Re: [dpdk-dev] [RFC PATCH v1 1/4] ethdev: add support for PMD-tuned Tx/Rx parameters

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/7/2018 12:08 PM, Remy Horton wrote:
> The optimal values of several transmission & reception related
> parameters, such as burst sizes, descriptor ring sizes, and number
> of queues, varies between different network interface devices. This
> patch allows individual PMDs to specify preferred parameter values.
> 
> Signed-off-by: Remy Horton <remy.horton@intel.com>
> ---
>  lib/librte_ether/rte_ethdev.c | 18 ++++++++++++++++++
>  lib/librte_ether/rte_ethdev.h | 15 +++++++++++++++

Can you please remove deprecation notice in this patch.

>  2 files changed, 33 insertions(+)
> 
> diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
> index 0590f0c..1630407 100644
> --- a/lib/librte_ether/rte_ethdev.c
> +++ b/lib/librte_ether/rte_ethdev.c
> @@ -1461,6 +1461,10 @@ rte_eth_rx_queue_setup(uint16_t port_id, uint16_t rx_queue_id,
>  		return -EINVAL;
>  	}
>  
> +	/* Use default specified by driver, if nb_rc_desc is zero */
> +	if (nb_rx_desc == 0)
> +		nb_rx_desc = dev_info.preferred_queue_values.rx_ring_size;
> +
>  	if (nb_rx_desc > dev_info.rx_desc_lim.nb_max ||
>  			nb_rx_desc < dev_info.rx_desc_lim.nb_min ||
>  			nb_rx_desc % dev_info.rx_desc_lim.nb_align != 0) {
> @@ -1584,6 +1588,10 @@ rte_eth_tx_queue_setup(uint16_t port_id, uint16_t tx_queue_id,
>  
>  	rte_eth_dev_info_get(port_id, &dev_info);
>  
> +	/* Use default specified by driver, if nb_tx_desc is zero */
> +	if (nb_tx_desc == 0)
> +		nb_tx_desc = dev_info.preferred_queue_values.tx_ring_size;
> +
>  	if (nb_tx_desc > dev_info.tx_desc_lim.nb_max ||
>  	    nb_tx_desc < dev_info.tx_desc_lim.nb_min ||
>  	    nb_tx_desc % dev_info.tx_desc_lim.nb_align != 0) {
> @@ -2394,6 +2402,16 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
>  	dev_info->rx_desc_lim = lim;
>  	dev_info->tx_desc_lim = lim;
>  
> +	/* Defaults for drivers that don't implement preferred
> +	 * queue parameters.
> +	 */
> +	dev_info->preferred_queue_values.rx_burst_size = 0;
> +	dev_info->preferred_queue_values.tx_burst_size = 0;
> +	dev_info->preferred_queue_values.nb_rx_queues = 1;
> +	dev_info->preferred_queue_values.nb_tx_queues = 1;
> +	dev_info->preferred_queue_values.rx_ring_size = 1024;
> +	dev_info->preferred_queue_values.tx_ring_size = 1024;


Not sure about having these defaults here. It is OK to have defaults in driver,
in application or in config file, but I am not sure if putting them into device
abstraction layer hides them.

What about not providing any default in ethdev layer, and get zero as invalid
when using them?

> +
>  	RTE_FUNC_PTR_OR_RET(*dev->dev_ops->dev_infos_get);
>  	(*dev->dev_ops->dev_infos_get)(dev, dev_info);
>  	dev_info->driver_name = dev->device->driver->name;
> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
> index 0361533..67ce82d 100644
> --- a/lib/librte_ether/rte_ethdev.h
> +++ b/lib/librte_ether/rte_ethdev.h
> @@ -988,6 +988,18 @@ struct rte_eth_conf {
>  
>  struct rte_pci_device;
>  
> +/*
> + * Preferred queue parameters.
> + */
> +struct rte_eth_dev_pref_queue_info {
> +	uint16_t rx_burst_size;
> +	uint16_t tx_burst_size;
> +	uint16_t rx_ring_size;
> +	uint16_t tx_ring_size;
> +	uint16_t nb_rx_queues;
> +	uint16_t nb_tx_queues;
> +};
> +
>  /**
>   * Ethernet device information
>   */
> @@ -1029,6 +1041,9 @@ struct rte_eth_dev_info {
>  	/** Configured number of rx/tx queues */
>  	uint16_t nb_rx_queues; /**< Number of RX queues. */
>  	uint16_t nb_tx_queues; /**< Number of TX queues. */
> +
> +	/** Queue size recommendations */

Not only queue size.

> +	struct rte_eth_dev_pref_queue_info preferred_queue_values;

Although these are queue related values, not per-queue but per-port, the
variable name "preferred_queue_values" gives the impression that these are per
queue. And "rx_burst_size" is not related to queue at all I think.

What do you think renaming structure and variable name, "preferred_dev_config"
perhaps?

>  };
>  
>  /**
>