Engineering Cross-Layer Fault Tolerance in Many-Core Systems

Engineering Cross-Layer Fault Tolerance in Many-Core Systems

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  Engineering Cross-Layer Fault-Tolerance in Many-CoreSystems PhD Student: Rem Gensh Supervisor: Professor Alexander Romanovsky Thesis Committee: Professor Alex Yakovlev, Dr Alexei Iliasov
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  Definitions • Fault toleranceis a means for achieving dependability, allowing us to prevent the system failure in the presence of faults. • Layer. Abstraction layer, system component. • Cross-layer approach (or design) is used when it is more efficient to distribute the task between several layers rather than execute it only at one layer. • Many-core systems are those containing tens, hundreds or thousands cores (multi-core systems have 2-8 cores) 2
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  Introduction • Systems’ complexityand abstraction • TCP/IP as a motivating example • Many core systems • Layered fault tolerance • Cross-layer fault tolerance 3
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  Systems’ Complexity andAbstraction • Abstraction simplifies the understanding of the system structure • Layers of the computer system • OSI model • TCP/IP (Internet protocol suite) • Object-oriented programming • Components of the system are considered as black boxes • Each component should provide predefined service according to its interface 4
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  TCP/IP as amotivating example 5
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  TCP/IP cross-layer faulttolerance • All layers participate in error detection and error recovery • Error detection and recovery is performed by cooperative activities of several layers • If an error is not detected at the lower layer it will be detected and recovered at the higher layer • Efficiency and flexibility of TCP/IP 6 Layer Error detection Error recovery Application Status codes Retransmission or custom recovery Transport CRC-16 TCP: ack., neg. ack., ARQ, seq. number Internet CRC-16 Discard corrupted packet Link CRC-32 Discard corrupted packet
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  Many-core systems • 10,100 or even 1000 cores • Heterogeneous architectures • Redundant cores for ensuring fault tolerance • Performance, energy efficiency and reliability are very important factors for many-core systems 7
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  Layered fault tolerance •Faults can occur at the different layers of the system stack • Major part of errors is handled at the layer, where they are detected. • Convenience for developer • Predominance of convenience over the system efficiency 8
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  Layered fault tolerance •System layers are considered separately • Unnecessary error corrections are possible • Above layer can not specify the required quality of service of the layer that is below • Not optimal in terms of performance and energy consumption 9
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  Cross-Layer Fault Tolerance •Fault tolerance will be distributed across the system stack • Useful information about the system state will be shared among the layers • Various application domains • Above layers will have the possibility to specify current needs and required service level 10
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  Cross-layer design forwireless sensor networks • Single layer approach cannot share important information among different layers • Each layer does not have complete information. Optimal operation of the entire network cannot be guaranteed • Single layer approach does not have the ability to adapt to the environmental change L. Carnevali, L. Ridi, E. Vicario, "Stochastic Fault Trees for cross-layer power management of WSN monitoring systems," IEEE Conference on Emerging Technologies & Factory Automation, pp. 1-8, 2009. P. Rachelin Sujae, M. Vigneshpandi, "A Cross Layer Fault Tolerant Communication Architecture for Wireless Sensor Networks," Middle-East Journal of Scientific Research, pp. 1292- 1296, 2014. Y. Wang, H. Wu, F. Lin, N.F. Tzeng, "Cross-Layer Protocol Design and Optimization for Delay/Fault-Tolerant Mobile Sensor Networks (DFT-MSN’s)," IEEE Journal on selected areas in communications, vol. 26, no. 5, pp. 809-819, 2008. 11
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  Challenges • Investigate thetrade-off between reliability, performance and energy-consumption in many-core systems • Ensure cross-layer fault tolerance for many-core systems • Demonstrate that applying the cross-layer fault tolerance can improve performance and energy-efficiency 12
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  Plan • Implement acase-study to gain an experience in developing cross-layer fault tolerance • Apply Order Graphs to model cross-layer fault tolerance, power consumption and performance of many-core systems • Design novel mechanisms, libraries and patters that will help in engineering cross-layer fault tolerance of many-core systems 13
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  Case study: Carnumber plate recognition application • Several character recognition algorithms • Possibility to specify the operational mode: reliability, performance, energy efficiency or certain tradeoffs between these parameters. • Recover two types of errors: • CPU core error. • Insufficient Quality of Service. 14
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  Conclusion • Systems’ complexityand abstraction • Layered fault tolerance • Cross-layer fault tolerance 15