[dpdk-dev] [PATCH v2 10/16] vhost: split enqueue and dequeue flush functions

[Marvin Liu]

Vhost enqueue descriptors are updated by burst number, while vhost
dequeue descriptors are buffered. Meanwhile in dequeue function only
first descriptor is buffered. Due to these differences, split vhost
enqueue and dequeue flush functions.

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

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 94c1b8dc7..c5c86c219 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -92,8 +92,7 @@ update_shadow_split(struct vhost_virtqueue *vq,
 }
 
 static __rte_always_inline void
-flush_shadow_packed(struct virtio_net *dev,
-			struct vhost_virtqueue *vq)
+flush_enqueue_shadow_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
 {
 	int i;
 	uint16_t used_idx = vq->last_used_idx;
@@ -158,6 +157,31 @@ flush_shadow_packed(struct virtio_net *dev,
 	vhost_log_cache_sync(dev, vq);
 }
 
+static __rte_always_inline void
+flush_dequeue_shadow_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
+{
+	uint16_t head_idx = vq->dequeue_shadow_head;
+	uint16_t head_flags;
+	struct vring_used_elem_packed *used_elem = &vq->shadow_used_packed[0];
+
+	if (used_elem->used_wrap_counter)
+		head_flags = VIRTIO_TX_USED_FLAG;
+	else
+		head_flags = VIRTIO_TX_USED_WRAP_FLAG;
+
+	vq->desc_packed[head_idx].id = used_elem->id;
+
+	rte_smp_wmb();
+	vq->desc_packed[head_idx].flags = head_flags;
+
+	vhost_log_cache_used_vring(dev, vq, head_idx *
+				   sizeof(struct vring_packed_desc),
+				   sizeof(struct vring_packed_desc));
+
+	vq->shadow_used_idx = 0;
+	vhost_log_cache_sync(dev, vq);
+}
+
 static __rte_always_inline void
 update_shadow_packed(struct vhost_virtqueue *vq,
 			 uint16_t desc_idx, uint32_t len, uint16_t count)
@@ -200,6 +224,51 @@ flush_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	}
 }
 
+static __rte_always_inline void
+update_dequeue_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
+	uint16_t *ids)
+{
+	uint16_t flags = 0;
+	uint16_t i;
+
+	if (vq->used_wrap_counter)
+		flags = VIRTIO_TX_USED_FLAG;
+	else
+		flags = VIRTIO_TX_USED_WRAP_FLAG;
+
+	if (!vq->shadow_used_idx) {
+		vq->dequeue_shadow_head = vq->last_used_idx;
+
+		vq->shadow_used_packed[0].id  = ids[0];
+		vq->shadow_used_packed[0].len = 0;
+		vq->shadow_used_packed[0].count = 1;
+		vq->shadow_used_packed[0].used_idx = vq->last_used_idx;
+		vq->shadow_used_packed[0].used_wrap_counter =
+			vq->used_wrap_counter;
+
+		UNROLL_PRAGMA(PRAGMA_PARAM)
+		for (i = 1; i < PACKED_DESCS_BURST; i++)
+			vq->desc_packed[vq->last_used_idx + i].id = ids[i];
+
+		UNROLL_PRAGMA(PRAGMA_PARAM)
+		for (i = 1; i < PACKED_DESCS_BURST; i++) {
+			rte_smp_wmb();
+			vq->desc_packed[vq->last_used_idx + i].flags = flags;
+		}
+
+		vq->shadow_used_idx = 1;
+
+		vq->last_used_idx += PACKED_DESCS_BURST;
+		if (vq->last_used_idx >= vq->size) {
+			vq->used_wrap_counter ^= 1;
+			vq->last_used_idx -= vq->size;
+		}
+	} else {
+		uint64_t lens[PACKED_DESCS_BURST] = {0};
+		flush_burst_packed(dev, vq, lens, ids, flags);
+	}
+}
+
 static __rte_always_inline void
 flush_enqueue_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint64_t *lens, uint16_t *ids)
@@ -309,10 +378,29 @@ flush_enqueue_packed(struct virtio_net *dev,
 
 		if (vq->enqueue_shadow_count >= PACKED_DESCS_BURST) {
 			do_data_copy_enqueue(dev, vq);
-			flush_shadow_packed(dev, vq);
+			flush_enqueue_shadow_packed(dev, vq);
 		}
 	}
 }
+
+static __rte_unused __rte_always_inline void
+flush_dequeue_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
+{
+	if (!vq->shadow_used_idx)
+		return;
+
+	int16_t shadow_count = vq->last_used_idx - vq->dequeue_shadow_head;
+	if (shadow_count <= 0)
+		shadow_count += vq->size;
+
+	/* buffer used descs as many as possible when doing dequeue */
+	if ((uint16_t)shadow_count >= (vq->size - MAX_PKT_BURST)) {
+		do_data_copy_dequeue(vq);
+		flush_dequeue_shadow_packed(dev, vq);
+		vhost_vring_call_packed(dev, vq);
+	}
+}
+
 /* avoid write operation when necessary, to lessen cache issues */
 #define ASSIGN_UNLESS_EQUAL(var, val) do {	\
 	if ((var) != (val))			\
@@ -1178,7 +1266,7 @@ virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	do_data_copy_enqueue(dev, vq);
 
 	if (likely(vq->shadow_used_idx)) {
-		flush_shadow_packed(dev, vq);
+		flush_enqueue_shadow_packed(dev, vq);
 		vhost_vring_call_packed(dev, vq);
 	}
 
@@ -1810,6 +1898,7 @@ virtio_dev_tx_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			   pkts[i]->pkt_len);
 	}
 
+	update_dequeue_burst_packed(dev, vq, ids);
 	if (virtio_net_with_host_offload(dev)) {
 		UNROLL_PRAGMA(PRAGMA_PARAM)
 		for (i = 0; i < PACKED_DESCS_BURST; i++) {
@@ -1911,7 +2000,7 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		}
 
 		if (likely(vq->shadow_used_idx)) {
-			flush_shadow_packed(dev, vq);
+			flush_dequeue_shadow_packed(dev, vq);
 			vhost_vring_call_packed(dev, vq);
 		}
 	}
@@ -1990,7 +2079,7 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		if (unlikely(i < count))
 			vq->shadow_used_idx = i;
 		if (likely(vq->shadow_used_idx)) {
-			flush_shadow_packed(dev, vq);
+			flush_dequeue_shadow_packed(dev, vq);
 			vhost_vring_call_packed(dev, vq);
 		}
 	}
-- 
2.17.1