One critical config factor should be the loop speed (I like using my cpu, please tell your demo to leave it alone). Have a look at how processing.js handles its FPS.

I made some modifications on the code. It doesn't relate to processing.js, but at least the cpu usage is decreased. What I've tried is not processing the Loop function when the nodes inside the canvas don't move anymore (in steady position). The position of nodes and lines are also not updated until one node is dragged.

I attached the updated js-mindmap.js with comments inside