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

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Message-ID: <1388207506.30298.40.camel@joe-AO722>
Date:	Fri, 27 Dec 2013 21:11:46 -0800
From:	Joe Perches <joe@...ches.com>
To:	Ding Tianhong <dingtianhong@...wei.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 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.


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