Re: [Xen-devel] Save/Restore is not working properly

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On Wed, Aug 10, 2016 at 12:11 PM, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
> On Sun, Aug 07, 2016 at 07:51:14PM +0430, Cendrin Sa wrote:
>> Hi,
>> I was searching a way to clone a machine using both memory and disk
>> approach.
>> I checked xen save/restore but after restoring, I can only work some
>> seconds with my machine and it will crash with the_kernel_task_hang_up.
>> using an script* to clone a machine is not working either.
>> so is it a bug or something or I'm cloning the wrong way?
>
> Hello,
>
> I've not tried to perform cloning myself, but I have a little script to
> perform VM checkpoints (so that you can restore the VM to any given point in
> time). It's based on FreeBSD so it uses ZFS, but it should work with LVM
> also if you replace it with the appropriate runes. AFAICT it should be quite
> easy to expand it to also do VM cloning. This is transparent from a VM point
> of view.

FWIW on a recent version of Xen-unstable, "xl save -c" appears to be
broken, at least with me CentOS 6 VM.  If I do "xl save" then "xl
restore", everything works fine; but if I do "xl save -c", then the
save appears to work as normal, and after it's done the guest console
has output similar to the output it has when restoring, but processes
which access the disk hang, and in 2 minutes I get "hung process"
output as Cendrin described.

I do get some warning messages though:

Using NULL legacy PIC
WARNING: g.e. still in use!
WARNING: leaking g.e. and page still in use!
WARNING: g.e. still in use!
WARNING: leaking g.e. and page still in use!
WARNING: g.e. still in use!
WARNING: leaking g.e. and page still in use!
Changing capacity of (202, 0) to 4194288 sectors

This is the stock CentOS 6.6 kernel: 2.6.32-504.16.2.el6.x86_64

 -George

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