Re: [Xen-users] PCI passthrough, poor network performance in upload direction

["Luis F Urrea" <lfurrea@xxxxxxxxx>]

Guest kernel is: 

2.6.18.8-xen

This is a paravirtualized Debian installation on the guest booted with PyGrub

NICs are both:

Broadcom NetXtreme BCM5722 Gig Ethernet PCI Express

System:
AMD Opteron 2212 2GHz
4 GB RAM
on Dell Poweredge T105

DomU's 512 MB RAM

Driver is tg3 compiled from source on guest domain.

Thanks for your help!

On Thu, Dec 11, 2008 at 2:20 PM, Todd Deshane <deshantm@xxxxxxxxx> wrote:

On Thu, Dec 11, 2008 at 4:10 PM, Luis F Urrea <lfurrea@xxxxxxxxx> wrote:
> Hi all,
>
> I have been having an issue for over a year with several Xen installations
> and have not been able to find out if this is just something I am missing.
>
> Basically I am trying to configure a firewall with two ethernet cards in a
> domU using pci passthrough. I am hiding the Ethernet cards at boot time via
> the pciback.hide kernel option.
>
> Right now I am running Xen 3.3.0 and the two Ethernet cards are passed to
> the FW domU.
>
> The FW domU is not configured with a vif interface to the bridge, so
> basically communication with DomO passes through the external hardware.
>
> Tests using iperf show me that download bandwidth from the FW domU to an
> external machine connected to the switch go as high as 94 Mbits/sec. However
> upload bandwidth from a laptop to the domU give me a maximum of 574
> Kbits/sec which basically is not enough to cover the upload bw of some
> internet connections.
>
> I have read recommendations about using ethtool -K ethX tx off in dom U, but
> in this case the tx ring does not seem the be the issue since the download
> speeds are just fine. Using 'ethtool -K rx eth0 off' did not show any
> improvements.
>
> Since the guest domain has exclusive access to both Ethernet cards I suppose
> that the overhead is introduced somewhere in the domU's kernel but I
> wouldn't exactly know where else to look for a possible fix.
>
> Your input is appreciated.
>

What is your guest kernel?

Is this all PV?

What is your hardware (both NIC and system)?

What driver is the guest using for the device?

Cheers,
Todd

--
Todd Deshane
http://todddeshane.net
http://runningxen.com

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