Commit 45cf7959 authored Nov 13, 2018 by Li RongQing Committed by David S. Miller Nov 15, 2018

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 <zhangyu31@baidu.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 982c17b9

net/ethernet/eth.c

+10 −8

Original line number	Diff line number	Diff line
		@@ -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(!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 if (unlikely(!ether_addr_equal_64bits(eth->h_dest,
		dev->dev_addr)))
		} else {
		skb->pkt_type = PACKET_OTHERHOST;
		}
		}

		/*
		* Some variants of DSA tagging don't have an ethertype field

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