@pichlo: Warning "Unable to find libthread_db matching inferior's thread library, thread debugging will not be available" suggests that we cannot look into other threads. Any tips on how to get rid of it are welcome. There is https://stackoverflow.com/a/14368545, not sure if its relevant.

Re heavy lifting: in this respect, finding route is easy. It probably takes more CPU to process where you are relative to the route. I'd have to look into how to optimize that part (in future).