Re: Strange network behaviour

Mike
2007-12-05T09:06:19Z

Hello Lynn,

I'm using a bridge, which is configured in my /etc/network/interfaces
like this:
auto br0
iface br0 inet static
address 195.24.77.169
netmask 255.255.255.0
gateway 195.24.77.1
bridge_ports eth0
bridge_stp off
bridge_maxwait 5

an I have a file called qemu-ifup in /etc which has the following content:
#!/bin/sh
/sbin/ifconfig $1 0.0.0.0 promisc up
/usr/sbin/brctl addif br0 $1
sleep 2

Every guest has it's own tap device, atm tap0 - tap4 are in use.
Those peaks are coming after +/- 10 mins (not always the same time,
sometimes after 5 mins, it changes). Within this time, the guests have
normal pings.

Lynn Kerby schrieb:
> 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)
>>
>> Reply from 195.24.77.170: bytes=32 time=36ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=123ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=98ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=116ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=241ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=72ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=382ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=135ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=397ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=647ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=857ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=1156ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=692ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=604ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=188ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=39ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=46ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=39ms TTL=57
>>
>> 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:
>>
>> Reply from 195.24.77.169: bytes=32 time=38ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=39ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=38ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=40ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=37ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.169: bytes=32 time=33ms TTL=57
>>
>> 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:
>>
>> Reply from 195.24.77.171: bytes=32 time=37ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=37ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=97ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=60ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=186ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=363ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=368ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=972ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=673ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=1133ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=1198ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=1881ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=2341ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=2401ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=2006ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=2638ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=3590ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=383ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.171: bytes=32 time=34ms TTL=57
>>
>> So I tried disabling kvm when starting a guest.
>> and here the guest *with* -no-kvm in the command line:
>>
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=36ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=36ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=37ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=38ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=35ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=37ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=33ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>> Reply from 195.24.77.170: bytes=32 time=34ms TTL=57
>>
>> 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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>
>
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