On 2/18/2016 9:48 PM, Yuanhan Liu wrote:
> Current virtio_dev_merge_rx() implementation just looks like the
> old rte_vhost_dequeue_burst(), full of twisted logic, that you
> can see same code block in quite many different places.
>
> However, the logic of virtio_dev_merge_rx() is quite similar to
> virtio_dev_rx(). The big difference is that the mergeable one
> could allocate more than one available entries to hold the data.
> Fetching all available entries to vec_buf at once makes the
[...]
> - }
> +static inline uint32_t __attribute__((always_inline))
> +copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue
> *vq,
> + uint16_t res_start_idx, uint16_t res_end_idx,
> + struct rte_mbuf *m)
> +{
> + struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
> + uint32_t vec_idx = 0;
> + uint16_t cur_idx = res_start_idx;
> + uint64_t desc_addr;
> + uint32_t mbuf_offset, mbuf_avail;
> + uint32_t desc_offset, desc_avail;
> + uint32_t cpy_len;
> + uint16_t desc_idx, used_idx;
> + uint32_t nr_used = 0;
>
> - cpy_len = RTE_MIN(vb_avail, seg_avail);
> + if (m == NULL)
> + return 0;
Is this inherited from old code? Let us remove the unnecessary check.
Caller ensures it is not NULL.
>
> - while (cpy_len > 0) {
> - /* Copy mbuf data to vring buffer */
> - rte_memcpy((void *)(uintptr_t)(vb_addr + vb_offset),
> - rte_pktmbuf_mtod_offset(pkt, const void *, seg_offset),
> - cpy_len);
> + LOG_DEBUG(VHOST_DATA,
> + "(%"PRIu64") Current Index %d| End Index %d\n",
> + dev->device_fh, cur_idx, res_end_idx);
>
> - PRINT_PACKET(dev,
> - (uintptr_t)(vb_addr + vb_offset),
> - cpy_len, 0);
> + desc_addr = gpa_to_vva(dev, vq->buf_vec[vec_idx].buf_addr);
> + rte_prefetch0((void *)(uintptr_t)desc_addr);
> +
> + virtio_hdr.num_buffers = res_end_idx - res_start_idx;
> + LOG_DEBUG(VHOST_DATA, "(%"PRIu64") RX: Num merge buffers %d\n",
> + dev->device_fh, virtio_hdr.num_buffers);
>
> - seg_offset += cpy_len;
> - vb_offset += cpy_len;
> - seg_avail -= cpy_len;
> - vb_avail -= cpy_len;
> - entry_len += cpy_len;
> -
> - if (seg_avail != 0) {
> - /*
> - * The virtio buffer in this vring
> - * entry reach to its end.
> - * But the segment doesn't complete.
> - */
> - if ((vq->desc[vq->buf_vec[vec_idx].desc_idx].flags &
> - VRING_DESC_F_NEXT) == 0) {
> + virtio_enqueue_offload(m, &virtio_hdr.hdr);
> + rte_memcpy((void *)(uintptr_t)desc_addr,
> + (const void *)&virtio_hdr, vq->vhost_hlen);
> + PRINT_PACKET(dev, (uintptr_t)desc_addr, vq->vhost_hlen, 0);
> +
> + desc_avail = vq->buf_vec[vec_idx].buf_len - vq->vhost_hlen;
> + desc_offset = vq->vhost_hlen;
As we know we are in merge-able path, use sizeof(virtio_net_hdr) to save
one load for the header len.
> +
> + mbuf_avail = rte_pktmbuf_data_len(m);
> + mbuf_offset = 0;
> + while (1) {
> + /* done with current desc buf, get the next one */
> +
[...]
> + if (reserve_avail_buf_mergeable(vq, pkt_len, &start, &end) < 0)
> + break;
>
> + nr_used = copy_mbuf_to_desc_mergeable(dev, vq, start, end,
> + pkts[pkt_idx]);
In which case couldn't we get nr_used from start and end?
> rte_compiler_barrier();
>
> /*
> * Wait until it's our turn to add our buffer
> * to the used ring.
> */
> - while (unlikely(vq->last_used_idx != res_base_idx))
> + while (unlikely(vq->last_used_idx != start))
> rte_pause();
>
> - *(volatile uint16_t *)&vq->used->idx += entry_success;
> - vq->last_used_idx = res_cur_idx;
> + *(volatile uint16_t *)&vq->used->idx += nr_used;
> + vq->last_used_idx = end;
> }
>
> -merge_rx_exit:
> if (likely(pkt_idx)) {
> /* flush used->idx update before we read avail->flags. */
> rte_mb();
