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Total: 1
Onur Derin,
Emanuele Cannella,
and Todor Stefanov,
"HiPEAC Collaboration Grant Report".
HiPEACinfo newsletter no. 27,
July
2011
.
| Abstract | Thanks to the HiPEAC collaboration grant that I received in winter 2010, I worked with Emanuele Cannella and Todor Stefanov at LIACS, University of Leiden on the implementation of a task-aware middleware for fault-tolerant and adaptive KPN applications on an FPGA-based NoC platform. This is a summary of my collaboration. The complexity of multiprocessor systems on chip (MPSoCs) is rapidly increasing, driven by the technology improvement and the adoption of more and more complex applications in consumer electronics. Programming such complex systems at a low level of abstraction is extremely difficult and error-prone. A promising way to raise the level of abstraction is using models of computation (MoCs) to specify applications. Among these MoC, Kahn Process Networks (KPNs) have been widely studied and used for streaming/multimedia applications. A favorable feature of the KPN MoC is that its simple operational semantics allows for the easy adoption of system adaptivity mechanisms such as run-time resource management. System adaptivity is becoming increasingly important in the MPSoC domain for several reasons, such as dynamic variation of quality of service requirements, fault tolerance, or power efficiency. Networks-on-Chip (NoCs) are emerging communication infrastructures for MPSoCs that, among many other advantages, allow for system adaptivity. However, there is a mismatch between the generic structure of the NoCs and the semantics of the KPN MoC. Therefore, we investigated and proposed several approaches to overcome this mismatch. All of the proposed approaches consider system adaptivity as a driving objective and do not require specific hardware support from the platform. We proposed and implemented three middleware approaches, namely virtual connector, virtual connector with variable rate, and request-based, to execute Kahn Process Networks on Network-on-Chip architectures. The key differences between these approaches are the rate of acknowledgement of empty slots in the remote queues and the buffering requirement in the sender side. Experimental results on two applications (Sobel and MJPEG encoder) with very different computation and communication characteristics showed that the virtual connector approach outperforms the others in terms of the overhead in the total execution time when implementing communication-dominant applications. However, especially for this kind of applications, the price we pay for system adaptivity and generality is large in terms of performance, if compared to customized point-to-point systems. On the contrary, when the computation/communication ratio of an application is higher, as in the second case study, the overhead introduced by the execution on NoC with all the proposed middlewares is much lower. The overhead in terms of the amount of data transferred in the network is the least for request-based approach for both applications. |
| Keywords | kahn process networks (KPN), middleware, networks-on-chip (NoC), self-adaptivity |
| Research area | Fault tolerance |
| Document |  permanent link
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 is rapidly increasing, driven by the technology improvement and the adoption of more and more complex applications in consumer electronics. Programming such complex systems at a low level of abstraction is extremely difficult and error-prone. A promising way to raise the level of abstraction is using models of computation (MoCs) to specify applications. Among these MoC, Kahn Process Networks (KPNs) have been widely studied and used for streaming/multimedia applications. A favorable feature of the KPN MoC is that its simple operational semantics allows for the easy adoption of system adaptivity mechanisms such as run-time resource management. System adaptivity is becoming increasingly important in the MPSoC domain for several reasons, such as dynamic variation of quality of service requirements, fault tolerance, or power efficiency. Networks-on-Chip (NoCs) are emerging communication infrastructures for MPSoCs that, among many other advantages, allow for system adaptivity. However, there is a mismatch between the generic structure of the NoCs and the semantics of the KPN MoC. Therefore, we investigated and proposed several approaches to overcome this mismatch. All of the proposed approaches consider system adaptivity as a driving objective and do not require specific hardware support from the platform. We proposed and implemented three middleware approaches, namely virtual connector, virtual connector with variable rate, and request-based, to execute Kahn Process Networks on Network-on-Chip architectures. The key differences between these approaches are the rate of acknowledgement of empty slots in the remote queues and the buffering requirement in the sender side. Experimental results on two applications (Sobel and MJPEG encoder) with very different computation and communication characteristics showed that the virtual connector approach outperforms the others in terms of the overhead in the total execution time when implementing communication-dominant applications. However, especially for this kind of applications, the price we pay for system adaptivity and generality is large in terms of performance, if compared to customized point-to-point systems. On the contrary, when the computation/communication ratio of an application is higher, as in the second case study, the overhead introduced by the execution on NoC with all the proposed middlewares is much lower. The overhead in terms of the amount of data transferred in the network is the least for request-based approach for both applications.&p[images][0]=http://people.alari.ch/derino/apps/bebop/img/bebop-logo_w100.png "Facebook"){kind=logo}
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