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

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Date:	Sat, 28 Dec 2013 13:35:35 +0800
From:	Ding Tianhong <dingtianhong@...wei.com>
To:	Joe Perches <joe@...ches.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Julia Lawall <julia.lawall@...6.fr>,
	"David S. Miller" <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 19/20] net: plip: slight optimization of addr
 compare

On 2013/12/28 13:11, Joe Perches wrote:
> On Sat, 2013-12-28 at 13:07 +0800, Ding Tianhong wrote:
>> 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.
> 
> I don't think so.
> 
> I think what you've done so far is fine.
> 
> Any conversions to ether_addr_equal_64bit
> can be done later.
> 

Ok, thanks.

Regards
Ding
> 
> 
> 


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