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Re: [Xen-users] Poor network performance on Dom0 [2.6.18-6-xen-amd64]

To: Alejandro Martini <alejandro.martini@xxxxxxxxx>
Subject: Re: [Xen-users] Poor network performance on Dom0 [2.6.18-6-xen-amd64]
From: Imre Oolberg <imre@xxxxxxxxxxx>
Date: Sat, 05 Jul 2008 14:15:58 +0300
Cc: xen-users@xxxxxxxxxxxxxxxxxxx, randall ehren <randall@xxxxxxxxxxxxx>
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If it helps but i found out which driver is associated with my p/ethx devices running ethtool like this

aix:~# ethtool -i peth1
driver: r8169
version: 2.2LK-NAPI
bus-info: 0000:06:09.0

And to make sure wrong driver isnt getting in the way i sometimes just removed it from module tree under /lib/modules/... (or ramdisk i.e. initrd image) though there is obviously more appropriate way doing it.

I also run the same software and only thing which made it unstable was having multiple cpu's in dom0 but it is know fact and workaround is to have in /etc/xen/xend-config.sxp

# In SMP system, dom0 will use dom0-cpus # of CPUS
# If dom0-cpus = 0, dom0 will take all cpus available
(dom0-cpus 1)

Best regards,


Alejandro Martini wrote:
Randall, thank you for sharing those tips. The network card was working fine on this system before installing Xen. At least i've never noticed any problems like the ones i reported while i was setting up the base system (Debian Etch, via netinstall).

Now i think that the problem might be related to the fact that Xen is not loading the right module for this network adapter. I've googled around quite a bit, but wasn't able to find a conclusive statement on what kind of card this is.

There are at least three possibilities, since:

- The manufacturer states that this is a Realtek RTL8111B (the motherboard is an ASRock AliveNF5-eSATAII) - lspci identifies it as "Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller"
- udev seems to have detected it as 8169
- Xen loads the r8169 module for this card, even if r8168.ko is present and r8169 is blacklisted.

So, i cannot tell for sure if i'm dealing with an 8169, an 8168B or an 8111B.

If i run modinfo, i can see that both modules (r8168 and r8169) have matching aliases for this card type (10ec:8168), and then i don't really know how the kernel decides which module to load, or how to tell it to choose one over the other.

With regard to your other advice (installing irqbalance), the latest known version for debian/stable is 0.12-7. I guess that it's pretty outdated. Anyway, if you think that it's worth trying, i'll install it and see what happens.

Thanks again!,
2008/6/23 randall ehren <randall@xxxxxxxxxxxxx <mailto:randall@xxxxxxxxxxxxx>>:
 > two things i can think of:
> 1) did you ever test this machine's networking performance before installing xen?
> 2) have you tried installed 'irqbalance'? i've had to install that on dell 2650's running xen 3.0.x
 > -randall


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