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

[Imre Oolberg <imre@xxxxxxxxxxx>]

Hallo!

..
> Is there any way to stop that module from loading without having to 
> modify the initrd?
dont know that, but actually just for sake of experiment it is not hard 
to make new ramdisk archive, for example like that for the running kernel
 bash# mkinitramfs -o /boot/ramdisk-20080705.img

and direct additional grub boot entry to use it.

In this way you could at least check how different drivers perform with 
your adapter. To look into ramdisk just unpack the archive
 bash# mkdir /tmp/ramdisk-20080705 && cd /tmp/ramdisk-20080705
 bash# gunzip -c ../ramdisk.img | cpio -dmvi

> Meanwhile, i've modified my xend-config file, setting dom0-cpus to 1 (it 
> was set to 0). Then i restarted the server, and so far so good. I'll 
> keep it running for several days and see what happens.
> The network adapter always works fine for some time when the system has 
> been restarted. And then, all of a sudden, it starts performing very 
> poorly, or it looses connection, having to reboot in order to get it 
> working again.
Somehow i think there is some kind of unluck going on around your 
motherboard and adapter and perhaps easiest workaround is just to get 
new ethernet adapter and life is good again! :)
Or as an experiment boot again your system up with an ordinary kernel 
and stresstest network adapter. For example flood some traffic thru it 
with hping3 and monitor how it performs with iptraf.
And last but not least, Xen system shows up for the local switch as 
multiple mac addresses behind the same switch port. Maybe it has 
something to do with it. If you can, use only single ip address and mac 
address in association with that adapter. I.e. in dom0 leave the ethx's 
ip addres unconfigured and configure its ip address only in domU.
Also, perhaps you could load ethernet adpater module with some arguments 
or tweak something with ifconfig i.e. media options. With ethtool -s you 
could also change media options like speed, maybe it changes it somehow 
by itself.
And in ifconfig output look at the errors
...
RX packets:132854764 errors:0 dropped:0 overruns:0 frame:0
TX packets:133486462 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0

I am quite ordinary computer user, thats about all what i could possible 
help on this one, some network or xen hard core is of more help most 
probably. And good luck!

Imre

PS I have old good asus a8n-sli premium motherboard which has lost by 
now almost everything but its name, i.e. onboard sata ports start giving 
errors after running some weeks and also onboard ethernet adapters stop 
working. At the same time ethernet adapters as pci card work correctly 
although sometime they agree with switch on wrong speed.
> Best regards,
> Alex
>
> 2008/7/5 Imre Oolberg <imre@xxxxxxxxxxx <mailto:imre@xxxxxxxxxxx>>:
>
>     Hi!
>
>     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
>     firmware-version:
>     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,
>
>     Imre
>
>
>
>     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!,
>         Alex
>          2008/6/23 randall ehren <randall@xxxxxxxxxxxxx
>         <mailto:randall@xxxxxxxxxxxxx> <mailto: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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