DSP goes to 100% when connecting audio or midi from Ardour through a Carla plugin back into Ardour
See images for a better understanding
When patching from Ardour through a plugin of any kind in Carla and audio back through Ardour again DSP moves to 100%.
As you can also see from the last picture, as long as the midi / audio signal does not come from ardour tracks before going back into ardour, there is no problem.
Pictures alt: https://imgur.com/a/utRxNV4