Re: [PATCH net-next 19/20] net: plip: slight optimization of addr compare

Ding Tianhong
2013-12-28T05:08:13Z

On 2013/12/28 1:06, Joe Perches wrote:
> On Fri, 2013-12-27 at 07:48 -0800, Eric Dumazet wrote:
>> On Fri, 2013-12-27 at 14:49 +0800, Ding Tianhong wrote:
>>> Use possibly more efficient ether_addr_equal
>>> to instead of memcmp.
> []
>>> diff --git a/drivers/net/plip/plip.c b/drivers/net/plip/plip.c
> []
>>> @@ -549,7 +549,7 @@ static __be16 plip_type_trans(struct sk_buff *skb, struct net_device *dev)
>>>
>>> if(*eth->h_dest&1)
>>> {
>>> - if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
>>> + if(ether_addr_equal(eth->h_dest, dev->broadcast))
>>> skb->pkt_type=PACKET_BROADCAST;
>>> else
>>> skb->pkt_type=PACKET_MULTICAST;
>>
>> What about :
>>
>> if (is_multicast_ether_addr(eth->h_dest)) {
>> if (ether_addr_equal_64bits(eth->h_dest, dev->broadcast))
>> skb->pkt_type = PACKET_BROADCAST;
>> else
>> skb->pkt_type = PACKET_MULTICAST;
>> }
>
> That is better though I wonder how many systems are
> still using laplink via parallel null-printer cables.
>
> No matter, better is better.
>
> The same optimization using ether_addr_equal_64bits
> may be possible to do in other places given other
> structs too.
>
> Perhaps it's a possible spatch/coccinelle conversion,
>
> I don't know spatch well enough to know if a
> mechanism to check if structure members have other
> fields that follow them in the structure or if the
> structure member is an array of a minimum size.
>
> Maybe Julia does. (cc'd)
>
>
As the below patch said, that a lot of ether_addr_equal
could be instead of ether_addr_equal_64bits, and I need to
review them and resend.

Regards
Ding

>