netdev - Re: [0/14] GRO: Lots of microoptimisations

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Message-ID: <20090612160926.GA4290@neterion.com>
Date:	Fri, 12 Jun 2009 12:09:26 -0400
From:	Benjamin LaHaise <ben.lahaise@...erion.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	netdev@...r.kernel.org
Subject: Re: [0/14] GRO: Lots of microoptimisations

On Wed, Jun 10, 2009 at 03:44:49PM +1000, Herbert Xu wrote:
> On Fri, May 29, 2009 at 12:23:13PM -0400, Benjamin LaHaise wrote:
> >
> > It's just being turned off by setting a loadable module option.
> 
> Let me see if I can get my hands on a machine with your NIC.

I found at least one reason why: the first skb_shinfo()->frag_list touch 
in dev_gro_receive() was causing a cache miss.  Adding a prefetch in the 
driver helps that a little bit, but there's still > 500Mbps difference.  
I'd like to retest on a system with newer CPUs, but it will probably be a 
few weeks until all the hardware is in the same place.

		-ben
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