Re: [dpdk-dev] [PATCH v4] mlx5: Support for rte_eth_rx_queue_count

[Shahaf Shuler <shahafs@mellanox.com>]

Hi Tom,

Adding ethdev maintainers and Oliver as the author of the new API. 


Saturday, October 27, 2018 6:11 PM, Tom Barbette:
> Subject: [PATCH v4] mlx5: Support for rte_eth_rx_queue_count
> 

I have a more basic question.
The rte_eth_rx_queue_count is a very old API, more or less from the beginning of DPDK. 
We progressed from then and a newer API to check the descriptor status was introduced @DPDK17.05 : rte_eth_rx_descriptor_status, see commit[1].
There is also a plan to deprecate it once all drivers will support the new API.

With the new API you can check the number of available descriptors on a similar way. 
So my question is, is the new API enough for your functionality? If not, what it is missing? I would prefer to improve the new one instead of starting to support the old one. 


[1]
commit b1b700ce7d6fe0db9152f73e8e00394fc2756e60                            
Author: Olivier Matz <olivier.matz@6wind.com>                              
Date:   Wed Mar 29 10:36:28 2017 +0200                                     
                                                                           
    ethdev: add descriptor status API                                      
                                                                           
    Introduce a new API to get the status of a descriptor.                 
                                                                           
    For Rx, it is almost similar to rx_descriptor_done API, except it      
    differentiates "used" descriptors (which are hold by the driver and not
    returned to the hardware).                                             
                                                                           
    For Tx, it is a new API.                                               
                                                                           
    The descriptor_done() API, and probably the rx_queue_count() API could 
    be replaced by this new API as soon as it is implemented on all PMDs.  
                                                                           
    Signed-off-by: Olivier Matz <olivier.matz@6wind.com>                   
    Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>  

