netdev - Re: [PATCH] - vxlan: gro not effective for intel 82599

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Message-ID: <CALx6S37+es-QD-_41O4cc59_oEX2UeeibZgjd8uOvTcPMHO+nA@mail.gmail.com>
Date:	Fri, 26 Jun 2015 12:59:16 -0700
From:	Tom Herbert <tom@...bertland.com>
To:	Ramu Ramamurthy <sramamur@...ux.vnet.ibm.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Jiri Benc <jbenc@...hat.com>, James Morris <jmorris@...ei.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	pradeeps@...ux.vnet.ibm.com, J Kidambi <jkidambi@...ibm.com>
Subject: Re: [PATCH] - vxlan: gro not effective for intel 82599

On Fri, Jun 26, 2015 at 12:31 PM, Ramu Ramamurthy
<sramamur@...ux.vnet.ibm.com> wrote:
> On 2015-06-26 11:04, Tom Herbert wrote:
>>>
>>> I am testing the simplest configuration which has 1 TCP flow generated by
>>> iperf from
>>> a VM connected to a linux bridge with a vxlan tunnel interface. The 10G
>>> nic
>>> (82599 ES) has
>>> multiple receive queues, but in this simple test, it is likely immaterial
>>> (because, the
>>> tuple on which it hashes would be fixed). The real difference in
>>> performance
>>> appears to
>>> be whether or not vxlan gro is performed by software.
>>>
>>
>> Please do "ethtool -k vxlan0" of whatever interface is for vxlan.
>> Ensure GRO is "on", if not enable it on the interface by "ethtool _k
>> vxlan0 gro on". Run iperf and to tcpdump on the vxlan interface to
>> verify GRO is being done. If we are seeing performance degradation
>> when GRO is being done at tunnel versus device that would be a
>> different problem than no GRO being done at all.
>
>
> Heres more details on the test.
>
> gro is "on" on the device and the tunnel. tcpdump on the vxlan interface
> show un-aggregated packets
>
> [root@...u1 tracing]# tcpdump -i vxlan0
> <snip>
> ptions [nop,nop,TS val 1972850548 ecr 193703], length 1398
> 14:14:38.911955 IP 1.1.1.21.44134 > 1.1.1.11.commplex-link: Flags [.], seq
> 224921449:224922847, ack 1, win 221, options [nop,nop,TS val 1972850548 ecr

Looks like GRO was never implemented for vxlan tunnels. The driver is
simply calling netif_rx instead of using the GRO cells infrastructure.
geneve is doing the same thing. For other tunnels which are used in
foo-over-udp (GRE, IPIP, SIT) ip_tunnel_rcv is called which in turn
calls gro_cells_receive.
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