Providing message delivery guarantees in pipelined flit-buffered multiprocessor networks

Abstract

Real-time applications when mapped to distributed memory multiprocessors produce periodic messages with an associated deadline and priority. Real-time extensions to wormhole routing (WR) with multiple virtual channels (VCs), suffer from unbounded priority inversion, rendering the global priority order ineffective. We propose a new flow control mechanism called Preemptive Pipelined Circuit Switching for Real-Time messages (PPCS-RT). To bound the priority inversion, we extend the model to PPCS-RTph, with preemption history stack for each VC. For the PPCS-RTph model, we describe a simple feasibility test and validate the test through flit level simulations. To improve the percentage of feasible messages, and average link utilization of the feasible message set, we also evaluate an enhanced PPCS-RTph model with additional architectural features.