netdev - Re: [PATCH v2 net-next] net: introduce gro_frag_list

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Message-ID: <20131030021905.GA2089@gondor.apana.org.au>
Date:	Wed, 30 Oct 2013 10:19:06 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Jerry Chu <hkchu@...gle.com>
Cc:	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Christoph Paasch <christoph.paasch@...ouvain.be>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Michael Dalton <mwdalton@...gle.com>
Subject: Re: [PATCH v2 net-next] net: introduce gro_frag_list_enable sysctl

On Tue, Oct 29, 2013 at 07:13:50PM -0700, Jerry Chu wrote:
> On Tue, Oct 29, 2013 at 7:05 PM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> > If we are indeed able to do that, I doubt we would even need
> > the sysctl patch since the GRO performance should be vastly
> > superior to the non-GRO case, even for a router/bridge.
> 
> Probably not the case for the simple forwarding case. See my
> test result of some small (5-8%) CPU+throughput penalty from
> GRO (over GRE tunnel) posted previously. But I can believe
> the number may be very different if the forwarding path involves
> more work (NAT, iptables filtering,...,etc) resulting in a higher per
> pkt cost.

Your numbers are with Eric's current patch that just linearises
the packet, what I'm saying is that you don't need to linearise
these packets since the packet boundaries are still there, just
hidden inside each frag_list.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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