Credit Borrow and Repay: Sharing DRAM with minimum latency and bandwidth guarantees

Multi-port memory controllers (MPMC) play an important role in system-on-chips by coordinating accesses from different subsystems to shared DRAMs. The main challenge of MPMC design is optimize quality-of-service by simultaneously satisfying different-and often competing-requirements, including bandwidth and latency. While previous works have attempted to address the challenge, the proposed solutions are heuristic and often cannot provide bandwidth and/or latency guarantees. In this paper, we propose a new technique called Credit-Borrow-and-Repay (CBR) that augments a dynamic scheduling algorithm drawn from the networking community, improving it to achieve minimum latency while preserving minimum bandwidth guarantees. Our experiments show that on typical multimedia workloads, the cache response latency can be improved as much as 2.5X.