RE: [Xen-users] XEN - Broadcom issue: survey

[S Senator <sts@xxxxxxxxxxxxxxxxxxxxxx>]

We have seen similar problems on Xen 2 (based on NetBSD 3.01) and Xen  
3.0.3 (based on Fedora 7).  It does not appear on Xen 3.0.3 on Debian  
Etch.
A work-around appears to be to transfer files in smaller fragments or  
smaller block sizes. For example, we see this repeatedly when NFS  
mounting from a central NAS server to domU's. By using UDP rather than  
TCP, this problem occurs much less frequently. It appears to be a  
protocol buffer problem between the bridge and TCP layers on the  
emulated network. It does not appear on native NetBSD, Fedora7 or  
Debian systems.
-Steve Senator
 sts+xen@xxxxxxxxxxxxxxxxxxxxxx


Quoting Boudreau Luc <luc.boudreau@xxxxxxxxxxxx>:

> A bit more information on this issue. We decided to buy another NIC   
> (other than Broadcom). The part number is NC110T from HP. It's an   
> Intel gigabit server NIC. The problem still happens, thus   
> eliminating the NIC problem. The card has the latest firmware and   
> the latest drivers (e1000 ver. 7.6.9.1-1).
> The problem is still happening when we transfer large files through   
> a domU->External. It doesn't happen when transferring   
> dom0->External. It is not a simple tcp_timewait issue since the   
> problem doesn't resolve itself after the tcp timeout.
> Is there anything I can test from me new setup that would help investigate ?
>
> ______________________________________________________
>
> Luc Boudreau
> Registrariat, Université de Montréal
>
>
> -----Message d'origine-----
> De : xen-users-bounces@xxxxxxxxxxxxxxxxxxx  
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] De la part de Pezza
> Envoyé : 15 novembre 2007 21:44
> À : xen-users@xxxxxxxxxxxxxxxxxxx
> Objet : Re: [Xen-users] XEN - Broadcom issue: survey
>
>
> Steven,
>
> thank you for your suggestions.
>
>
> Steven Smith-9 wrote:
> > vifX.Y interfaces are only used to send packets to PV network devices
> > in the guest.  Pure HVM domains (those without any PV drivers) send
> > all packets over the relevant tapX interface instead.  Errors observed
> > on the vif interface are therefore completely irrelevant in this case.
> > If the tap device has nothing strange then you'll have to look
> > somewhere else.
> Ok that's a very good hint.
>
> So far, this is the status:
>
> Steven Smith-9 wrote:
> > -- Do you see the same problems with dom0<->domU networking?  If so,
> > it would be a good idea to fix that before worrying about problems
> > with the NIC.  Packets which don't need to leave the host don't touch
> > the physical hardware.
> Dom0<->DomU is showing the same problem and, yes, you're right: probably
> it's not a network card related issue at this point...
>
>
> Steven Smith-9 wrote:
> > -- I understand you're seeing connections stall for significant
> > periods of time, and that this happens across a wide variety of
> > services, yes?  It would be interesting to know if other connections
> > to the same VM continue working when this happens.
> Yes they do.
>
>
> Steven Smith-9 wrote:
> > -- Is there a firewall enabled in the guest?  Turning it off might
> > help.  The dom0 firewall might also be relevant, although that's less
> > likely.
> I disabled firewalling in Dom0 and in DomU to take it out of the loop.
>
> I tried again with another machine (which is running Xen 3.0.4), and, on the
> same network (which is a gigabit network), it works fine. It's slow of
> course (no PV), but there's no corruption and it's stable.
>
> I'm willing to try to uninstall Xen 3.1 and try with 3.0.3 (the current Xen
> release for CentOS 5), maybe there is something else hidden somewhere in the
> background.
>
>
> M.


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