Re: [dpdk-dev] [PATCH v2 2/4] ethdev: Add in data rxtx callback support

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2015-02-13 15:39, John McNamara:
> From: Richardson, Bruce <bruce.richardson@intel.com>
> 
> Add in support for inline processing of packets inside the RX or
> TX call. For an RX callback, what happens is that we get a set of
> packets from the NIC and then pass them to a callback function, if
> configured, to allow additional processing to be done on them, e.g.
> filling in more mbuf fields, before passing back to the application.
> On TX, the packets are similarly post-processed before being handed
> to the NIC for transmission.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
[...]
> @@ -2390,7 +2445,17 @@ rte_eth_rx_burst(uint8_t port_id, uint16_t queue_id,
>  	struct rte_eth_dev *dev;
>  
>  	dev = &rte_eth_devices[port_id];
> -	return (*dev->rx_pkt_burst)(dev->data->rx_queues[queue_id], rx_pkts, nb_pkts);
> +	nb_pkts = (*dev->rx_pkt_burst)(dev->data->rx_queues[queue_id], rx_pkts,
> +			nb_pkts);
> +	struct rte_eth_rxtx_callback *cb = dev->rx_cbs[queue_id];
> +	if (unlikely(cb != NULL)) {
> +		do {
> +			nb_pkts = cb->fn(port_id, queue_id, rx_pkts, nb_pkts,
> +					cb->param);
> +			cb = cb->next;
> +		} while (cb != NULL);
> +	}
> +	return nb_pkts;
>  }
>  #endif
>  
> @@ -2517,6 +2582,14 @@ rte_eth_tx_burst(uint8_t port_id, uint16_t queue_id,
>  	struct rte_eth_dev *dev;
>  
>  	dev = &rte_eth_devices[port_id];
> +	struct rte_eth_rxtx_callback *cb = dev->tx_cbs[queue_id];
> +	if (unlikely(cb != NULL)) {
> +		do {
> +			nb_pkts = cb->fn(port_id, queue_id, tx_pkts, nb_pkts,
> +					cb->param);
> +			cb = cb->next;
> +		} while (cb != NULL);
> +	}
>  	return (*dev->tx_pkt_burst)(dev->data->tx_queues[queue_id], tx_pkts, nb_pkts);
>  }
>  #endif

We all know how much the performance of these functions are important.
So I wonder if we could reduce the impact of this change.
I don't like the build options but maybe it should be discussed.