[malandrew]

On that note are there any changes or improvements on the horizon that would let you fast user switch between two or more booted and running operating systems. It'd be great in the future if you could allocate a small chunk of your RAM to keeping the background machine in a chunk of RSm so it switches faster than you can switch between users on the same OS. E.g. Of 16GB of RAM, 12GBis allocated to the foreground OS and 4GB to the background. Then when you switch you get a near instantaneous switch and the 8GB difference is allocated to the now current foreground system as necessary.

[kilburn]

This can be done today using kvm's memory ballooning. Essentially, you install a driver in the guest VM and it takes care of (1) reclaiming RAM from the guest OS when the host OS needs more; and (2) providing more RAM to the guest if needed and available.