Jetpack3.3 OpenCV functions acceleration on GPU


I’ve installed Jetpack3.3 on a host pc and a jetson.
This installation includes OpenCV 3.3.
There is something I don’t fully understand- I want OpenCV to run as much functions as it can on the GPU. Does that occur automatically? Should I do something in order to make it run on the GPU?
I’m talking about native OpenCV functions like image manipulation, opticalFlow, and other CV functions.
I’m aware of numba which can add headers to custom functions to run on the GPU, but I’m talking more about the native OpenCV functions which I don’t understand how to accelerate.

I’m using Python.

If someone can advise it would be great! I’m reading a lot of threads here and still didn’t catch this point and how to solve it.