[dpdk-dev] [PATCH 5/5] net/virtio: optimize xmit enqueue for packed ring

[Maxime Coquelin]

On 2/19/19 11:59 AM, Tiwei Bie wrote:
> This patch introduces an optimized enqueue function in packed
> ring for the case that virtio net header can be prepended to
> the unchained mbuf.
> 
> Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
> ---
>   drivers/net/virtio/virtio_rxtx.c | 63 +++++++++++++++++++++++++++++++-
>   1 file changed, 61 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 60fa3aa50..771d3c3f6 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -623,6 +623,62 @@ virtqueue_enqueue_xmit_inorder(struct virtnet_tx *txvq,
>   	vq->vq_desc_head_idx = idx & (vq->vq_nentries - 1);
>   }
>   
> +static inline void
> +virtqueue_enqueue_xmit_packed_fast(struct virtnet_tx *txvq,
> +				   struct rte_mbuf *cookie,
> +				   int in_order)
> +{
> +	struct virtqueue *vq = txvq->vq;
> +	struct vring_packed_desc *dp;
> +	struct vq_desc_extra *dxp;
> +	uint16_t idx, id, flags;
> +	uint16_t head_size = vq->hw->vtnet_hdr_size;
> +	struct virtio_net_hdr *hdr;
> +
> +	id = in_order ? vq->vq_avail_idx : vq->vq_desc_head_idx;
> +	idx = vq->vq_avail_idx;
> +	dp = &vq->ring_packed.desc_packed[idx];
> +
> +	dxp = &vq->vq_descx[id];
> +	dxp->ndescs = 1;
> +	dxp->cookie = cookie;
> +
> +	flags = vq->avail_used_flags;
> +
> +	/* prepend cannot fail, checked by caller */
> +	hdr = (struct virtio_net_hdr *)
> +		rte_pktmbuf_prepend(cookie, head_size);
> +	cookie->pkt_len -= head_size;
> +
> +	/* if offload disabled, hdr is not zeroed yet, do it now */
> +	if (!vq->hw->has_tx_offload)
> +		virtqueue_clear_net_hdr(hdr);
> +	else
> +		virtqueue_xmit_offload(hdr, cookie, true);
> +
> +	dp->addr = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq);
> +	dp->len  = cookie->data_len;
> +	dp->id   = id;
> +
> +	if (++vq->vq_avail_idx >= vq->vq_nentries) {
> +		vq->vq_avail_idx -= vq->vq_nentries;
> +		vq->avail_wrap_counter ^= 1;
> +		vq->avail_used_flags ^=
> +			VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
> +	}
> +
> +	vq->vq_free_cnt--;
> +
> +	if (!in_order) {
> +		vq->vq_desc_head_idx = dxp->next;
> +		if (vq->vq_desc_head_idx == VQ_RING_DESC_CHAIN_END)
> +			vq->vq_desc_tail_idx = VQ_RING_DESC_CHAIN_END;
> +	}
> +
> +	virtio_wmb(vq->hw->weak_barriers);
> +	dp->flags = flags;
> +}
> +
>   static inline void
>   virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
>   			      uint16_t needed, int can_push, int in_order)
> @@ -1979,8 +2035,11 @@ virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf **tx_pkts,
>   		}
>   
>   		/* Enqueue Packet buffers */
> -		virtqueue_enqueue_xmit_packed(txvq, txm, slots, can_push,
> -					      in_order);
> +		if (can_push)
> +			virtqueue_enqueue_xmit_packed_fast(txvq, txm, in_order);
> +		else
> +			virtqueue_enqueue_xmit_packed(txvq, txm, slots, 0,
> +						      in_order);
>   
>   		virtio_update_packet_stats(&txvq->stats, txm);
>   	}
> 

I like this patch, but shouldn't virtqueue_enqueue_xmit_packed() be
simplified to get rid off "can_push" now that this case as a dedicated
function?

Regards,
Maxime