From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong Subject: Re: [PATCH net-next] vlan: slight optimization for vlan Date: Wed, 5 Mar 2014 09:13:30 +0800 Message-ID: <53167A3A.1050407@huawei.com> References: <5315AF42.8030905@huawei.com> <1393948205.20435.28.camel@joe-AO722> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Patrick McHardy , "David S. Miller" , Julia Lawall , Netdev To: Joe Perches Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:56871 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755209AbaCEBOI (ORCPT ); Tue, 4 Mar 2014 20:14:08 -0500 In-Reply-To: <1393948205.20435.28.camel@joe-AO722> Sender: netdev-owner@vger.kernel.org List-ID: On 2014/3/4 23:50, Joe Perches wrote: > On Tue, 2014-03-04 at 18:47 +0800, Ding Tianhong wrote: >> Ether_addr_equal_64bits is more efficient than ether_addr_equal, and >> can be used when each argument is an array within a structure that >> contains at least two bytes of data beyond the array, so it is safe >> to use it for vlan. > > Perhaps I wasn't clear or perhaps you simply disagree, > (which is certainly your right), but I think that > ether_addr_equal_64bits should _only_ be used in > performance sensitive paths because using it requires > a person/script to analyze surrounding structures to > ensure 2 bytes exist after the address. > > I don't think that vlan_dev_(open|stop|set_mac_address) > are performance sensitive paths. > > vlan_do_receive, absolutely yes. > > Is the vlan_device_event:NETDEV_CHANGEADDR:vlan_sync_address > path that frequent? Maybe. > >> On a simple test by iperf, it reduces the CPU %system time from 14% to 12%. > Totally agree with you, use the XXX_64bits in slow path make no sense, thanks a lot. >> According Joe's suggestion, maybe it'd be faster to add an unlikely to >> the test for PCKET_OTHERHOST, so I add it and see whether the performance >> could be better, but the differences is so small and negligible, maybe my >> test case is not effective enough, but I still add the unlikely and wait to >> hear more opinions.:) > > A separate patch for the unlikely would likely be better, > but I wonder what your test case is. > > I presume a single stream of identical vlan PACKET_OTHERHOST > packets is atypical. > OK Regards Ding > > >