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

[Eugene Istomin <e.istomin@xxxxxxx>]

Jesse from OVS maillist said:

"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"

I go deeper in testbed VM vlans and find:

#ethtool -k vlan1002
tx-checksum-ip-generic: off
generic-segmentation-offload: off 
tx-nocache-copy: off
tx-checksumming: off

#ethtool -K vlan1002 tx on
Could not change any device features

Is linux have offload on vnet vlan interfaces like VXLAN currently have 
(http://lists.openwall.net/netdev/2013/02/16/2)?

-- 
Best regards,
Eugene Istomin



On Friday, May 31, 2013 09:46:10 AM Ian Campbell wrote:
> On Fri, 2013-05-31 at 11:18 +0300, Eugene Istomin wrote:
> > 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?
> 
> I'd have expected the second case to be lower overhead, which it is. I
> would expect the first case to be higher overhead, which it is, but it
> seems a lot higher than I would have handwavily expected -- I'm not sure
> why vlan offload on the vif device should matter to that extent.
> 
> Wei, what do you think of implementing vif offload on the netback vif
> devices? I don't necessarily mean over the wire protocol, although that
> might be worth investigating separately, just at the netdev interface --
> i.e. inserting the VLAN header into the ring as part of
> xen_netbk_tx_build_gops() processing or whatever?
> 
> Ian.

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