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

Tiwei Bie tiwei.bie at intel.com
Thu Feb 21 13:25:57 CET 2019


On Thu, Feb 21, 2019 at 12:22:29PM +0100, Maxime Coquelin wrote:
> 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?

Yeah, I had the same thought. But after a second thought, I
think we may also want to push the net hdr to the mbuf even
if its nb_segs isn't 1 in the future, so I left it untouched.

Thanks,
Tiwei


More information about the dev mailing list