifei Wang [mailto:feifei.wang2@arm.com]
> Sent: Thursday, 23 March 2023 11.43
> 

[...]

> +static inline uint16_t rte_eth_rx_descriptors_refill(uint16_t port_id,
> +		uint16_t queue_id, uint16_t nb)
> +{
> +	struct rte_eth_fp_ops *p;
> +	void *qd;
> +
> +#ifdef RTE_ETHDEV_DEBUG_RX
> +	if (port_id >= RTE_MAX_ETHPORTS ||
> +			queue_id >= RTE_MAX_QUEUES_PER_PORT) {
> +		RTE_ETHDEV_LOG(ERR,
> +			"Invalid port_id=%u or queue_id=%u\n",
> +			port_id, queue_id);
> +		rte_errno = ENODEV;
> +		return 0;
> +	}
> +#endif
> +
> +	p = &rte_eth_fp_ops[port_id];
> +	qd = p->rxq.data[queue_id];
> +
> +#ifdef RTE_ETHDEV_DEBUG_RX
> +	if (!rte_eth_dev_is_valid_port(port_id)) {
> +		RTE_ETHDEV_LOG(ERR, "Invalid Rx port_id=%u\n", port_id);
> +		rte_errno = ENODEV;
> +		return 0;
> +
> +	if (qd == NULL) {
> +		RTE_ETHDEV_LOG(ERR, "Invalid Rx queue_id=%u for port_id=%u\n",
> +			queue_id, port_id);
> +		rte_errno = ENODEV;
> +		return 0;
> +	}
> +#endif
> +
> +	if (!p->rx_descriptors_refill)

Compare to NULL instead: if (p->rx_descriptors_refill == NULL)

> +		return 0;
> +
> +	return p->rx_descriptors_refill(qd, nb);
> +}
> +
>  /**@{@name Rx hardware descriptor states
>   * @see rte_eth_rx_descriptor_status
>   */
> @@ -6483,6 +6597,122 @@ rte_eth_tx_buffer(uint16_t port_id, uint16_t queue_id,
>  	return rte_eth_tx_buffer_flush(port_id, queue_id, buffer);
>  }
> 
> +/**
> + * @internal
> + * Tx routine for rte_eth_dev_buf_recycle().
> + * Stash Tx used buffers into Rx buffer ring in buffer recycle mode.
> + *
> + * @note
> + * This API can only be called by rte_eth_dev_buf_recycle().
> + * After calling this API, rte_eth_rx_descriptors_refill() should be
> + * called to refill Rx ring descriptors.
> + *
> + * When this functionality is not implemented in the driver, the return
> + * buffer number is 0.
> + *
> + * @param port_id
> + *   The port identifier of the Ethernet device.
> + * @param queue_id
> + *   The index of the transmit queue.
> + *   The value must be in the range [0, nb_tx_queue - 1] previously supplied
> + *   to rte_eth_dev_configure().
> + * @param rxq_buf_recycle_info
> + *   A pointer to a structure of Rx queue buffer ring information in buffer
> + *   recycle mode.
> + *
> + * @return
> + *   The number buffers correct to be filled in the Rx buffer ring.
> + *   - ENODEV: bad port or queue (only if compiled with debug).
> + */
> +static inline uint16_t rte_eth_tx_buf_stash(uint16_t port_id, uint16_t
> queue_id,
> +		struct rte_eth_rxq_buf_recycle_info *rxq_buf_recycle_info)
> +{
> +	struct rte_eth_fp_ops *p;
> +	void *qd;
> +
> +#ifdef RTE_ETHDEV_DEBUG_TX
> +	if (port_id >= RTE_MAX_ETHPORTS ||
> +			queue_id >= RTE_MAX_QUEUES_PER_PORT) {
> +		RTE_ETHDEV_LOG(ERR,
> +			"Invalid port_id=%u or queue_id=%u\n",
> +			port_id, queue_id);
> +		rte_errno = ENODEV;
> +		return 0;
> +	}
> +#endif
> +
> +	p = &rte_eth_fp_ops[port_id];
> +	qd = p->txq.data[queue_id];
> +
> +#ifdef RTE_ETHDEV_DEBUG_TX
> +	if (!rte_eth_dev_is_valid_port(port_id)) {
> +		RTE_ETHDEV_LOG(ERR, "Invalid Tx port_id=%u\n", port_id);
> +		rte_errno = ENODEV;
> +		return 0;
> +
> +	if (qd == NULL) {
> +		RTE_ETHDEV_LOG(ERR, "Invalid Tx queue_id=%u for port_id=%u\n",
> +			queue_id, port_id);
> +		rte_erno = ENODEV;
> +		return 0;
> +	}
> +#endif
> +
> +	if (p->tx_buf_stash == NULL)
> +		return 0;
> +
> +	return p->tx_buf_stash(qd, rxq_buf_recycle_info);
> +}
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
> + *
> + * Buffer recycle mode can let Tx queue directly put used buffers into Rx
> buffer
> + * ring. This avoids freeing buffers into mempool and allocating buffers from
> + * mempool.
> + *
> + * @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 rxq_recycle_info
> + *   A pointer to a structure of type *rte_eth_txq_rearm_data* to be filled.
> + * @return
> + *   - (0) on success or no recycling buffer.
> + *   - (-EINVAL) rxq_recycle_info is NULL.
> + */
> +__rte_experimental
> +static inline int
> +rte_eth_dev_buf_recycle(uint16_t rx_port_id, uint16_t rx_queue_id,
> +		uint16_t tx_port_id, uint16_t tx_queue_id,
> +		struct rte_eth_rxq_buf_recycle_info *rxq_buf_recycle_info)
> +{
> +	/* The number of recycling buffers. */
> +	uint16_t nb_buf;
> +
> +	if (!rxq_buf_recycle_info)
> +		return -EINVAL;

