netdev - Re: vxlan/veth performance issues on net.git + latest kernels

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Date:	Wed, 4 Dec 2013 17:20:03 +0200
From:	Or Gerlitz <or.gerlitz@...il.com>
To:	Joseph Gasparakis <joseph.gasparakis@...el.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Jerry Chu <hkchu@...gle.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Pravin B Shelar <pshelar@...ira.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: vxlan/veth performance issues on net.git + latest kernels

On Wed, Dec 4, 2013 at 11:41 AM, Or Gerlitz <or.gerlitz@...il.com> wrote:
> On Wed, Dec 4, 2013 at 11:24 AM, Joseph Gasparakis
> <joseph.gasparakis@...el.com> wrote:
>> On Wed, 4 Dec 2013, Or Gerlitz wrote:
>
>>> nope! with the latest net tree, after handle_offloads is called in
>>> vxlan_xmit_skb and before iptunnel_xmit is invoked,
>>> skb_shinfo(skb)->gso_type is either 0 or 0x201 which is
>>> (SKB_GSO_UDP_TUNNEL | SKB_GSO_TCPV4) and its the same value whether
>>> the session runs over veth device or directly over the bridge, where
>>> over veth and > 1 stream we see drops, bad perf, etc.
>>> I am very interested in the VM case too, so will check it out and let you know.
>
>> Ok, I was really hoping that would be the same...
>
> So when running traffic from VM I do see SKB_GSO_DODGY bit being set!
> my environment for running VMs with sane peformance was screwed  a bit, I will bring it
> up later today and see if unsetting the bit helps.

so if the DODGY bit is left set, it simply doesn't work! it seems that
guest GSO packets are just dropped

As for the performance when the bit is unset in the vxlan driver as
you suggested, I need to tune the VMs a bit more, later or tomorrow
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