There's the rub though. When I disable all the sleep code, and just have VSync enabled, it caps to 60fps. But it does not run at 16.66666666ms per frame.
The image I posted a couple above shows how long each frame takes, and it is erratic. Sometimes the render takes 16ms, sometimes 16.7ms, sometimes 17ms.
This is to be expected (especially if Triple Buffering is enabled, which you could check in your driver settings).
Is it also expected to have the frame sometimes take 5ms and sometimes .3ms? I am checking now if triple buffering is enabled, but I do know that double is, as that is the SDL_SwapBuffers() command.
Edit: Yes triple buffering is enabled and I tried disabling Intel Speedstep, virtualization, and disabled triple buffering and VSync via ~/.drirc file all to no avail.