When using Windows VMs on my MacBook Retina, often they’d start using excessive CPU after I switched back to my OS X screen.
This is very distracting, for instance during presentations, as it also starts humming the fans at close to 100 Hz (for non techies: nearly 6000 rpm).
When switching back to the VM, and going to Task Manager soon enough, I observed a MsMpEng+high+cpu+usage.
Since I knew this was caused by Windows Defender, I first tried to “Excluded files and locations” MsMpEng.exe, but that did not help.
My second thought was that it was caused by idle behaviour. Disabling that was indeed the cause. Since doing that was kind of hard to circumvent, here is how:
