netdev - Re: [PATCH net-next 0/4] net: cleanup for UDP tunnel's GRO

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Date:	Fri, 8 Jul 2016 16:57:10 -0400
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Shmulik Ladkani <shmulik.ladkani@...il.com>,
	Alexander Duyck <alexander.duyck@...il.com>,
	Paolo Abeni <pabeni@...hat.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jesse Gross <jesse@...nel.org>,
	Tom Herbert <tom@...bertland.com>, Jiri Benc <jbenc@...hat.com>
Subject: Re: [PATCH net-next 0/4] net: cleanup for UDP tunnel's GRO

On 08.07.2016 16:17, Shmulik Ladkani wrote:
> On Fri, 8 Jul 2016 09:21:40 -0700 Alexander Duyck <alexander.duyck@...il.com> wrote:
>> On Thu, Jul 7, 2016 at 8:58 AM, Paolo Abeni <pabeni@...hat.com> wrote:
>>> With udp tunnel offload in place, the kernel can do GRO for some udp tunnels
>>> at the ingress device level. Currently both the geneve and the vxlan drivers
>>> implement an additional GRO aggregation point via gro_cells.
>>> The latter takes effect for tunnels using zero checksum udp packets, which are
>>> currently explicitly not aggregated by the udp offload layer.
>>>
>>> This patch series adapts the udp tunnel offload to process also zero checksum
>>> udp packets, if the tunnel's socket allow it. Aggregation, if possible is always
>>> performed at the ingress device level.
>>>
>>> Then the gro_cells hooks, in both vxlan and geneve driver are removed.  
>>
>> I think removing the gro_cells hooks may be taking things one step too far.
> 
> +1
> 
>> I get that there is an impression that it is redundant but there are a
>> number of paths that could lead to VXLAN or GENEVE frames being
>> received that are not aggregated via GRO.
> 
> There's the case where the vxlan/geneve datagrams get IP fragmented, and
> IP frags are not GROed.
> GRO aggregation at the vxlan/geneve level is beneficial for this case.

Isn't this a misconfiguration? TCP should not fragment at all, not even
in vxlan/geneve if one cares about performance? And UDP is not GRO'ed
anyway.

Bye,
Hannes