Re: [Xen-users] Xen/OVS - VLAN offloading

[Eugene Istomin <e.istomin@xxxxxxx>]

Ian,

in my testbed untagged by OVS have ~2 times more bandwith than untagged by VM.

All interfaces have MTU=9000


1)untagged by VM interface (in OVS like "trunks: [1002]")

#atop from VM
NET | transport    | tcpi   22733 | tcpo   80191 | udpi       0 | udpo       4 |
NET | eth0    ---- | pcki   22736 | pcko   80243 | si   12 Mbps | so 5777 Mbps |
NET | vlan100 ---- | pcki   22738 | pcko   80245 | si 9495 Kbps | so 5775 Mbps |

#atop from Dom0
CPU | sys      57% | irq      39%   
cpu | sys      58% | irq      41%  
..
NET | vif1.0  ---- |  pcki  227727 | pcko  797502  | si   10 Mbps |  so 5743 
Mbps 
NET | vif2.0  ---- |  pcki  797748 | pcko  227717  | si 5736 Mbps |  so   12 
Mbps 



2) untagged by OVS interface (in OVS like "tag: 1002")
#atop from VM  - untagged by OVS interface
NET | transport    | tcpi    8495 | tcpo  163131 | udpi       0 | udpo       0
NET | eth1    ---- | pcki    8495 | pcko   24718 | si 4485 Kbps | so   11 Gbps

#atop from Dom0
CPU | sys      96% | irq       4%  
cpu | sys      96% | irq       4% 
..
NET | vif1.1  ---- |  pcki   75974 | pcko  247608  | si 3160 Kbps |  so   11 
Gbps
NET | vif2.1  ---- |  pcki  247616 | pcko   75971  | si   11 Gbps |  so 4011 
Kbps 


As you can see second variant have full netback sys load in DOM0. Second have 
high number 
of irq and high numbers of pcki/pcko.
Is this behavior correct?
-- 
Best regards,
Eugene Istomin



On Friday, May 31, 2013 08:41:29 AM Ian Campbell wrote:
> On Fri, 2013-05-31 at 06:53 +0300, Eugene Istomin wrote:
> > As i see, VLAN offloading is partially implemented in OVS and didn't
> > implemented in Xen means VLAN tagged traffic inside VM will make
> > additional latency.
> 
> I'm not sure what you mean here, but it looks to me like you have VLAN
> tags enabled on the VIF device in dom0, which means that the guest will
> see frames without the VLAN headers.
> 
> VLAN offload on the VIF would only matter if you were using trunk ports
> on the vswitch, which I don't think you are. (Although your
> configuration was a bit hard to read due to being posted as HTML and
> then mangled somewhere along the line).
> 
> Ian

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