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Register a new userAnalysis of buffering effects on hard real-time priority-preemptive wormhole networks
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Added by
Leandro Indrusiak
Publication date
2016
fields
Informatics Engineering
and research's language is
English
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There are several approaches to analyse the worst-case response times of sporadic packets transmitted over priority-preemptive wormhole networks. In this paper, we provide an overview of the different approaches, discuss their strengths and weaknesses, and propose an approach that captures all effects considered by previous approaches while providing tight yet safe upper bounds for packet response times. We specifically address the problems created by buffering and backpressure in wormhole networks, which amplifies the problem of indirect interference in a way that has not been considered by the early analysis approaches. Didactic examples and large-scale experiments with synthetically generated packet flow sets provide evidence of the strength of the proposed approach.
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Simulations and runtime measurements are some of the methods which can be used to evaluate whether a given NoC-based platform can accommodate application workload and fulfil its timing requirements. Yet, these techniques are often time-consuming, and hence can evaluate only a limited set of scenarios. Therefore, these approaches are not suitable for safety-critical and hard real-time systems, where one of the fundamental requirements is to provide strong guarantees that all timing requirements will always be met, even in the worst-case conditions. For such systems the analytic-based real-time analysis is the only viable approach. In this paper the focus is on the real-time communication analysis for wormhole-switched priority-preemptive NoCs. First, we elaborate on the existing analysis and identify one source of pessimism. Then, we propose an extension to the analysis, which efficiently overcomes this limitation, and allows for a less pessimistic analysis. Finally, through a comprehensive experimental evaluation, we compare the newly proposed approach against the existing one, and also observe how the trends change with different traffic parameters.
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Inter-datacenter networks connect dozens of geographically dispersed datacenters and carry traffic flows with highly variable sizes and different classes. Adaptive flow routing can improve efficiency and performance by assigning paths to new flows according to network status and flow properties. A popular approach widely used for traffic engineering is based on current bandwidth utilization of links. We propose an alternative that reduces bandwidth usage by up to at least 50% and flow completion times by up to at least 40% across various scheduling policies and flow size distributions.
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