Contention in shared caches caused by concurrently executing applications can lead to overall performance degradation in multiprocessor systems-on-chip (MPSoCs). To address this issue, various shared cache arbitration techniques have been proposed to manage cache bandwidth contention. These techniques focus on enhancing overall system performance; however, this optimization often comes at the expense of system fairness, leading to some applications experiencing disproportionate slowdowns, or, in the worst case, starvation. Therefore, an effective shared cache bandwidth management policy is needed to optimize performance while ensuring fairness across applications. We propose FARRE , a novel fairness aware request-response arbitration technique for shared caches. FARRE is designed to optimize performance while attempting to maintain a user-defined fairness threshold. We evaluate its effectiveness through extensive simulations including comparisons against state-of-the-art arbitration schemes. The results show that FARRE is able to maintain or exceed the input fairness thresholds, and improves system performance over standard fair scheduling policies such as round-robin; the performance improvement is 14% for lower fairness thresholds such as 0.5, and could even gain 5% performance for aggressive thresholds such as 0.9. Additionally, compared to the best performance optimization techniques, FARRE achieves 81% higher fairness.

Modern multi-processor systems-on-chip (MPSoCs) are characterized by caches shared by multiple cores. These shared caches receive requests issued by the processor cores. Requests that are subject to cache misses may result in the generation of responses . These responses are received from the lower level of the memory hierarchy and written to the cache. The outstanding requests and responses contend for the shared cache bandwidth. To mitigate the impact of the cache bandwidth contention on the overall system performance, an efficient request and response arbitration policy is needed. Research on shared cache management has neglected the additional cache contention caused by responses, which are written to the cache. We propose CABARRE , a novel request and response arbitration policy at shared caches, so as to improve the overall system performance. CABARRE shows a performance improvement of 23% on average across a set of SPEC workloads compared to straightforward adaptations of state-of-the-art solutions.

Ensuring the functional correctness of networks-on-chip (NoCs) can be particularly challenging, and communication-centric debug methodologies have been widely used by engineers to validate NoC functionality during post-silicon validation. Design-for-debug structures, such as trace buffers and monitors, are usually inserted in such systems-on-chip to enhance signal visibility. However, this debug hardware becomes underutilized once the chip goes into production. While the size and organization of the router buffers directly impact network throughput, these buffers also dominate the on-chip router area. We propose a scheme augmented virtual channel (AugVC) to reuse trace buffers to augment router buffers, with the objective of improving the overall network performance. The experimental results for a 64-node mesh network show that our proposed approach can reduce latency by up to 38.25% for transpose traffic compared to a baseline design with reduced buffer sizes. We also propose an extension, output port directed virtual channel (ODVC), that uses a modified virtual channel assignment strategy, on the basis of the designated output port of a network packet. This strategy reduces the average packet latency and area of the router by 45% and 32.4%, respectively.

Runtime verification employs dedicated hardware or software monitors to check whether program properties hold at runtime. However, these monitors often incur high area and performance overheads depending on whether they are implemented in hardware or software. In this work, we propose DHOOM, an architectural framework for runtime monitoring of program assertions, which exploits the combination of a reconfigurable fabric present alongside a processor core with the vestigial on-chip Design-for-Debug hardware. This combination of hardware features allows DHOOM to minimize the overall performance overhead of runtime verification, even when subject to a given area constraint. We present an algorithm for dynamically selecting an effective subset of assertion monitors that can be accommodated in the available programmable fabric, while instrumenting the remaining assertions in software. We show that our proposed strategy, while respecting area constraints, reduces the performance overhead of runtime verification by up to 32% when compared with a baseline of software-only monitors.

With the increasing complexity of modern Systems-on-Chip, the possibility of functional errors escaping design verification is growing. Post-silicon validation targets the discovery of these errors in early hardware prototypes. Due to limited visibility and observability, dedicated design-for-debug (DFD) hardware such as trace buffers are inserted to aid post-silicon validation. In spite of its benefit, such hardware incurs area overheads, which impose size limitations. However, the overhead could be overcome if the area dedicated to DFD could be reused in-field. In this work, we present a novel method for reusing an existing trace buffer as a victim cache of a processor to enhance performance. The trace buffer storage space is reused for the victim cache, with a small additional controller logic. Experimental results on several benchmarks and trace buffer sizes show that the proposed approach can enhance the average performance by up to 8.3% over a baseline architecture. We also propose a strategy for dynamic power management of the structure, to enable saving energy with negligible impact on performance.