[dpdk-dev] [PATCH v3 10/15] vhost: optimize enqueue function of packed ring

[Tiwei Bie]

On Thu, Sep 26, 2019 at 01:13:24AM +0800, Marvin Liu wrote:
>  static __rte_noinline uint32_t
>  virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
>  	struct rte_mbuf **pkts, uint32_t count)
>  {
>  	uint32_t pkt_idx = 0;
> -	uint16_t num_buffers;
> -	struct buf_vector buf_vec[BUF_VECTOR_MAX];
> -
> -	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
> -		uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
> -		uint16_t nr_vec = 0;
> -		uint16_t nr_descs = 0;
> -
> -		if (unlikely(reserve_avail_buf_packed(dev, vq,
> -						pkt_len, buf_vec, &nr_vec,
> -						&num_buffers, &nr_descs) < 0)) {
> -			VHOST_LOG_DEBUG(VHOST_DATA,
> -				"(%d) failed to get enough desc from vring\n",
> -				dev->vid);
> -			vq->shadow_used_idx -= num_buffers;
> -			break;
> +	uint32_t remained = count;
> +
> +	do {
> +		rte_prefetch0(&vq->desc_packed[vq->last_avail_idx &
> +			(vq->size - 1)]);

You can't assume packed ring size is a power of 2.