[dpdk-dev] [PATCH v1 10/14] vhost: optimize Rx function of packed ring

[Marvin Liu <yong.liu@intel.com>]

Optimize vhost device rx function by separate descriptors, no-chained
and direct descriptors will be handled by burst and other will be
handled one by one as before. Pre-fetch descriptors in next two cache
lines as hardware will load two cache line data automatically.

Signed-off-by: Marvin Liu <yong.liu@intel.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 8d09e1611..269ec8a43 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -769,64 +769,6 @@ fill_vec_buf_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	return 0;
 }
 
-/*
- * Returns -1 on fail, 0 on success
- */
-static inline int
-reserve_avail_buf_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
-				uint32_t size, struct buf_vector *buf_vec,
-				uint16_t *nr_vec, uint16_t *num_buffers,
-				uint16_t *nr_descs)
-{
-	uint16_t avail_idx;
-	uint16_t vec_idx = 0;
-	uint16_t max_tries, tries = 0;
-
-	uint16_t buf_id = 0;
-	uint32_t len = 0;
-	uint16_t desc_count;
-
-	*num_buffers = 0;
-	avail_idx = vq->last_avail_idx;
-
-	if (rxvq_is_mergeable(dev))
-		max_tries = vq->size - 1;
-	else
-		max_tries = 1;
-
-	while (size > 0) {
-		/*
-		 * if we tried all available ring items, and still
-		 * can't get enough buf, it means something abnormal
-		 * happened.
-		 */
-		if (unlikely(++tries > max_tries))
-			return -1;
-
-		if (unlikely(fill_vec_buf_packed(dev, vq,
-						avail_idx, &desc_count,
-						buf_vec, &vec_idx,
-						&buf_id, &len,
-						VHOST_ACCESS_RW) < 0))
-			return -1;
-
-		len = RTE_MIN(len, size);
-		update_shadow_packed(vq, buf_id, len, desc_count);
-		size -= len;
-
-		avail_idx += desc_count;
-		if (avail_idx >= vq->size)
-			avail_idx -= vq->size;
-
-		*nr_descs += desc_count;
-		*num_buffers += 1;
-	}
-
-	*nr_vec = vec_idx;
-
-	return 0;
-}
-
 static __rte_noinline void
 copy_vnet_hdr_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		struct buf_vector *buf_vec,
@@ -1120,7 +1062,7 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	return pkt_idx;
 }
 
-static __rte_unused uint16_t
+static __rte_always_inline uint16_t
 virtio_dev_rx_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	 struct rte_mbuf **pkts)
 {
@@ -1229,7 +1171,7 @@ virtio_dev_rx_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	return 0;
 }
 
-static __rte_unused int16_t
+static __rte_always_inline int16_t
 virtio_dev_rx_single_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	struct rte_mbuf *pkt)
 {
@@ -1263,46 +1205,45 @@ virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	struct rte_mbuf **pkts, uint32_t count)
 {
 	uint32_t pkt_idx = 0;
-	uint16_t num_buffers;
-	struct buf_vector buf_vec[BUF_VECTOR_MAX];
+	uint32_t pkt_num;
+	uint32_t remained = count;
+	uint16_t fetch_idx;
+	int ret;
+	struct vring_packed_desc *descs = vq->desc_packed;
 
-	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
-		uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
-		uint16_t nr_vec = 0;
-		uint16_t nr_descs = 0;
+	do {
+		if ((vq->last_avail_idx & 0x7) == 0) {
+			fetch_idx = vq->last_avail_idx + 8;
+			rte_prefetch0((void *)(uintptr_t)&descs[fetch_idx]);
+		}
 
-		if (unlikely(reserve_avail_buf_packed(dev, vq,
-						pkt_len, buf_vec, &nr_vec,
-						&num_buffers, &nr_descs) < 0)) {
-			VHOST_LOG_DEBUG(VHOST_DATA,
-				"(%d) failed to get enough desc from vring\n",
-				dev->vid);
-			vq->shadow_used_idx -= num_buffers;
-			break;
+		if (remained >= PACKED_DESCS_BURST) {
+			ret = virtio_dev_rx_burst_packed(dev, vq, pkts);
+
+			if (!ret) {
+				pkt_num = PACKED_DESCS_BURST;
+				pkt_idx += pkt_num;
+				remained -= pkt_num;
+				continue;
+			}
 		}
 
-		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);
+		pkt_num = virtio_dev_rx_single_packed(dev, vq, pkts[pkt_idx]);
 
-		if (copy_mbuf_to_desc(dev, vq, pkts[pkt_idx],
-						buf_vec, nr_vec,
-						num_buffers) < 0) {
-			vq->shadow_used_idx -= num_buffers;
+		if (pkt_num == 0)
 			break;
-		}
 
-		vq->last_avail_idx += nr_descs;
-		if (vq->last_avail_idx >= vq->size) {
-			vq->last_avail_idx -= vq->size;
-			vq->avail_wrap_counter ^= 1;
-		}
-	}
+		pkt_idx += pkt_num;
+		remained -= pkt_num;
 
-	do_data_copy_enqueue(dev, vq);
+	} while (pkt_idx < count);
+
+	if (pkt_idx) {
+		if (vq->shadow_used_idx) {
+			do_data_copy_enqueue(dev, vq);
+			flush_enqueue_shadow_packed(dev, vq);
+		}
 
-	if (likely(vq->shadow_used_idx)) {
-		flush_enqueue_shadow_packed(dev, vq);
 		vhost_vring_call_packed(dev, vq);
 	}
 
-- 
2.17.1