Re: [Xen-users] Re: Xen guest domain freezes when prelink runs

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Thu, Jun 21, 2007 at 08:33:51PM -0400, Tim Boyer wrote:
> On Thu, 21 Jun 2007 09:09:39 -0500, Richard Blocker <rblocker@xxxxxxxxxxxx>
> wrote:
> 
> >I'm new to running Xen, so maybe I missed something, but this is a
> >puzzling problem that I didn't find on any of the Xen lists.
> >
> >I'm running the Xen 3.0.3 that comes with RedHat EL 5 (all stock, all up
> >to date as of today) and I have a single guest domain HVM also running
> >RHEL 5. Whenever the guest OS runs the initial prelink job defined in
> >/etc/cron.daily (/usr/sbin/prelink -av -mR -f) the guest CPU pegs at
> >100% and the system stops responding. It never resumes (at least not for
> >12 hours). I can reboot the guest domain from the host machine, and it
> >recovers fine, until prelink runs. I even ran cpu-burnin on the HVM to
> >see if it was just the load, but it was fine while that ran.  If I run
> >the prelink command manually, it immediately freezes.
> >
> >For the record, the hardware is a dual quad core Xeon system with 8GB of
> >memory.  The guest HVM uses a single CPU with 512MB of memory allocated.
> >
> >Has anyone else seen this?
> 
> Hah!  Someone else with this...
> 
> I've got a trouble report into RH on this one.  It's not just prelink; I think
> it's tied to rpm.  I can bring the system down doing a rpm -Va, or a sysreport
> without the -norpm switch.  Also a dual quad core, with 16gb, and 1gb on the
> guest.

Actually it is prelink - rpm -Va will call out the prelink libraries when
verifying IIRC.  Anyway, this is ultimately a hypervisor bug in Xen 3.0.3
which should be fixed in the Xen 3.1.0 hypervisor. So should be working
come RHEL-5.1  updates.  

Seriously though, you really really really don't want to run any OS in
full-virt if its capable of paravirt. You'll get x10 -> x100 the I/O
performance if you use paravirt and be able to scale up the number of
guests per host much better. So I'd recommend using RHEL-5 paravirt
at which point you won't see the HVM bug anymore either...

Dan.
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