Re: [dpdk-dev] [PATCH v2] ixgbe: don't override mbuf buffer length

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Dec 04, 2014 at 07:09:13PM +0100, Jean-Mickael Guerin wrote:
> The template mbuf_initializer is hard coded with a buflen which
> might have been set differently by the application at the time of
> mbuf pool creation.
> 
> Switch to a mbuf allocation, to fetch the correct default values.
> There is no performance impact because this is not a data-plane API.
> 
> Signed-off-by: Jean-Mickael Guerin <jean-mickael.guerin@6wind.com>
> Acked-by: David Marchand <david.marchand@6wind.com>
> Fixes: 0ff3324da2 ("ixgbe: rework vector pmd following mbuf changes")
> ---
While I realise the debate is still ongoing, this approach looks fine to me.

Acked-by: Bruce Richardson <bruce.richardson@intel.com>

> 
>  v2: check returned value of ixgbe_rxq_vec_setup
> 
>  lib/librte_pmd_ixgbe/ixgbe_rxtx.c     |  5 ++++-
>  lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 19 ++++++++++++-------
>  2 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> index 5c36bff..7994da1 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> @@ -2244,7 +2244,10 @@ ixgbe_dev_rx_queue_setup(struct rte_eth_dev *dev,
>  	use_def_burst_func = check_rx_burst_bulk_alloc_preconditions(rxq);
>  
>  #ifdef RTE_IXGBE_INC_VECTOR
> -	ixgbe_rxq_vec_setup(rxq);
> +	if (ixgbe_rxq_vec_setup(rxq) < 0) {
> +		ixgbe_rx_queue_release(rxq);
> +		return (-ENOMEM);
> +	}
>  #endif
>  	/* Check if pre-conditions are satisfied, and no Scattered Rx */
>  	if (!use_def_burst_func && !dev->data->scattered_rx) {
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> index c1b5a78..f7b02f5 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c
> @@ -732,17 +732,22 @@ static struct ixgbe_txq_ops vec_txq_ops = {
>  int
>  ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq)
>  {
> -	struct rte_mbuf mb_def = { .buf_addr = 0 }; /* zeroed mbuf */
> +	struct rte_mbuf *mb_def;
>  
> -	mb_def.nb_segs = 1;
> -	mb_def.data_off = RTE_PKTMBUF_HEADROOM;
> -	mb_def.buf_len = rxq->mb_pool->elt_size - sizeof(struct rte_mbuf);
> -	mb_def.port = rxq->port_id;
> -	rte_mbuf_refcnt_set(&mb_def, 1);
> +	mb_def = rte_pktmbuf_alloc(rxq->mb_pool);
> +	if (mb_def == NULL) {
> +		PMD_INIT_LOG(ERR, "ixgbe_rxq_vec_setup: could not allocate one mbuf");
> +		return -1;
> +	}
> +	/* nb_segs, refcnt, data_off and buf_len are already set */
> +	mb_def->port = rxq->port_id;
>  
>  	/* prevent compiler reordering: rearm_data covers previous fields */
>  	rte_compiler_barrier();
> -	rxq->mbuf_initializer = *((uint64_t *)&mb_def.rearm_data);
> +	rxq->mbuf_initializer = *((uint64_t *)&mb_def->rearm_data);
> +
> +	rte_pktmbuf_free(mb_def);
> +
>  	return 0;
>  }
>  
> -- 
> 2.1.3
>