Maybe we can turn this thread into sharing disturbing RMW experiences, mine was porting a small node from noetic to humble and seeing a 20x higher CPU hit.
Turns out lots of small high frequency messages (aka 90% of what’s typically sent through ROS) are a worst case scenario for all existing DDSes. A match made in hell.
It’s even worse for the hobbyist/academic space, I’m at the point where I’m no longer using ROS for small side projects that don’t require any of the large stacks, but roll MQTT instead since it gets the job done efficiently, reliably and with zero platform related headaches.