diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 2af89b6..cd547d0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -470,6 +470,10 @@
  */
 	spinlock_t		_xmit_lock ____cacheline_aligned_in_smp;
 	int			xmit_lock_owner;
+	/*
+	 * please use this field instead of dev->trans_start
+	 */
+	unsigned long		trans_start;
 } ____cacheline_aligned_in_smp;
 
 
@@ -819,6 +823,11 @@
  * One part is mostly used on xmit path (device)
  */
 	/* These may be needed for future network-power-down code. */
+
+	/*
+	 * trans_start here is expensive for high speed devices on SMP,
+	 * please use netdev_queue->trans_start instead.
+	 */
 	unsigned long		trans_start;	/* Time (in jiffies) of last Tx	*/
 
 	int			watchdog_timeo; /* used by dev_watchdog() */
@@ -1541,6 +1550,8 @@
 	return !test_bit(__LINK_STATE_NOCARRIER, &dev->state);
 }
 
+extern unsigned long dev_trans_start(struct net_device *dev);
+
 extern void __netdev_watchdog_up(struct net_device *dev);
 
 extern void netif_carrier_on(struct net_device *dev);