On Mon, Mar 07, 2016 at 07:52:22AM +0000, Xie, Huawei wrote:

On 2/18/2016 9:48 PM, Yuanhan Liu wrote:

quoted

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

[...]

quoted

-	}
+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?

Yes.

Let us remove the unnecessary check.
Caller ensures it is not NULL.

...

quoted

+	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.

Please, it's a refactor patch series. You have mentioned quite many
trivial issues here and there, which I don't care too much and I don't
think they would matter somehow. In addition, they are actually from
the old code.

quoted

+
+	mbuf_avail  = rte_pktmbuf_data_len(m);
+	mbuf_offset = 0;
+	while (1) {
+		/* done with current desc buf, get the next one */
+

[...]

quoted

+		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?

When pkts[pkt_idx] is NULL, though you suggest to remove it, the check
is here.

	--yliu