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 14:11:07 +0800 Message-ID: <5316BFFB.9090502@huawei.com> References: <5315AF42.8030905@huawei.com> <1393948205.20435.28.camel@joe-AO722> <53167A3A.1050407@huawei.com> 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 szxga03-in.huawei.com ([119.145.14.66]:25335 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719AbaCEGMS (ORCPT ); Wed, 5 Mar 2014 01:12:18 -0500 In-Reply-To: <53167A3A.1050407@huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2014/3/5 9:13, Ding Tianhong wrote: > 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. >> Hi Joe: My test case is very simple, use iperf to test the vlan dev, and compare the %system time that add unlikely or not, do you have any suggestion for that, or gave me some advise, thanks a lot. Regards Ding >> I presume a single stream of identical vlan PACKET_OTHERHOST >> packets is atypical. >> > > OK > > Regards > Ding >> >> >> >