Re: [dpdk-dev] [PATCH] eal: added new api to only enqueue a packet in tx buffer

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

On 8/8/2019 1:28 PM, Nilanjan Sarkar wrote:
> This api is similar like api `rte_eth_tx_buffer` except it
> does not attempt to flush the buffer in case buffer is full.
> The advantage is that, this api does not need port id and
> queue id. In case port id and queue id are shared within threads
> then application can not buffer a packet until it gets access
> to port and queue. So this function segregate buffering
> job from flushing job and thus removes dependency on port and queue.

Hi Nilanjan,

Sorry, the patch seems missed because of the misleading module info in the patch
title, this is not an 'eal' patch but a 'ethdev' patch ...

Related to the API, it looks like target is to reduce the critical section which
looks reasonable to me.

A concern is related to the making this function inline, we are discussing
moving existing inline functions to regular functions, this may have performance
affect but if the drop is acceptable what about making this an ethdev API?

Thanks,
ferruh

> 
> Signed-off-by: Nilanjan Sarkar <nsarkar@sandvine.com>
> ---
>  lib/librte_ethdev/rte_ethdev.h | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
> index dc6596bc9..bd8b8fee4 100644
> --- a/lib/librte_ethdev/rte_ethdev.h
> +++ b/lib/librte_ethdev/rte_ethdev.h
> @@ -4569,6 +4569,35 @@ rte_eth_tx_buffer(uint16_t port_id, uint16_t queue_id,
>  	return rte_eth_tx_buffer_flush(port_id, queue_id, buffer);
>  }
>  
> +/**
> + * Buffer a single packet for future transmission on Tx buffer. This buffer
> + * can be sent to a port and queue of a NIC using rte_eth_tx_buffer_flush ()
> + * call.
> + *
> + * This function enqueues a packet to Tx buffer. In case there is no space
> + * in Tx buffer, this function fails.
> + * Tx buffer will be flushed using rte_eth_tx_buffer_flush () call. It is
> + * application's responsibility to flush the Tx buffer in regular interval.
> + *
> + * @param buffer
> + *  Buffer used to collect packets to be sent.
> + * @param tx_pkt
> + *  Pointer to the packet mbuf to be sent.
> + * @return
> + *  0 = packet has been buffered for later transmission
> + *  -1 = Packet can not be buffered since it reached limit
> + */
> +static __rte_always_inline int
> +rte_eth_tx_enqueue(struct rte_eth_dev_tx_buffer *buffer, struct rte_mbuf *tx_pkt)
> +{
> +	if (buffer->length < buffer->size) {
> +		buffer->pkts[buffer->length++] = tx_pkt;
> +		return 0;
> +	}
> +
> +	return -1;
> +}
> +
>  #ifdef __cplusplus
>  }
>  #endif
>