From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH net-next 19/20] net: plip: slight optimization of addr compare Date: Fri, 27 Dec 2013 09:06:22 -0800 Message-ID: <1388163982.30298.12.camel@joe-AO722> References: <52BD22ED.4030302@huawei.com> <1388159283.12212.80.camel@edumazet-glaptop2.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Ding Tianhong , "David S. Miller" , Netdev , "linux-kernel@vger.kernel.org" To: Eric Dumazet , Julia Lawall Return-path: In-Reply-To: <1388159283.12212.80.camel@edumazet-glaptop2.roam.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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)