Re: [Xen-devel] Memory allocation with rebooted HVM

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 13 Oct 2009, John wrote:
> Stefano,
> 
> Thanks for posting.
> 
> > Could you please post the log of what happened right before?
> > .From that it should be clear if the destruction of the old guest or
> > stubdom didn't go smoothly.
> 
> Here are the entries before what I gave before, starting with an old line 
> that was unrelated (afaik):
> 
> [2009-10-11 13:14:50 6419] INFO (image:586) testvds device model terminated
> [2009-10-11 14:23:17 6419] INFO (XendDomainInfo:1961) Domain has shutdown: 
> name=testvds id=19 reason=reboot.
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2844) 
> XendDomainInfo.destroy: domid=19
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2279) Destroying device 
> model
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2286) Releasing devices
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2292) Removing vif/0
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = vif, device = vif/0
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2292) Removing console/0
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = console, device = console
> /0
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:2292) Removing vbd/768
> [2009-10-11 14:23:17 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = vbd, device = vbd/768
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:2292) Removing vbd/5632
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = vbd, device = vbd/5632
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:2292) Removing vbd/5696
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = vbd, device = vbd/5696
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:2292) Removing vfb/0
> [2009-10-11 14:23:18 6419] DEBUG (XendDomainInfo:1185) 
> XendDomainInfo.destroyDevice: deviceClass = vfb, device = vfb/0
> [2009-10-11 14:23:19 6419] DEBUG (XendDomainInfo:121) 
> XendDomainInfo.create_from_dict({
>


.From these logs it seems that the destruction of the old guest went
fine but the old stubdom is still alive.

> > Are you sure that this is a stubdom specific issue?
> 
> I didn't see problems like this before I switched to using stubdoms a few 
> days ago, but back then, I was also using a dom0 with ballooning, which 
> might have affected things (when I switched to stubdoms, I also set dom0_mem 
> to 512M).
> 
> > Because from the logs it seems that your host ran out of memory.
> > For example, were you trying to start another guest while rebooting the
> > first one?
> 
> This seems to have been triggered just by that one domU being restarted. 
> I've seen this before as well, when a 4G domU tried to restart and hosed a 
> box that only had 3G of memory free (on top of the 4G it was using).

It seems to me that the new domain is always created after the old one
has been destroyed with the exception that the old stubdom may still be
alive but one stubdom uses only 32MB of ram, therefore cannot be the one
preventing you from restarting the domain, especially in the case above
where you had 3G free.

Maybe someone else more confident with xend memory managent can comment
on this.


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