Xen users - Apr 2009 - Slow Network Performance on GPLPV 9.12-pre13

I''ve got a Windows 2003 32 bit virtual running on Xen 3.3.1, with dual
Quad Intel Xeon E5345@2.3Ghz.  I''m having trouble getting more than a
few Mbps out of the system.  The drivers say that I''m running Xen-Net,
not the Realtek.  The PV drivers seem happy for the hard drives on the
system as well.  I''ve got ioemu removed from the vif line.

Any suggestions?


Thanks,
pace


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Addtional info, I''ve installed another Windows 2003 32 bit virtual with
GPLPV 9.12-pre13 and it is having the same issue.  Dom0 has no problem
getting hundreds of megabits from the network.  Linux DomU has no
problem getting hundreds of megabits either.


pace

Mark Pace wrote:
> I''ve got a Windows 2003 32 bit virtual running on Xen 3.3.1, with
dual
> Quad Intel Xeon E5345@2.3Ghz.  I''m having trouble getting more
than a
> few Mbps out of the system.  The drivers say that I''m running
Xen-Net,
> not the Realtek.  The PV drivers seem happy for the hard drives on the
> system as well.  I''ve got ioemu removed from the vif line.
>
> Any suggestions?
>
>
> Thanks,
> pace
> ------------------------------------------------------------------------
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users

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> 
> I''ve got a Windows 2003 32 bit virtual running on Xen 3.3.1, with
dual
Quad
> Intel Xeon E5345@2.3Ghz.  I''m having trouble getting more than a
few
Mbps out
> of the system.  The drivers say that I''m running Xen-Net, not the
Realtek.
> The PV drivers seem happy for the hard drives on the system as well.
I''ve got
> ioemu removed from the vif line.
> 
> Any suggestions?
> 
How are you testing performance? And are you measuring from DomU->Dom0
or DomU->external host?

If the latter, then your network adapter may not support TCP task
offload (checksum / large send), although if that was the case I would
expect that your performance would be kbits not mbits...

James


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> How are you testing performance? And are you measuring from DomU->Dom0
> or DomU->external host?
>
>   
Copying to and from a SMB share, I''ve tried the following at this
point:

DomU->DomU on same host, speed is good both copying to and from the share.
DomU->External Hosts, copying from the share to the DomU is good,
copying to the share is really slow.

So I tried FTP and SCP instead of SMB traffic:

DomU->DomU on same host, speed is good both directions
DomU->External Host, speed is good both directions

Something strange is afoot...
> If the latter, then your network adapter may not support TCP task
> offload (checksum / large send), although if that was the case I would
> expect that your performance would be kbits not mbits...
>
>   
Definitely have TCP offload on these machines.  Built in Intel Gigabit
connectors on Supermicro motherboard.

The condition is the same across the three different 2003 DomUs I have
on this host.  I do have another host around that I can move one of
these DomUs onto to see what happens there.


pace

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> > How are you testing performance? And are you measuring from
DomU->Dom0
> > or DomU->external host?
> >
> >
> Copying to and from a SMB share, I''ve tried the following at this
point:
> 
> DomU->DomU on same host, speed is good both copying to and from the
share.
> DomU->External Hosts, copying from the share to the DomU is good,
> copying to the share is really slow.
> 
> So I tried FTP and SCP instead of SMB traffic:
> 
> DomU->DomU on same host, speed is good both directions
> DomU->External Host, speed is good both directions
> 
> Something strange is afoot...
> 
> > If the latter, then your network adapter may not support TCP task
> > offload (checksum / large send), although if that was the case I
would
> > expect that your performance would be kbits not mbits...
> >
> >
> Definitely have TCP offload on these machines.  Built in Intel Gigabit
> connectors on Supermicro motherboard.
> 
> The condition is the same across the three different 2003 DomUs I have
> on this host.  I do have another host around that I can move one of
> these DomUs onto to see what happens there.
> 
Just turn off checksum offload and large send offload in the DomU
(advanced properties of network adapter). See if that makes a
difference.

James

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> Just turn off checksum offload and large send offload in the DomU
> (advanced properties of network adapter). See if that makes a
> difference.
>
>   
That did the trick.  Does that mean that something is up with my host
not supporting TCP offload correctly or something is not set right on it?


pace


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> 
> 	Just turn off checksum offload and large send offload in the DomU
> 	(advanced properties of network adapter). See if that makes a
> 	difference.
> 
> That did the trick.  Does that mean that something is up with my host not
> supporting TCP offload correctly or something is not set right on it?
> 
I think that quite a few Linux network drivers don't support offload
correctly once you start using bridging or anything other than a plain
'ethX' interface.

Don't rule out a problem with the GPLPV drivers though... it's possible
I'm doing something incorrectly that some drivers can tolerate and some
can't. I can't think what though.

James

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