Bug 378381

Summary: ballooning doesn't work properly
Product: [Fedora] Fedora Reporter: Thorsten Scherf <tscherf>
Component: xenAssignee: Xen Maintainance List <xen-maint>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: low Docs Contact:
Priority: low    
Version: 8   
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Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2007-11-12 13:06:38 EST Type: ---
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Description Thorsten Scherf 2007-11-12 12:58:09 EST
Description of problem:
setup: 2GB machine, 1 domU with mem-max of 500M and actual memory usage of 256M,
Dom0 uses 1.8G. When I allocate more memory to DomU using "xm mem-set vm1 400",
there is no error and even "xm list" shows 1800M for Dom0 and 400M for vm1 DomU.
running top inside the DomU only shows ~200M available memory, that's correct. 


Version-Release number of selected component (if applicable):
xen-3.1.0-13.fc8
kernel-xen-2.6.21-2950.fc8




How reproducible:
run xm mem-set to assign more memory to a DomU than available to the system

Steps to Reproduce:
1.see above
2.
3.
  
Actual results:
no error


Expected results:
error that there is no more memory available and that you have to shrink the
memory allocation for dom0 in order to assign more memory to a domU.

Additional info:
Comment 1 Daniel Berrange 2007-11-12 13:06:38 EST
The 'mem-set' command merely sets a *target value* for a guest, it does not
attempt to immediately allocate it. The balloon driver in the guest will try to
allocate memory from the hypervisor to meet this target - if there's not enough
available, it will retry (pretty much forever) until it can get enough. In your
case all your memory is assigned to Dom0 so there's nothing for the HV to give
to DomU. You need to lower the allocation for Dom0 manually. This is explicitly
not done automatically.