[Fedora-xen] Can't allocate memory (12)

Wed Nov 22 17:06:53 UTC 2006

I need to make a clarification.  This is not only applied to Windows Guest
OS.  If all the "Physical" memory has assigned to Dom0, I can't add any
Fully virtualized Guest OS.

I got "virDomainCreateLinux() failed' from virt-manager or Can't allocated
memory error from shell ( xm create -c win2k3 )

Paravirtualized Guest OS is fine but like I said I can't find a way to
create a Windows Paravirtualized Guest OS.

             Barrow H Kwan                                                 
             <bhkwan at thoughtwo                                             
             rks.com>                                                   To 
             Sent by:                  "Daniel P. Berrange"                
             fedora-xen-bounce         <berrange at redhat.com>               
             s at redhat.com                                               cc 
                                       fedora-xen at redhat.com               
                                                                   Subject 
             11/22/2006 08:42          Re: [Fedora-xen] Can't allocate     
             AM                        memory (12)                         

here are more information about the issue

When all memories are allocated to Dom0, I can add Paravirtualized Guest OS
but this limited to Linux OS ( I mean I don't know if it is possible to run
Windows as a Paravirtualized VM ).  If I tried to add a FULLY Virtualized
Guest OS, I will get this error.   To fix this, I have to change the memory
for Dom0 ( under Grub ).   I have a 16G box and when I assigned 14G to the
Dom0, then I can add a Fully Virtuallized Windows Guest OS with 1.5G
memory.   When I tried to add another Windows Guest OS with 1G memory, I
got the same memory error again.

My guess is the number of fully virtualized Windows Guest OS I can run will
depend on the "phyical" memory that I have.   for example, if I have a 16G
box, if I allocate 4G memory for a Windows Guest OS, I can only run 4 of
them ( ie 4 x 4G = 16G ).  Unless this is a problem with the FC6's Xen.

             "Daniel P.
             Berrange"
             <berrange at redhat.                                          To
             com>                      Barrow H Kwan
                                       <bhkwan at thoughtworks.com>
             11/22/2006 04:12                                           cc
             AM                        fedora-xen at redhat.com
                                                                   Subject
                                       Re: [Fedora-xen] Can't allocate
             Please respond to         memory (12)
                "Daniel P.
                 Berrange"
             <berrange at redhat.
                   com>

On Tue, Nov 21, 2006 at 11:40:57PM -0800, Barrow H Kwan wrote:
>
> This happen when I tried to create a Windows Guest.  After few days of
> struggling, I just found out Domain-0 has been assigned 99% of the
physical
> memory "BY DEFAUT".   I am wondering
>
> 1. Why does Fedora assign 99% to all phsical memory to Domain-0 ?

Dom0 gets essentially 100% of all memory at boot time. XenD will use the
balloon driver to take memory away from Dom0 when it is needed to launch
a new guest. Of course this relies on you not actively using that memory
in Dom0 but in general it just works. If balooning were failing though
you would see a different error - one saying it was unable to balloon
down the dom0. The 'cannot allocate memory' error suggests a more
fundamental problem.

> 2. Why does this memory allocation error happen with the Windows Guest?

Running 'xm dmesg' shortly after creating the guest may be helpful
in tracking down actual errors.

Regards,
Dan.
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