Re: [Xen-users] apparently random lockups

["Eric S. Johansson" <esj@xxxxxxxxxx>]

Eric S. Johansson wrote:
> I'm using xen unstable taken from hg repository a couple of days before 
> 3.0 release (how's that for timing).
> I've been struggling with a series of random lockups on a domU I'm using 
> as a mailserver.  the initial problems were that any significant 
> activity either on the mail server or the IMAP server would cause the 
> domU to go dead with absolute no information in the log files or console.
now that I've had some sleep, here's a little bit more information.  It 
looked like at all the lockups were focused on one particular domU 
instance.  when I woke up, a different domU instance was "dead".  it was 
not responding to connections over its ethernet interface.
I connected to the console and found I could login. ifconfig showed that 
the interface was up and had an IP address.  But I could not go out to 
that interface to any other machine.  Restarting the virtual machine 
brought the interface back to life.
I think I'm tripping over a series of bugs and getting confused. 
Teasing apart my experience, I would say that I hit two bugs definitely 
and the feeling that there are more can be chalked up to paranoia.
Bug 1: dual mounting an LVM partition creates excessively high load 
averages in a domU instance.  By dual mounting I mean mounting the 
partition in dom0 as well as one domU instance.
even though the load average climbs within the domU, there is no 
indication of that load climbing from the outside with xm top.
to reproduce, mount one lvm partition in both dom0 and a domU.  run some 
disk intensive process like a recursive grep on the partition in the 
domU.  Load average should climb within a couple of minutes and was 
unstoppable by my experience.

bug 2: ethernet interfaces go dead.  it only seems to happen on one domU 
at a time but seems tied to ethernet activity level.  You should be able 
to log in via the console and shut down the domU machine.  This is much 
harder to reproduce but I suspect some form of rapid or intense ethernet 
activity should trigger it.
I suspect both of these problems are easier to reproduce on a slow 
machine (i.e. Pentium III 500) like the one I'm using.  ;-)
---eric

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