vhost: simplify descriptor buffer prefetching

Now that we have a single function to map the descriptors
buffers, let's prefetch them there as it is the earliest
place we can do it.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 50aeaa0..5b85b83 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -286,6 +286,8 @@ map_one_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
                if (unlikely(!desc_addr))
                        return -1;
 
+               rte_prefetch0((void *)(uintptr_t)desc_addr);
+
                buf_vec[vec_id].buf_iova = desc_iova;
                buf_vec[vec_id].buf_addr = desc_addr;
                buf_vec[vec_id].buf_len  = desc_chunck_len;
@@ -666,9 +668,6 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
        buf_iova = buf_vec[vec_idx].buf_iova;
        buf_len = buf_vec[vec_idx].buf_len;
 
-       if (nr_vec > 1)
-               rte_prefetch0((void *)(uintptr_t)buf_vec[1].buf_addr);
-
        if (unlikely(buf_len < dev->vhost_hlen && nr_vec <= 1)) {
                error = -1;
                goto out;
@@ -711,10 +710,6 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        buf_iova = buf_vec[vec_idx].buf_iova;
                        buf_len = buf_vec[vec_idx].buf_len;
 
-                       /* Prefetch next buffer address. */
-                       if (vec_idx + 1 < nr_vec)
-                               rte_prefetch0((void *)(uintptr_t)
-                                               buf_vec[vec_idx + 1].buf_addr);
                        buf_offset = 0;
                        buf_avail  = buf_len;
                }
@@ -812,8 +807,6 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        break;
                }
 
-               rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
-
                VHOST_LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
                        dev->vid, vq->last_avail_idx,
                        vq->last_avail_idx + num_buffers);
@@ -861,8 +854,6 @@ virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        break;
                }
 
-               rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
-
                VHOST_LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
                        dev->vid, vq->last_avail_idx,
                        vq->last_avail_idx + num_buffers);
@@ -1119,9 +1110,6 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                goto out;
        }
 
-       if (likely(nr_vec > 1))
-               rte_prefetch0((void *)(uintptr_t)buf_vec[1].buf_addr);
-
        if (virtio_net_with_host_offload(dev)) {
                if (unlikely(buf_len < sizeof(struct virtio_net_hdr))) {
                        /*
@@ -1132,7 +1120,6 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        hdr = &tmp_hdr;
                } else {
                        hdr = (struct virtio_net_hdr *)((uintptr_t)buf_addr);
-                       rte_prefetch0(hdr);
                }
        }
 
@@ -1162,9 +1149,6 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                buf_avail = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
        }
 
-       rte_prefetch0((void *)(uintptr_t)
-                       (buf_addr + buf_offset));
-
        PRINT_PACKET(dev,
                        (uintptr_t)(buf_addr + buf_offset),
                        (uint32_t)buf_avail, 0);
@@ -1230,14 +1214,6 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        buf_iova = buf_vec[vec_idx].buf_iova;
                        buf_len = buf_vec[vec_idx].buf_len;
 
-                       /*
-                        * Prefecth desc n + 1 buffer while
-                        * desc n buffer is processed.
-                        */
-                       if (vec_idx + 1 < nr_vec)
-                               rte_prefetch0((void *)(uintptr_t)
-                                               buf_vec[vec_idx + 1].buf_addr);
-
                        buf_offset = 0;
                        buf_avail  = buf_len;
 
@@ -1381,8 +1357,6 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
                if (likely(dev->dequeue_zero_copy == 0))
                        update_shadow_used_ring_split(vq, head_idx, 0);
 
-               rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
-
                pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
                if (unlikely(pkts[i] == NULL)) {
                        RTE_LOG(ERR, VHOST_DATA,
@@ -1492,8 +1466,6 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        update_shadow_used_ring_packed(vq, buf_id, 0,
                                        desc_count);
 
-               rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
-
                pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
                if (unlikely(pkts[i] == NULL)) {
                        RTE_LOG(ERR, VHOST_DATA,