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Re: [Xen-users] Network performance problem

To: Fridtjof Busse <fbusse@xxxxxx>
Subject: Re: [Xen-users] Network performance problem
From: James Wilson <jwilson@xxxxxxxxxxxxxxxxx>
Date: Wed, 19 Dec 2007 13:52:52 -0600
Cc: Ralf Kaestner <Ralf.Kaestner@xxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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I am having a similar issue I see the retransmissions and dup acks basically everything you are seeing. The 2 things that are different on my end is that I'm using centos5 and piranha(for a virtual failover IP). I see the duplicate and retranssmissions on eth1:1(the vip from piranha). Would the below fix for you also apply to me(ethtool -K eth0 tx off). Also would I apply this to the VIP? ethtool -K eth1:1 tx off?

Fridtjof Busse wrote:
* Ralf Kaestner <Ralf.Kaestner@xxxxxx>:
Has the guest enabled any TCP task offloading (if yes try turning it

You already gave me the right hint, without me noticing:
'ethtool -K eth0 tx off' in the domUs.
That immediatly fixed the problem. Thanks!
Question remains: Why does it fix the problem? I never had to do that
with kernel 2.6.18 (Xen 3.1.0) from XenSource.

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