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 >> >> >> > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html