Index: if_vtnet.c
===================================================================
--- if_vtnet.c	(revision 248477)
+++ if_vtnet.c	(working copy)
@@ -167,6 +167,7 @@
 static int	vtnet_enable_tx_intr(struct vtnet_softc *);
 static void	vtnet_disable_rx_intr(struct vtnet_softc *);
 static void	vtnet_disable_tx_intr(struct vtnet_softc *);
+static int	vtnet_tx_blocked(struct vtnet_softc *);
 
 /* Tunables. */
 static int vtnet_csum_disable = 0;
@@ -584,6 +585,25 @@
 }
 
 static int
+vtnet_tx_blocked(struct vtnet_softc *sc)
+{
+	struct ifnet *ifp;
+
+	VTNET_LOCK_ASSERT(sc);
+
+	ifp = sc->vtnet_ifp;
+
+	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
+	    (sc->vtnet_flags & VTNET_FLAG_LINK) == 0)
+		return (0);
+
+	if ((ifp->if_drv_flags & IFF_DRV_OACTIVE) != 0)
+		return (1);
+
+	return (0);
+}
+
+static int
 vtnet_config_change(device_t dev)
 {
 	struct vtnet_softc *sc;
@@ -791,13 +811,20 @@
 static void
 vtnet_config_change_task(void *arg, int pending)
 {
+	int txblocked;
 	struct vtnet_softc *sc;
 
 	sc = arg;
 
 	VTNET_LOCK(sc);
 	vtnet_update_link_status(sc);
+	txblocked = vtnet_tx_blocked(sc);
 	VTNET_UNLOCK(sc);
+
+#ifdef VTNET_TX_INTR_MODERATION
+	if (txblocked)
+		taskqueue_enqueue_fast(sc->vtnet_tq, &sc->vtnet_tx_intr_task);
+#endif
 }
 
 static int
@@ -1999,13 +2026,20 @@
 static void
 vtnet_start(struct ifnet *ifp)
 {
+	int txblocked;
 	struct vtnet_softc *sc;
 
 	sc = ifp->if_softc;
 
 	VTNET_LOCK(sc);
 	vtnet_start_locked(ifp);
+	txblocked = vtnet_tx_blocked(sc);
 	VTNET_UNLOCK(sc);
+
+#ifdef VTNET_TX_INTR_MODERATION
+	if (txblocked)
+		taskqueue_enqueue_fast(sc->vtnet_tq, &sc->vtnet_tx_intr_task);
+#endif
 }
 
 static void
@@ -2732,10 +2766,11 @@
 {
 
 #ifdef VTNET_TX_INTR_MODERATION
-	return (0);
-#else
+	if (!vtnet_tx_blocked(sc) ||
+	    (sc->vtnet_features & VIRTIO_F_NOTIFY_ON_EMPTY) != 0)
+		return (0);
+#endif
 	return (virtqueue_enable_intr(sc->vtnet_tx_vq));
-#endif
 }
 
 static void