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Re: [Xen-users] Unable to create guest with more than 2gb of memory

  • To: "'Ian Campbell'" <ian.campbell@xxxxxxxxxx>, <xen-users@xxxxxxxxxxxxx>
  • From: "Marc Tousignant" <myrdhn@xxxxxxxxx>
  • Date: Thu, 8 Oct 2015 11:23:02 -0400
  • Delivery-date: Thu, 08 Oct 2015 15:23:34 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>
  • Thread-index: AQFfAGfjNFgGMlOyvWL/lVAKAHj1YgGbSTW1AgWM7hkDJDPMUwLcag4KAjNKAjqe5xAJoA==

-----Original Message-----
From: Ian Campbell [mailto:ian.campbell@xxxxxxxxxx] 
Sent: Thursday, October 8, 2015 10:21 AM
To: Marc Tousignant <myrdhn@xxxxxxxxx>; xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Unable to create guest with more than 2gb of memory

On Thu, 2015-10-08 at 09:56 -0400, Marc Tousignant wrote:
> > 
> # cat /etc/xen/W2k12SQLTest.cfg

Looks fine to me.

FWIW you can normally omit these ones unless you know you have specific cause 
to deviate from the defaults:
> shadow_memory = 8
> acpi = 1
> apic = 1

acpi+apic both default on and unless you have good reason to do so I
wouldn't recommend messing with shadow_memory.

(I mention this because a lot of people cargo cult these sorts of options from 
older versions of Xen etc).

> OK, now this is weird... All I did was run an xl create with -vvv and 
> now it is working. The error from the original email was from the same 
> guest without -vvv, that was the only change. I know this should not 
> have any effect on this.

Indeed not.

I'm inclined to say that if rebooting the host (whenever you get a chance) 
doesn't make the issue reappear then we put it down to gremlins. If it does 
cause it to reappear then we can investigate what -vvv is doing that shouldn't 
be gated on that.

To that end, if you reboot then collecting "xenstore-ls -fp" right after boot 
would be handy, for comparison with after "xl create" and after "xl -vvv 
create", since that's the most likely place I can think of where something 
"sticky" might happen.

> I stopped several of my other running VM's, modified their configs to 
> the higher ram I originally used them with and they are working now 
> too. I didnât even need to do the -vvv on them.
> All of the guests are widows based, several are Win7, one 2008 and one 
> 2012.

FWIW such guests do not support booting with maxmem>memory, unless you have PV 
drivers with PoD (populate-on-demand) installed. It doesn't look like you have 
that though. Windows domains cannot grow past their initial maxmem (whether 
maxmem=memory or maxmem>memory). maxmem defaults to memory.



Looks like we are going to have to go with gremlins.. Restart of the host and 
then doing a create right after, without -vvv all hosts started up with the 4gb 
or 8gb configs that previously caused them to fail. I'll take out the acpi, 
apci, shadowmem options per your recommendation later when I get home.



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