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

Joe Perches
2013-12-27T17:06:22Z

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)