Red Hat Bugzilla – Bug 378381
ballooning doesn't work properly
Last modified: 2007-11-30 17:12:22 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):
run xm mem-set to assign more memory to a DomU than available to the system
Steps to Reproduce:
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.
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.