why does Virtualbox use 15-20% CPU when VM is paused?

Question

I run VirtualBox 3.1 on Ubuntu with a Win XP guest. I have noticed to my surprise that when I pause the VM (its screen grays out) VirtualBox continues using 15-20% of the host's CPU.

Is this normal behavior?

Is there a way to avoid it? (Without saving the state of the VM and exiting VirtualBox.)

Thanks for any insights!

~lara

Answer 1

In order to lessen VirtualBox CPU usage at all times, resort to this weird hack.

Create a new virtual machine and do not install an operating system to it. Tell VirtualBox it will run DOS and give it the absolute minimum resources. Do not install an O/S. Run it, let it error out on boot and minimize it.

While running your real O/S in a second VM, you will see your idle Virtualbox CPU utilization drop to 3-5%.

Idea from jed4czar: http://ubuntuforums.org/showthread.php?s=58e862a814e65eb96f8fe8389b615366&t=838073&page=2

EDIT: To answer your questions directly

why does Virtualbox use 15-20% CPU when VM is paused?

It is a bug. It is always using 15-20% more CPU than it needs to, when any one VM is up, unless the hack provided is used.

Is there a way to avoid it?

See hack above.

Answer 2

I experienced this VirtualBox issue on a 2-cpu P4 machine with 3gigs ram running CentOS 5.5 host.

I did not experience this issue on an i720 8cpu machine with 8 gigs running 64-bit Win7. I ran 3 VMWare virtual machines plus the VirtualBox, all with 2-gigs memory, and had no CPU issues whatsoever.

This suggests either running on a "smallish" machine or on a Linux host is the problem.

Your solution worked well, thanks.

I note that these earlier posts are a year old, and my VirtualBox is the most recent Version 4.0.4, so Oracle has not fixed this bug yet.