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....@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
