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net: slightly optimize eth_type_trans

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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>
This commit is contained in:
Li RongQing 2018-11-13 09:34:31 +08:00 committed by David S. Miller
parent 982c17b9e3
commit 45cf7959c3
1 changed files with 10 additions and 8 deletions
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18
net/ethernet/eth.c
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@ -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