Inter-process communication (IPC) is one of the core functions of modern robotics middleware. We propose an efficient IPC technique called TZC (Towards Zero-Copy). As a core component of TZC, we design a novel algorithm called partial serialization. Our formulation can generate messages that can be divided into two parts. During message transmission, one part is transmitted through a socket and the other part uses shared memory. The part within shared memory is never copied or serialized during its lifetime. We have integrated TZC with ROS and ROS2 and find that TZC can be easily combined with current open-source platforms. By using TZC, the overhead of IPC remains constant when the message size grows. In particular, when the message size is 4MB (less than the size of a full HD image), TZC can reduce the overhead of ROS IPC from tens of milliseconds to hundreds of microseconds and can reduce the overhead of ROS2 IPC from hundreds of milliseconds to less than 1 millisecond. We also demonstrate the benefits of TZC by integrating it with TurtleBot2 to be used in autonomous driving scenarios. We show that by using TZC, the braking distance can be 16% shorter than with ROS.

Shared memory provides the fastest form of inter-process communication. Sharing polymorphic objects between different address spaces requires solving the issue of sharing pointers. In this paper, we propose a method, named Indexed Virtual Tables (IVT for short), to share polymorphic objects efficiently. On object construction, the virtual table pointers are replaced with indexes, which are used to find the actual virtual table pointers on dynamic dispatch. Only a few addition and load instructions are needed for both operations. Experimental results show that the IVT can outperform prior techniques on both object construction time and dynamic dispatch time. We also apply the proposed IVT technique to several practical scenarios, resulting the improvement of overall performance.