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

[Richard Blocker <rblocker@xxxxxxxxxxxx>]

So, 24 hours plus one and something did reach out and bite me. I got
another 100% CPU usage and frozen guest HVM. This time there was no
prelink running.  Is full virtualization this full of bugs?

Richard Blocker wrote:
> Ahhh, (deep sigh of relief) this is good to know. Thanks for the
> response, Dan. I disabled prelink and the VM has been running great for
> 24 hours, but I was afraid something else might be lurking to reach out
> and bite me. I need the full virtualization for better security and
> portability in this instance, and performance has not been an issue (so
> far).
> 
> Rick
> 
> Daniel P. Berrange wrote:
>> 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.
> 
> 


-- 




Richard Blocker
Information Systems Manager
Ecology and Evolution
Organismal Biology and Anatomy
University of Chicago
Zoology 003
1101 E. 57th Street
Chicago, IL 60637
rblocker@xxxxxxxxxxxx
telephone: 773-702-5135
facsimile: 773-702-9740

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