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Date: Tue, 04 Mar 2014 07:50:05 -0800 From: Joe Perches <joe@...ches.com> To: Ding Tianhong <dingtianhong@...wei.com> Cc: Patrick McHardy <kaber@...sh.net>, "David S. Miller" <davem@...emloft.net>, Julia Lawall <julia.lawall@...6.fr>, Netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net-next] vlan: slight optimization for vlan 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%. > 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. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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