netdev - Re: [PATCH net-next] vlan: slight optimization for vlan

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Message-Id: <20140304.162436.1110716815887069100.davem@davemloft.net>
Date:	Tue, 04 Mar 2014 16:24:36 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	dingtianhong@...wei.com
Cc:	kaber@...sh.net, joe@...ches.com, julia.lawall@...6.fr,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] vlan: slight optimization for vlan

From: Ding Tianhong <dingtianhong@...wei.com>
Date: Tue, 4 Mar 2014 18:47:30 +0800

> 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.
> 
> 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.:)
> 
> Cc: Joe Perches <joe@...ches.com>
> Cc: Patrick McHardy <kaber@...sh.net>
> Cc: David S. Miller <davem@...emloft.net>
> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>

I agree with Joe that we should only use the optimized routine in
performance critical paths.
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