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

Joe Perches
2013-12-28T05:11:46Z

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.