Compare to NULL instead: if (rxq_buf_recycle_info == NULL)

Alternatively: Consider RTE_ASSERT() and require rxq_buf_recycle_info to be valid.

> +
> +	/* Stash Tx used buffers into Rx buffer ring */
> +	nb_buf = rte_eth_tx_buf_stash(tx_port_id, tx_queue_id,
> +				rxq_buf_recycle_info);
> +	/* If there are recycling buffers, refill Rx queue descriptors. */
> +	if (nb_buf)
> +		rte_eth_rx_descriptors_refill(rx_port_id, rx_queue_id,
> +					nb_buf);
> +
> +	return 0;
> +}
> +
>  /**
>   * @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..10f9d5cbe7 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 Stash Tx used buffers into RX ring in buffer recycle mode */
> +typedef uint16_t (*eth_tx_buf_stash_t)(void *txq,
> +		struct rte_eth_rxq_buf_recycle_info *rxq_buf_recycle_info);
> +
> +/** @internal Refill Rx descriptors in buffer recycle mode */
> +typedef uint16_t (*eth_rx_descriptors_refill_t)(void *rxq, uint16_t nb);
> +
>  /**
>   * @internal
>   * Structure used to hold opaque pointers to internal ethdev Rx/Tx
> @@ -90,6 +97,8 @@ 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 in buffer recycle mode */
> +	eth_rx_descriptors_refill_t rx_descriptors_refill;
>  	/** Rx queues data. */
>  	struct rte_ethdev_qdata rxq;
>  	uintptr_t reserved1[3];

In order to keep 64 B alignment, the reserved1 array must be reduced from 3 to 2.

> @@ -106,6 +115,8 @@ 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;
> +	/** Stash Tx used buffers into RX ring in buffer recycle mode */
> +	eth_tx_buf_stash_t tx_buf_stash;
>  	/** Tx queues data. */
>  	struct rte_ethdev_qdata txq;
>  	uintptr_t reserved2[3];

In order to keep 64 B alignment, the reserved2 array must be reduced from 3 to 2.

> diff --git a/lib/ethdev/version.map b/lib/ethdev/version.map
> index 357d1a88c0..8a4b1dac80 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_dev_buf_recycle;
> +	rte_eth_rx_queue_buf_recycle_info_get;
>  };
> 
>  INTERNAL {
> @@ -328,4 +332,6 @@ INTERNAL {
>  	rte_eth_representor_id_get;
>  	rte_eth_switch_domain_alloc;
>  	rte_eth_switch_domain_free;
> +	rte_eth_tx_buf_stash;
> +	rte_eth_rx_descriptors_refill;
>  };
> --
> 2.25.1
>