Re: [PATCH net-next 11/11] vhost_net: batch submitting XDP buffers to underlayer sockets

On Fri, Sep 07, 2018 at 03:41:52PM +0800, Jason Wang wrote:

quoted

quoted

@@ -556,10 +667,14 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
  	size_t len, total_len = 0;
  	int err;
  	int sent_pkts = 0;
+	bool bulking = (sock->sk->sk_sndbuf == INT_MAX);

What does bulking mean?

The name is misleading, it means whether we can do batching. For simplicity,
I disable batching is sndbuf is not INT_MAX.

But what does batching have to do with sndbuf?

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  	for (;;) {
  		bool busyloop_intr = false;
+		if (nvq->done_idx == VHOST_NET_BATCH)
+			vhost_tx_batch(net, nvq, sock, &msg);
+
  		head = get_tx_bufs(net, nvq, &msg, &out, &in, &len,
  				   &busyloop_intr);
  		/* On error, stop handling until the next kick. */

@@ -577,14 +692,34 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
  			break;
  		}
-		vq->heads[nvq->done_idx].id = cpu_to_vhost32(vq, head);
-		vq->heads[nvq->done_idx].len = 0;
-
  		total_len += len;
-		if (tx_can_batch(vq, total_len))
-			msg.msg_flags |= MSG_MORE;
-		else
-			msg.msg_flags &= ~MSG_MORE;
+
+		/* For simplicity, TX batching is only enabled if
+		 * sndbuf is unlimited.

What if sndbuf changes while this processing is going on?

We will get the correct sndbuf in the next run of handle_tx(). I think this
is safe.

If it's safe why bother with special-casing INT_MAX?

-- 
MST