Composable Resource Sharing Based on Latency-Rate Servers

Verification of application requirements is becoming a bottleneck in system-on-chip design, as the number of applications grows. Traditionally, the verification complexity increases exponentially with the number of applications and must be repeated if an application is added, removed, or modified. Predictable systems offering lower bounds on performance have been proposed to manage the increasing verification complexity, although this approach is only applicable to a restricted set of applications and systems. Composable systems, on the other hand, completely isolate applications in both the value and time domains, allowing them to be independently verified. However, existing approaches to composable system design are either restricted to applications that can be statically scheduled, or share resources using time-division multiplexing, which cannot efficiently satisfy tight latency requirements. In this paper, we present an approach to composable resource sharing based on latency-rate servers that supports any arbiter belonging to the class, providing a larger solution space for a given set of requirements. The approach can be combined with formal performance analysis using a variety of well-known modeling frame works. We furthermore propose an architecture for a resource front end that implements our concepts and provides composable service for any resource with bounded service time. The architecture supports both systems with buffers dimensioned to prevent overflow and systems with smaller buffers, where overflow is prevented with flow control. Finally, we experimentally demonstrate the usefulness of our approach with a simple use case sharing an SRAM memory.