[dpdk-dev] [PATCH v5 09/13] vhost: buffer packed ring dequeue updates

[Marvin Liu]

Buffer used ring updates as many as possible in vhost dequeue function
for coordinating with virtio driver. For supporting buffer, shadow used
ring element should contain descriptor's flags. First shadowed ring
index was recorded for calculating buffered number.

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

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index bf3c30f43..bc4d039df 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -42,6 +42,8 @@
 #define PACKED_DESC_ENQUEUE_USED_FLAG(w)	\
 	((w) ? (VRING_DESC_F_AVAIL | VRING_DESC_F_USED | VRING_DESC_F_WRITE) : \
 		VRING_DESC_F_WRITE)
+#define PACKED_DESC_DEQUEUE_USED_FLAG(w)	\
+	((w) ? (VRING_DESC_F_AVAIL | VRING_DESC_F_USED) : 0x0)
 #define PACKED_DESC_SINGLE_DEQUEUE_FLAG (VRING_DESC_F_NEXT | \
 					 VRING_DESC_F_INDIRECT)
 
@@ -114,6 +116,7 @@ struct log_cache_entry {
 
 struct vring_used_elem_packed {
 	uint16_t id;
+	uint16_t flags;
 	uint32_t len;
 	uint32_t count;
 };
@@ -171,6 +174,8 @@ struct vhost_virtqueue {
 	uint16_t                shadow_used_idx;
 	/* Record packed ring enqueue latest desc cache aligned index */
 	uint16_t		shadow_aligned_idx;
+	/* Record packed ring first dequeue desc index */
+	uint16_t		shadow_last_used_idx;
 	struct vhost_vring_addr ring_addrs;
 
 	struct batch_copy_elem	*batch_copy_elems;
diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index ec17353da..750d16f50 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -154,6 +154,23 @@ vhost_flush_enqueue_shadow_packed(struct virtio_net *dev,
 	vhost_log_cache_sync(dev, vq);
 }
 
+static __rte_always_inline void
+vhost_flush_dequeue_shadow_packed(struct virtio_net *dev,
+				  struct vhost_virtqueue *vq)
+{
+	struct vring_used_elem_packed *used_elem = &vq->shadow_used_packed[0];
+
+	vq->desc_packed[vq->shadow_last_used_idx].id = used_elem->id;
+	rte_smp_wmb();
+	vq->desc_packed[vq->shadow_last_used_idx].flags = used_elem->flags;
+
+	vhost_log_cache_used_vring(dev, vq, vq->shadow_last_used_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
 vhost_flush_enqueue_batch_packed(struct virtio_net *dev,
 				 struct vhost_virtqueue *vq,
@@ -247,6 +264,70 @@ flush_shadow_used_ring_packed(struct virtio_net *dev,
 	vhost_log_cache_sync(dev, vq);
 }
 
+static __rte_always_inline void
+vhost_shadow_dequeue_batch_packed(struct virtio_net *dev,
+				  struct vhost_virtqueue *vq,
+				  uint16_t *ids)
+{
+	uint16_t flags;
+	uint16_t i;
+	uint16_t begin;
+
+	flags = PACKED_DESC_DEQUEUE_USED_FLAG(vq->used_wrap_counter);
+
+	if (!vq->shadow_used_idx) {
+		vq->shadow_last_used_idx = 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].flags = flags;
+		vq->shadow_used_idx++;
+		begin = 1;
+	} else
+		begin = 0;
+
+	for_each_try_unroll(i, begin, PACKED_BATCH_SIZE) {
+		vq->desc_packed[vq->last_used_idx + i].id = ids[i];
+		vq->desc_packed[vq->last_used_idx + i].len = 0;
+	}
+
+	rte_smp_wmb();
+	for_each_try_unroll(i, begin, PACKED_BATCH_SIZE)
+		vq->desc_packed[vq->last_used_idx + i].flags = flags;
+
+	vhost_log_cache_used_vring(dev, vq, vq->last_used_idx *
+				   sizeof(struct vring_packed_desc),
+				   sizeof(struct vring_packed_desc) *
+				   PACKED_BATCH_SIZE);
+	vhost_log_cache_sync(dev, vq);
+
+	vq_inc_last_used_packed(vq, PACKED_BATCH_SIZE);
+}
+
+static __rte_always_inline void
+vhost_shadow_dequeue_single_packed(struct vhost_virtqueue *vq,
+				   uint16_t buf_id,
+				   uint16_t count)
+{
+	if (!vq->shadow_used_idx) {
+		vq->shadow_last_used_idx = vq->last_used_idx;
+
+		vq->shadow_used_packed[0].id  = buf_id;
+		vq->shadow_used_packed[0].len = 0;
+		vq->shadow_used_packed[0].count = count;
+		vq->shadow_used_packed[0].flags =
+			PACKED_DESC_DEQUEUE_USED_FLAG(vq->used_wrap_counter);
+		vq->shadow_used_idx++;
+	} else {
+		vq->desc_packed[vq->last_used_idx].id = buf_id;
+		vq->desc_packed[vq->last_used_idx].len = 0;
+		vq->desc_packed[vq->last_used_idx].flags =
+			PACKED_DESC_DEQUEUE_USED_FLAG(vq->used_wrap_counter);
+	}
+
+	vq_inc_last_used_packed(vq, count);
+}
+
 static __rte_always_inline void
 update_shadow_used_ring_packed(struct vhost_virtqueue *vq,
 			 uint16_t desc_idx, uint32_t len, uint16_t count)
@@ -314,6 +395,26 @@ vhost_shadow_enqueue_single_packed(struct virtio_net *dev,
 	}
 }
 
+static __rte_unused void
+vhost_flush_dequeue_packed(struct virtio_net *dev,
+			   struct vhost_virtqueue *vq)
+{
+	int shadow_count;
+	if (!vq->shadow_used_idx)
+		return;
+
+	shadow_count = vq->last_used_idx - vq->shadow_last_used_idx;
+	if (shadow_count <= 0)
+		shadow_count += vq->size;
+
+	/* buffer used descs as many as possible when doing dequeue */
+	if ((uint32_t)shadow_count >= (vq->size - MAX_PKT_BURST)) {
+		do_data_copy_dequeue(vq);
+		vhost_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))			\
@@ -1788,6 +1889,8 @@ virtio_dev_tx_batch_packed(struct virtio_net *dev,
 			   pkts[i]->pkt_len);
 	}
 
+	vhost_shadow_dequeue_batch_packed(dev, vq, ids);
+
 	vq_inc_last_avail_packed(vq, PACKED_BATCH_SIZE);
 
 	return 0;
@@ -1843,6 +1946,8 @@ virtio_dev_tx_single_packed(struct virtio_net *dev,
 					&desc_count))
 		return -1;
 
+	vhost_shadow_dequeue_single_packed(vq, buf_id, desc_count);
+
 	vq_inc_last_avail_packed(vq, desc_count);
 
 	return 0;
-- 
2.17.1