Re: [Xen-users] RHEL6 domU migrate issues w/ higher to lower frequency CPU's

[Joshua West <jwest@xxxxxxxxxxxx>]

Hi Paras,

In what way does your migration fail?  Does it succeed but then the 
virtual machine is then completely unresponsive, including the console?  
Or does the migration just error/exit out?
I've heard reports of problems like this with the stock RHEL 5.x Xen 
software, regardless of CPU MHz clock speed, having issues.  In my case, 
it only seems to be a problem when moving from servers with 
higher/faster CPU MHz clock speeds to those with lower.  Also, it now 
looks like the console finally becomes responsive after about 5-10 
minutes of being hung up.
I've opened a case with Red Hat as well:  
https://bugzilla.redhat.com/show_bug.cgi?id=663755
I'm interested to see if this is the same bug you and I are experiencing 
or if its two different issues, as I'm running a later version of Xen.
Thanks for the input!

On 12/16/10 10:40, Paras pradhan wrote:
> I am having exactly the same problem. Plus this bug is seen when you
> have the same cpu in both nodes too. I have tested in Quad-Core AMD
> Opteron(tm) Processor 8374 HE in both nodes and same problem.
>
> Symptoms:
>
> * Start the node in node1. No problem
> * Live migrate to Node2 (same cpu, 100% same hardware). domU
> unresponsive, no output in xm console, can ping ,can see ssh banner
> but dead slow
> * Migrate back in node1, No problem
>
> I could reproduce this problem in another set of systems too. Same problem.
>
> I have a ticket opened with Redhat from around 2 weeks. no help till now.
>
> Also I have seen this bug filed at Redhat but dunno if they are
> working on it or not.
> https://bugzilla.redhat.com/show_bug.cgi?id=613513
>
> This is really frustrating.
>
> Paras.
>
>
> On Wed, Dec 15, 2010 at 5:03 PM, Joshua West<jwest@xxxxxxxxxxxx>  wrote:
> > Hey folks,
> >
> > I've encountered a rather interesting/frustrating issue with RHEL6 domU's
> > and live migration.
> >
> > I have no problems booting a RHEL6 domU using its stock/native kernel on Xen
> > 3.4.1 or Xen 3.4.3.  But in terms of live migration, there seems to be a
> > problem when moving from a higher (in terms of CPU MHz) to lower (MHz)
> > system -- even if the higher of the two is a much older CPU model.
> >
> > For example, I can reproduce the bug under Xen 3.4.3 with the following:
> >
> >   * Migrating from X5450 @ 3.00GHz to X5355 @ 2.66GHz fails, but the opposite
> > (increasing in CPU frequency) succeeds.
> >   * Migrating from Xeon(TM) CPU 2.80GHz to E5310 @ 1.60GHz fails, but the
> > opposite (increasing in CPU frequency) succeeds.
> >
> > BTW, when I say "fails", what I really mean is the migration succeeds but
> > the domU is no longer responsive.  I can attach to the console via 'xm
> > console' but nothing is displayed, although occasionally a new line is
> > printed as i bang my hands on the Enter key.  Occasionally ping works and
> > occasionally I can establish a connection to the domU's port 22 and see the
> > OpenSSH banner, but thats as far as I get.  Its not like the domU is runaway
> > with 100% cpu.  It sits with state "-b----" (xm list).
> >
> > I have tested cpuid masking but this doesn't help.  Its an issue with going
> > from a higher CPU frequency system to a lower CPU frequency system.
> >
> > This is using the stock RHEL6 kernel 'vmlinuz-2.6.32-71.7.1.el6.x86_64'.
> >
> > Anybody have suggestions on the cause or a workaround?  Experience this
> > issue too?
> >
> > I've heard through the grapevine that this bug is also confirmed with RHEL6
> > domU's on XCP 1.0.
> >
> > Thanks for any help you can provide!
> >
> > --
> > Joshua West
> > Senior Systems Engineer
> > Brandeis University
> > http://www.brandeis.edu
> >
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
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--
Joshua West
Senior Systems Engineer
Brandeis University
http://www.brandeis.edu


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