[RFC v3 3/7] vsock: batch buffers in tx

[Guo Zhi <qtxuning1999@sjtu.edu.cn>]

Vsock uses buffers in order, and for tx driver doesn't have to
know the length of the buffer. So we can do a batch for vsock if
in order negotiated, only write one used ring for a batch of buffers

Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
---
 drivers/vhost/vsock.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 368330417bde..e08fbbb5439e 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -497,7 +497,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
 						 dev);
 	struct virtio_vsock_pkt *pkt;
-	int head, pkts = 0, total_len = 0;
+	int head, pkts = 0, total_len = 0, add = 0;
 	unsigned int out, in;
 	bool added = false;
 
@@ -551,10 +551,18 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 		else
 			virtio_transport_free_pkt(pkt);
 
-		vhost_add_used(vq, head, 0);
+		if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
+			vhost_add_used(vq, head, 0);
+		} else {
+			vq->heads[add].id = head;
+			vq->heads[add++].len = 0;
+		}
 		added = true;
 	} while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
 
+	/* If in order feature negotiaged, we can do a batch to increase performance */
+	if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && added)
+		vhost_add_used_n(vq, vq->heads, add);
 no_more_replies:
 	if (added)
 		vhost_signal(&vsock->dev, vq);
-- 
2.17.1