Re: Strange network behaviour

Lynn Kerby
2007-12-05T07:53:11Z

Hi Mike,

Glad to hear that your networks are up now, but what are you using to
connect/bridge them? Those response times are horrible across the
board!

All my VMs are connected to my internal network via a bridge on the
host through their tap interfaces and a few lucky machines share
another bridge that is on my DMZ with static IPs. I think the
network bridge method I use is based on some stuff I picked up a few
years ago when working with the UML virtualization stuff. I see sub
millisecond ping responses in both directions and to all VMs (usually
I've got 3 or 4 active, soon to expand to a few more).

My HOST config is similar though I've got a only 4GB of memory and
I'm still running KVM-52 modules. My guests are Ubuntu 7.10, Fedora
8, and FreeBSD 6.2 at the moment with Mint4.0 and JeOS on the drawing
board.

Lynn Kerby
San Martin, CA

On Dec 4, 2007, at 2:44 PM, Mike wrote:

> Hello,
> I already spoke to Izik Eidus. He told me to publish the results to
> the
> problem at the mailinglist.
>
> Some time ago I wrote to the kvm-devel mailinglist that I had a
> problem
> with my guests' networking dying.
> I got the hint to change the network card emulation. That worked.
>
> Now I noticed a strange behaviour.
> I have a gameserver running in a guest os. No problems on performance
> side, really fast.
> The only thing, when I make a ping test after unspecific time
> periods I
> get this: (this peaks are even there if the gameserver isn't running)
>
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>
> This ping peaks are on *all* guests I'm currently running.
> I did a ping test the same time to the Host, with this result:
>
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>
> As you can see, no peaks.
> Example of start command from a guest:
> kvm -hda apache.img -hdb apache_storage.img -m 512 -boot c -net
> nic,vlan=0,macaddr=00:16:3e:00:00:01,model=rtl8139 -net tap -nographic
> -daemonize
>
> Here the pings from the guest started with the command line listed
> above:
>
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>
> So I tried disabling kvm when starting a guest.
> and here the guest *with* -no-kvm in the command line:
>
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>
> The other guest, without -no-kvm have the ping peaks. Also here, no
> ping
> peaks from the host.
> Server load is really really low at the moment of the tests.
>
> Maybe you have an idea where this peaks are coming from?
> I'm using KVM-55 on Ubuntu 7.10 server with Kernel Linux A050
> 2.6.22-14-server #1 SMP Sun Oct 14 22:09:15 GMT 2007 x86_64 GNU/Linux.
> My CPU is an AMD Athlon 64 X2 5600+ (Dual Core) with 8GByte of RAM.
>
> Greetings from Luxembourg.
> Mike Weimichkirch
>
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