LOFT: A High Performance Network-on-Chip Providing Quality-of-Service Support

Providing quality-of-service (QoS) for concurrent tasks in many-core architectures is becoming important, especially for real-time applications. QoS support for on-chip shared resources (such as shared cache, bus, and memory controllers)in chip-multiprocessors has been investigated in recent years. Unlike other shared resources, network-on-chip (NoC) does not typically have central arbitration of accesses to the shared resource. Instead, each router shares the responsibility of resource allocation. While such distributed nature benefits the scalable performance of NoC, it also dramatically complicates the problem of providing QoS support for individual flows. Existing approaches to address this problem suffer from various shortcomings such as low network utilization and weak QoS guarantees. In this work, we propose LOFT No architecture which features both high network utilization and strong QoS guarantees. LOFT is based on the combination of two mechanisms: a) locally-synchronized frames (LSF), which is a distributed frame-based scheduling mechanism that provides flexible QoS guarantees to different flows and b) flit-reservation (FRS), which is a flow-control mechanism integrated in LSF that improves network utilization. The experimental results show that LOFT delivers flexible and reliable QoS guarantees while sufficiently utilizes available network capacity to gain high overall throughput.