On Thu, Mar 03, 2016 at 05:40:14PM +0000, Xie, Huawei wrote:
> On 2/18/2016 9:48 PM, Yuanhan Liu wrote:
> > The current rte_vhost_dequeue_burst() implementation is a bit messy
> [...]
> > +
> > uint16_t
> > rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
> > struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
> > {
> > - struct rte_mbuf *m, *prev;
> > struct vhost_virtqueue *vq;
> > - struct vring_desc *desc;
> > - uint64_t vb_addr = 0;
> > - uint64_t vb_net_hdr_addr = 0;
> > - uint32_t head[MAX_PKT_BURST];
> > + uint32_t desc_indexes[MAX_PKT_BURST];
>
> indices
http://dictionary.reference.com/browse/index
index
noun, plural indexes, indices
>
>
> > uint32_t used_idx;
> > uint32_t i;
> > - uint16_t free_entries, entry_success = 0;
> > + uint16_t free_entries;
> > uint16_t avail_idx;
> > - struct virtio_net_hdr *hdr = NULL;
> > + struct rte_mbuf *m;
> >
> > if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->virt_qp_nb))) {
> > RTE_LOG(ERR, VHOST_DATA,
> > @@ -730,197 +813,49 @@ rte_vhost_dequeue_burst(struct virtio_net *dev,
> > uint16_t queue_id,
> > return 0;
> >
> > - if (entry_success < (free_entries - 1)) {
> > - /* Prefetch descriptor index. */
> > - rte_prefetch0(&vq->desc[head[entry_success+1]]);
> > - rte_prefetch0(&vq->used->ring[(used_idx + 1) &
> > (vq->size - 1)]);
> > - }
>
> Why is this prefetch silently dropped in the patch?
Oops, good catching. Will fix it. Thanks.
> > break;
> > + pkts[i] = m;
> >
> > - m->nb_segs = seg_num;
> > - if ((hdr->flags != 0) || (hdr->gso_type !=
> > VIRTIO_NET_HDR_GSO_NONE))
> > - vhost_dequeue_offload(hdr, m);
> > -
> > - pkts[entry_success] = m;
> > - vq->last_used_idx++;
> > - entry_success++;
> > + used_idx = vq->last_used_idx++ & (vq->size - 1);
> > + vq->used->ring[used_idx].id = desc_indexes[i];
> > + vq->used->ring[used_idx].len = 0;
>
> What is the correct value for ring[used_idx].len, the packet length or 0?
Good question. I didn't notice that before. Sounds buggy to me. However,
that's from the old code. Will check it.
--yliu
