Red Hat Bugzilla – Bug 219727
[RHEL5] Libvirt support for automatically ballooning down dom0 when ballooning up a domU
Last modified: 2008-06-23 17:06:53 EDT
+++ This bug was initially created as a clone of Bug #219724 +++ Description of problem: Now that domain ballooning works from a kernel/hypervisor perspective, it would be nice if the tools were a little more accomodating for users. In particular, if you start a domain with the following in the config file: maxmem = "512" memory = "300" you can balloon up the domU, but *only* if you first balloon down dom0 sufficiently. You can successfully accomplish the balloon by running: xm mem-set Domain-0 1024 (or whatever, freeing up enough memory from dom0) xm mem-set domU 500 It would be nice if you could just use the virt-manager "Memory" screen to increase the amount of memory to a domU, which would automatically balloon down dom0 and balloon up domU. I believe this requires some support from libvirt, which is why I filed the bug against it; if it's really just a problem with virt-manager, feel free to move to the right component.
I think those APIs are present in libvirt, basically virDomainSetMemory() http://libvirt.org/html/libvirt-libvirt.html#virDomainSetMemory Dynamically change the target amount of physical memory allocated to a domain. If domain is NULL, then this change the amount of memory reserved to Domain0 i.e. the domain where the application runs. This function may requires priviledged access to the hypervisor. W.r.t. the suggestion of using this in virt-manager, I think balooning works when creating a new domain automatically, but I'm not sure what is done when one resize it dynamically, so reassigning to virt-manager for confirmation. Daniel
This works in virt-manager and has for a while. Closing as CURRENTRELEASE