compiz cpu usage explodes when VirtualBox is started

Running Ubuntu 15.10 with VirtualBox 5.1.2 and a Win10 guest OS. When I start VirtualBox (just VB, not the guest OS) compiz cpu usage goes over 150% and stays there for several minutes. When running the Win10 guest it is typically 160% with short bursts below 40% but then back to over 150%.

It looks like compiz is defective. I understand compiz is part of Unity. Do I need to switch desktops to get rid of compiz, or is there a fix for it?

Thanks.