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

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Message-Id: <20131029.223456.778268322772629087.davem@davemloft.net>
Date:	Tue, 29 Oct 2013 22:34:56 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	hkchu@...gle.com, eric.dumazet@...il.com,
	christoph.paasch@...ouvain.be, netdev@...r.kernel.org,
	mwdalton@...gle.com
Subject: Re: [PATCH v2 net-next] net: introduce gro_frag_list_enable sysctl

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Wed, 30 Oct 2013 10:19:06 +0800

> 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.

Agreed.
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