Subject: Re: [PATCH net-next] vlan: use ether_addr_equal_64bits to instead of ether_addr_equal

From: Ding Tianhong <[email-masked]>
Date: Mon, 3 Mar 2014 10:49:36 +0800

On 2014/3/3 9:49, Joe Perches wrote:
> On Mon, 2014-03-03 at 09:14 +0800, Ding Tianhong wrote:
>> Ether_addr_equal_64bits is more efficient than ether_addr_equal, and
>> can be used when each argument is an array within a structure that
>> contains at least two bytes of data beyond the array, so it is safe
>> to use it for vlan.
> []
>> diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
> []
>> @@ -26,7 +26,7 @@ bool vlan_do_receive(struct sk_buff **skbp)
>>  		/* Our lower layer thinks this is not local, let's make sure.
>>  		 * This allows the VLAN to have a different MAC than the
>>  		 * underlying device, and still route correctly. */
>> -		if (ether_addr_equal(eth_hdr(skb)->h_dest, vlan_dev->dev_addr))
>> +		if (ether_addr_equal_64bits(eth_hdr(skb)->h_dest, vlan_dev->dev_addr))
>>  			skb->pkt_type = PACKET_HOST;
>>  	}
> 
> Hi again Ding
> 
> If you do have performance numbers:
> 
> The lines above this ether_addr_equal_64 are:
> 
> 	if (skb->pkt_type == PACKET_OTHERHOST) {
> 		/* Our lower layer thinks this is not local, let's make sure.
> 		 * This allows the VLAN to have a different MAC than the
> 		 * underlying device, and still route correctly. */
> 		if (ether_addr_equal(eth_hdr(skb)->h_dest, vlan_dev->dev_addr))
> 			skb->pkt_type = PACKET_HOST;
> 	}
> 
> Maybe it'd be faster overall to add an unlikely
> to the == test
> 
> 	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
> 
> 
> 

Sorry, I can't understand it clearly, do you mean that if the skb deliver to the vlan dev,
it is impossible that the pkt_type is PACKET_OTHERHOST at most time?

Regards
Ding