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Re: [forums] RE: [Xen-users] Re: domU network fails under load - vif bre

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Subject: Re: [forums] RE: [Xen-users] Re: domU network fails under load - vif breaks
From: Paul <xensource@xxxxxxxxxxx>
Date: Sat, 06 Sep 2008 12:50:52 +1000
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Hi Nathan,

Yeah, this was something I was wondering about too... The driver change was from the kernel driver to the manufacturers own driver - but I imagine it leverages off code in the kernel in any case.

I am testing a tulip based 10/100 card at the moment, and pushing it pretty hard without any issues. This isn't a one for one test yet, as I have my other domains off the original nic, but it certainly looks promising.


Nathan Eisenberg wrote:

I'm wondering if #3 is a large enough change to rule out driver issues. Maybe try an entirely different chipset and manufacturer - perhaps an Intel, Broadcom, etc NIC.
Thank you,
Nathan Eisenberg
Sr. Systems Administrator
Atlas Networks, LLC

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Paul
Sent: Thursday, September 04, 2008 3:43 PM
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Re: domU network fails under load - vif breaks

On Sep 1, 2008, at 8:57 AM, Paul wrote:

    At a certain point that I have not established exactly, the
    network load takes out the pv network. For example, if I initiate
    a bittorrent session in a pv domU, I get a slow build up of
    network load, and then connectivity is lost to both of the pv
    domU's. If I console into them, they cannot ping outside the
    network, but they can ping their own interfaces. A tcpdump on the
    dom0 physical shows no traffic. However, during all this, the hvm
domains are able to use their network connections without issues. I have experienced the same issue with Ubuntu 8.04. The only solution I have found is to limit the rate of the nic so that it doesn't reach a transfer rate that breaks the networking.
Thanks Pepe. My last test showed the network breaking at 3.6Mbs - too slow to lower the nic rate, and having networking running that slow would make the vm unusable for its purpose.

I have upgraded Xen from 3.2.1 to 3.3, and the problem remains, which means I have changed:

1) Change domU kernel (2.6.21, 2.6.24, 2.6.25)
2) Change domU userland (gentoo, ubuntu)
3) Change dom0 physical nic + driver (Realtek 8169 -> 8168)
4) Change Xen version (3.2.1 -> 3.3)

The only thing I haven't changed is the dom0 kernel. I am using a stock 2.6.21-xen gentoo kernel, so it would be great if anyone watching this that has pv domUs working under a 2.6.21 kernel would post their .config so I can compare it to mine.



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