Re: Strange network behaviour

Dor Laor
2007-12-05T09:17:38Z

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Mike wrote:
> 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.
>
>
>
It might be related to swapping (the host swaps guest pages).
Please check the ram size used by the guest.

Can you re-run the test with a single test or with disabling the swapping?
Thanks,
Dor.
> 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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>
>
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