Provide a mechinism to set a guest OS's process priority to idle

[Rom Walton]

I work on the BOINC project (​http://boinc.berkeley.edu). We have begun working on our client-side and server-side code to integrate using VirtualBox to execute CPU bound applications within a Linux guest VM.

BOINC's overall approach to running applications is to run them as the idle process priority class of the host operating system.

Our testers have reported that they have noticed that VM's start with the normal priority class thereby the system sometimes gets a little sluggish when responding to user input.

We would like a way to start a VM guest so that it is running in the hosts idle process priority class.

[Frank Mehnert]

A similar feature is on our TODO list. We are indeed planning to make the priority of the VM execution thread configurable. Although applying the policy to be only scheduled if the host is idle would be probably a bit too dangerous as the guest might not be scheduled for a long time then. Using the usual scheduling policy should at least work on POSIX systems (Linux, Solaris hosts) as these hosts normally schedule a thread at least at certain amounts of time, even if its priority is set to a very low value. Windows hosts might behave differently.