ethernet: use likely() for common Ethernet encap

Mark code path's likely/unlikely based on most common usage.
  * Very few devices use dsa tags.
  * Most traffic is Ethernet (not 802.2)
  * No sane person uses trailer type or Novell encapsulation

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index f777e17d28c8..8f032bae60ad 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -179,12 +179,13 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
          * variants has been configured on the receiving interface,
          * and if so, set skb->protocol without looking at the packet.
          */
-        if (netdev_uses_dsa_tags(dev))
+        if (unlikely(netdev_uses_dsa_tags(dev)))
                 return htons(ETH_P_DSA);
-        if (netdev_uses_trailer_tags(dev))
+
+        if (unlikely(netdev_uses_trailer_tags(dev)))
                 return htons(ETH_P_TRAILER);
 
-        if (ntohs(eth->h_proto) >= ETH_P_802_3_MIN)
+        if (likely(ntohs(eth->h_proto) >= ETH_P_802_3_MIN))
                 return eth->h_proto;
 
         /*
@@ -193,7 +194,7 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
          *      layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
          *      won't work for fault tolerant netware but does for the rest.
          */
-        if (skb->len >= 2 && *(unsigned short *)(skb->data) == 0xFFFF)
+        if (unlikely(skb->len >= 2 && *(unsigned short *)(skb->data) == 0xFFFF))
                 return htons(ETH_P_802_3);
 
         /*