Re: [dpdk-dev] [PATCH v3 7/7] virtio: pick simple rx/tx func

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 10/22/2015 10:45 AM, Jianfeng wrote:

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Huawei Xie
> Sent: Tuesday, October 20, 2015 11:30 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v3 7/7] virtio: pick simple rx/tx func
> 
> simple rx/tx func is enabled when user specifies single segment and no
> offload support.
> merge-able should be disabled to use simple rxtx.
> 
> Signed-off-by: Huawei Xie <huawei.xie@intel.com>
> ---
>  drivers/net/virtio/virtio_rxtx.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 947fc46..71f8cd4 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -62,6 +62,10 @@
>  #define  VIRTIO_DUMP_PACKET(m, len) do { } while (0)  #endif
> 
> +
> +#define VIRTIO_SIMPLE_FLAGS ((uint32_t)ETH_TXQ_FLAGS_NOMULTSEGS
> | \
> +	ETH_TXQ_FLAGS_NOOFFLOADS)
> +
>  static int use_simple_rxtx;
> 
>  static void
> @@ -471,6 +475,14 @@ virtio_dev_tx_queue_setup(struct rte_eth_dev
> *dev,
>  		return -EINVAL;
>  	}
> 
> +	/* Use simple rx/tx func if single segment and no offloads */
> +	if ((tx_conf->txq_flags & VIRTIO_SIMPLE_FLAGS) ==
> VIRTIO_SIMPLE_FLAGS) {
> +		PMD_INIT_LOG(INFO, "Using simple rx/tx path");
> +		dev->tx_pkt_burst = virtio_xmit_pkts_simple;
> +		dev->rx_pkt_burst = virtio_recv_pkts_vec;

Whether recv side mergeable is supported is controlled by virtio_negotiate_feature().
So "dev->rx_pkt_burst = virtio_recv_pkts_vec" should be restricted by 
hw->guest_features & VIRTIO_NET_F_MRG_RXBUF, right?

> +		use_simple_rxtx = 1;
> +	}
> +
>  	ret = virtio_dev_queue_setup(dev, VTNET_TQ, queue_idx,
> vtpci_queue_idx,
>  			nb_desc, socket_id, &vq);
>  	if (ret < 0) {
> --
> 1.8.1.4