What does the RTAS CPU usage monitor include?

[DC-Choppah]

I was wondering if the RTAS CPU monitor includes anything other than pro-tools RTAS?

The reason is, while working on a project, I suddenly got a warning message from Pro-tools about being low on CPU. I then started getting distortion from all my virtual instruments in the project. I checked the CPU usage and it showed RTAS CPU bouncing around at 38% or so. That was strange because it always sat at around 10-14% before, and I hadn't changed anything other than working on the music itself.

A little while little after I re-opened the project the RTAS CPU was back around 13% and no distortion.

So I was wondering if some other program or service was gobbling up CPU for a while and that this showed up in the RTAS CPU monitor.

Just wondering if there is something else I need to disable from running while I'm using Pro Tools.