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RE: [Xen-users] Stability of XEN under high load

To: "'Thomas Goirand'" <thomas@xxxxxxxxxx>
Subject: RE: [Xen-users] Stability of XEN under high load
From: "Venefax" <venefax@xxxxxxxxx>
Date: Mon, 1 Dec 2008 07:01:51 -0500
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
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How often do you run this script?

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Thomas Goirand
Sent: Monday, December 01, 2008 6:41 AM
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Stability of XEN under high load

> On Sun, Nov 30, 2008 at 12:13 AM, Bernd Gotschy
> <Bernd.Gotschy@xxxxxxxxxxxxxx <mailto:Bernd.Gotschy@xxxxxxxxxxxxxx>>
>     Major problem is  that under high load we loose some of the network
>     interfaces and cannot get them working unless we reboot the guest.

We have find out quite the opposite way. If one of the VM has no
activity, the ARP vs IP cache of most switch will discard the MAC of the
VMs. So we have made a very simple python script that we deploy on all
of our Xen servers, that simply does a ping of all VMs it finds in the
/etc/xen/auto folder. This way, the ARP cache gets refreshed, and
everything is working fine. Maybe this is what you are experiencing, no?
Anyway, bellow is the script, I hope that helps (take care, the procs =
line might appear on 2 lines as I didn't do an attachment).


#!/usr/bin/env python

import glob
import re
import subprocess
import os
import sys

pathspec = "/etc/xen/auto/*"
regexp = re.compile(r"vif.*?=.*?ip=([0-9\. ]+)'")

files = glob.glob(pathspec)

contents = ( file(t).read(-1) for t in files )

def ips(contents):
        matches = regexp.findall("\n".join(list(contents)))
        for match in matches:
                mips = match.split(" ")
                for ip in mips: yield ip

devnull = file("/dev/null","w")
procs = (
for ip in ips(contents) )

returncodes = ( proc.wait() for proc in list(procs) )


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