Slick2D StateBasedGame taking 20% cpu?

I’ve been using Slick2D for over a year now and decided to dive into StateBasedGame. Oddly enough, even after setting the maximum update interval and framerate, it still takes up 20% of my GPU.

Image of the issue:
Here’s all the code:

Seriously I don’t see what’s wrong. It can’t be my PC as my CPU is an Intel i7 3770 and my GPU is a GTX 660. I also have 8gb of ram so it can’t be memory issues…
To make things short, is there anything I can do about it? Is it an error in slick2d’s end of the code or am I doing something wrong? Any help is strongly appreciated.
Thank you for your time,

Turns out it’s vsync causing the trouble. It never used to do that (or at least I don’t remember that happening). What do you suggest… Leave it or keep it?

Some drivers implement vsync with a busy loop.

Use this class I wrote, which is used as the implementation of LWJGL’s Display.sync(freq)

while(...) {
   // render

   // throttle framerate

It trades a tiny bit of accuracy for the lowest possible CPU consumption.