I have an Ubuntu VM that's thrashing swap due to a small guest memory allocation on a host with lots of free ram. It appears the guest kernel is compiled to support hot-adding RAM, is there way to get virtualbox to mount more ram without shutting down the running VM?
I don't need zero downtime, I can do a state-save, but I don't want have to restart the multi-day processing job in progress on the guest.
Guest is Ubuntu 12.04, Host is OSX 10.7, both x64.
Best Answer
VirtualBox does not support adding more memory in this fashion. However, in many cases it will still be worth it to restart the computation, because the speed may increase by a factor of a hundred or more by using RAM as opposed to a hard drive.
An important note, even if your VM is "thrashing" that does not mean that the RAM is not getting used by windows (caching the disk that the VM is using) and thus the thrashing is having little/no impact.
In order to find out if this is the case, then just check the speed of the operation, and see if there is a change (or was a change) when the "thrashing started" or if the amount of RAM that is taken up by the VirtualBox process is significantly more than amount of RAM the guest has.