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


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!


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,

2008/7/5 Imre Oolberg <imre@xxxxxxxxxxx <mailto:imre@xxxxxxxxxxx>>:


    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> <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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