RE: [Xen-users] Lots of udp (multicast) packet loss in domU

["Venefax" <venefax@xxxxxxxxx>]

I pinned one application to one processor and the quality jumped
dramatically. I wish to understand the second fix proposed by James. The
checksum offloading. What is that exactly? 

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of James Harper
Sent: Monday, January 12, 2009 7:52 PM
To: Mike Kazmier; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] Lots of udp (multicast) packet loss in domU

> Hello,
> 
> After a few of us have spent a week google'ing around for answers, I
feel
> compelled to ask this question: how do I stop packet loss between my
dom0
> and domU?  We are currently running a xen-3.3.0 (and have tried with
xen-
> 3.2.1) on a Gentoo system with 2.6.18 kernel for both domU and dom0.
We
> have also tried a 2.6.25 kernel for dom0 with exactly the same
results.
> 
> The goal is to run our multicast processing application in a domU with
the
> BRIDGED configuration.  Note: we do not have any problem if we put the
> network interfaces into PCI Passthrough and use them exclusively in
the
> domU, but that is less than ideal as occasionally other domU's need to
> communicate with those feeds.
> 

Googling has probably already lead you to these tips but just in case:

Try 'echo 0 > bridge-nf-call-iptables' if you have't already. This will
stop bridged traffic traversing any of your iptables firewall rules. If
you are using ipv6 then also 'echo 0 > bridge-nf-call-ip6tables'

Another thing to try is turning off checksum offloading. I don't think
it is likely to make much difference but due to the little effort
required it's probably worthwhile. (ethtool -k to see what settings are
on, ethtool -K to modify them)

Also try pinning Dom0 and DomU to separate physical CPU's. Again I don't
think this is likely to make much difference but it's easy to test.

Please post back with what you try and what sort of difference it makes,
as I'm always on the lookout for ways to improve network performance.

James

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