            
> This patch adds support for the rx_queue_count API in mlx5 driver
> 
> Changes in v2:
>   * Fixed styling issues
>   * Fix missing return
> 
> Changes in v3:
>   * Fix styling comments and checks as per Yongseok Koh
>     <yskoh@mellanox.com> comments. Thanks !
> 
> Changes in v4:
>   * Fix compiling issue because of a line that disappeared in v3
> 
> Signed-off-by: Tom Barbette <barbette@kth.se>
> ---
>  drivers/net/mlx5/mlx5.c      |  1 +
>  drivers/net/mlx5/mlx5_rxtx.c | 78
> ++++++++++++++++++++++++++++++++++++++------
>  drivers/net/mlx5/mlx5_rxtx.h |  1 +
>  3 files changed, 70 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c index
> ec63bc6..6fccadd 100644
> --- a/drivers/net/mlx5/mlx5.c
> +++ b/drivers/net/mlx5/mlx5.c
> @@ -375,6 +375,7 @@ const struct eth_dev_ops mlx5_dev_ops = {
>  	.filter_ctrl = mlx5_dev_filter_ctrl,
>  	.rx_descriptor_status = mlx5_rx_descriptor_status,
>  	.tx_descriptor_status = mlx5_tx_descriptor_status,
> +	.rx_queue_count = mlx5_rx_queue_count,
>  	.rx_queue_intr_enable = mlx5_rx_intr_enable,
>  	.rx_queue_intr_disable = mlx5_rx_intr_disable,
>  	.is_removed = mlx5_is_removed,
> diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
> index 2d14f8a..2126205 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.c
> +++ b/drivers/net/mlx5/mlx5_rxtx.c
> @@ -417,20 +417,17 @@ mlx5_tx_descriptor_status(void *tx_queue,
> uint16_t offset)  }
> 
>  /**
> - * DPDK callback to check the status of a rx descriptor.
> + * Internal function to compute the number of used descriptors in an RX
> + queue
>   *
> - * @param rx_queue
> - *   The rx queue.
> - * @param[in] offset
> - *   The index of the descriptor in the ring.
> + * @param rxq
> + *   The Rx queue.
>   *
>   * @return
> - *   The status of the tx descriptor.
> + *   The number of used rx descriptor.
>   */
> -int
> -mlx5_rx_descriptor_status(void *rx_queue, uint16_t offset)
> +static uint32_t
> +rx_queue_count(struct mlx5_rxq_data *rxq)
>  {
> -	struct mlx5_rxq_data *rxq = rx_queue;
>  	struct rxq_zip *zip = &rxq->zip;
>  	volatile struct mlx5_cqe *cqe;
>  	const unsigned int cqe_n = (1 << rxq->cqe_n); @@ -461,12 +458,73
> @@ mlx5_rx_descriptor_status(void *rx_queue, uint16_t offset)
>  		cqe = &(*rxq->cqes)[cq_ci & cqe_cnt];
>  	}
>  	used = RTE_MIN(used, (1U << rxq->elts_n) - 1);
> -	if (offset < used)
> +	return used;
> +}
> +
> +/**
> + * DPDK callback to check the status of a rx descriptor.
> + *
> + * @param rx_queue
> + *   The Rx queue.
> + * @param[in] offset
> + *   The index of the descriptor in the ring.
> + *
> + * @return
> + *   The status of the tx descriptor.
> + */
> +int
> +mlx5_rx_descriptor_status(void *rx_queue, uint16_t offset) {
> +	struct mlx5_rxq_data *rxq = rx_queue;
> +	struct mlx5_rxq_ctrl *rxq_ctrl =
> +			container_of(rxq, struct mlx5_rxq_ctrl, rxq);
> +	struct rte_eth_dev *dev = ETH_DEV(rxq_ctrl->priv);
> +
> +	if (dev->rx_pkt_burst != mlx5_rx_burst) {
> +		rte_errno = ENOTSUP;
> +		return -rte_errno;
> +	}
> +	if (offset >= (1 << rxq->elts_n)) {
> +		rte_errno = EINVAL;
> +		return -rte_errno;
> +	}
> +	if (offset < rx_queue_count(rxq))
>  		return RTE_ETH_RX_DESC_DONE;
>  	return RTE_ETH_RX_DESC_AVAIL;
>  }
> 
>  /**
> + * DPDK callback to get the number of used descriptors in a RX queue
> + *
> + * @param dev
> + *   Pointer to the device structure.
> + *
> + * @param rx_queue_id
> + *   The Rx queue.
> + *
> + * @return
> + *   The number of used rx descriptor.
> + *   -EINVAL if the queue is invalid
> + */
> +uint32_t
> +mlx5_rx_queue_count(struct rte_eth_dev *dev, uint16_t rx_queue_id) {
> +	struct priv *priv = dev->data->dev_private;
> +	struct mlx5_rxq_data *rxq;
> +
> +	if (dev->rx_pkt_burst != mlx5_rx_burst) {
> +		rte_errno = ENOTSUP;
> +		return -rte_errno;
> +	}
> +	rxq = (*priv->rxqs)[rx_queue_id];
> +	if (!rxq) {
> +		rte_errno = EINVAL;
> +		return -rte_errno;
> +	}
> +	return rx_queue_count(rxq);
> +}
> +
> +/**
>   * DPDK callback for TX.
>   *
>   * @param dpdk_txq
> diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
> index 48ed2b2..c82059b 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.h
> +++ b/drivers/net/mlx5/mlx5_rxtx.h
> @@ -345,6 +345,7 @@ uint16_t removed_rx_burst(void *dpdk_rxq, struct
> rte_mbuf **pkts,
>  			  uint16_t pkts_n);
>  int mlx5_rx_descriptor_status(void *rx_queue, uint16_t offset);  int
> mlx5_tx_descriptor_status(void *tx_queue, uint16_t offset);
> +uint32_t mlx5_rx_queue_count(struct rte_eth_dev *dev, uint16_t
> +rx_queue_id);
> 
>  /* Vectorized version of mlx5_rxtx.c */  int
> mlx5_check_raw_vec_tx_support(struct rte_eth_dev *dev);
> --
> 2.7.4