Exploiting the capabilities of communications co-processors

Communications coprocessors (CCPs) have become commonplace in modern massively parallel processors (MPPs) and networks of workstations. These coprocessors provide dedicated hardware support for fast communication. In this paper, we study how to exploit the capabilities of CCPs for executing user-level message handlers. We show, in the context of active messages and Split-C, that we can move message handling code to the coprocessor, thus freeing the main processor for computational work. We address the important issues that arise, such as synchronization, and the limited computational power and flexibility of CCPs. We have implemented coprocessor versions of both active messages and Split-C. These implementations, developed on the Meiko CS-2, provide us with an excellent experimental platform to evaluate the benefits of a communications coprocessor architecture.