[ovs-discuss] Xen/OVS - VLAN offloading

Eugene Istomin e.istomin at edss.ee
Fri May 31 09:55:58 UTC 2013


Thank you,

i will continue this discussion in xen maillists.
-- 
*/Best regards,/*
/Eugene Istomin/



> On Fri, May 31, 2013 at 5:17 PM, Eugene Istomin <e.istomin at edss.ee> 
wrote:
> >> This is dependent on the hypervisor and not being restricted by OVS.
> >> However, the direct benefits of vlan offloading are very minimal and
> >> are really only useful in relation to enabling other offloads.
> > 
> > In my testbed results are not minimal (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?
> 
> You are seeing the result of TSO not functioning in the presence of
> vlans. This is one of the other offloads that I was referring to
> before but it's not directly the result of the features that you
> showed. Regardless, this is a limitation of Xen and not something that
> OVS affects.
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