net: slightly optimize eth_type_trans

netperf udp stream shows that eth_type_trans takes certain cpu, so adjust the mac address check order, and firstly check if it is device address, and only check if it is multicast address only if not the device address. After this change: To unicast, and skb dst mac is device mac, this is most of time reduce a comparision To unicast, and skb dst mac is not device mac, nothing change To multicast, increase a comparision Before: 1.03% [kernel] [k] eth_type_trans After: 0.78% [kernel] [k] eth_type_trans Signed-off-by: Zhang Yu <[email protected]> Signed-off-by: Li RongQing <[email protected]> Signed-off-by: David S. Miller <[email protected]>
ambv · Nov 15, 2018 · 45cf795 · 45cf795
1 parent 982c17b
commit 45cf795
Showing 1 changed file with 10 additions and 8 deletions.
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
@@ -165,15 +165,17 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
 	eth = (struct ethhdr *)skb->data;
 	skb_pull_inline(skb, ETH_HLEN);
 
-	if (unlikely(is_multicast_ether_addr_64bits(eth->h_dest))) {
-		if (ether_addr_equal_64bits(eth->h_dest, dev->broadcast))
-			skb->pkt_type = PACKET_BROADCAST;
-		else
-			skb->pkt_type = PACKET_MULTICAST;
+	if (unlikely(!ether_addr_equal_64bits(eth->h_dest,
+					      dev->dev_addr))) {
+		if (unlikely(is_multicast_ether_addr_64bits(eth->h_dest))) {
+			if (ether_addr_equal_64bits(eth->h_dest, dev->broadcast))
+				skb->pkt_type = PACKET_BROADCAST;
+			else
+				skb->pkt_type = PACKET_MULTICAST;
+		} else {
+			skb->pkt_type = PACKET_OTHERHOST;
+		}
 	}
-	else if (unlikely(!ether_addr_equal_64bits(eth->h_dest,
-						   dev->dev_addr)))
-		skb->pkt_type = PACKET_OTHERHOST;
 
 	/*
 	 * Some variants of DSA tagging don't have an ethertype field