Same problem with with Docker for Mac 1.12.0-rc4-beta20 (build: 10404).
I have a shared volume defined in docker-compose for live reloading code for development. When starting the container com.docker.hyperkit is running at 259% and com.docker.osxfx is running at 140% +.
My containers are a MeanJs code base and Mongo container. The shared volume in docker-compose is:
volumes:
- .:/home/mean:rw