Contributions

1. A Cross-Layer, Error-Aware Methodology for Reliable Design of Resource Constrained Embedded Systems Knob Motivation • Mobile devices are resource-constrained (e.g., limited battery) • Reliability is a significant design concern (e.g., soft errors) • Cross-layer interactions and conflicts arise between system properties, e.g., performance, power, and reliability: • Voltage scaling increases soft error rate exponentially • Redundancy techniques increase overheads of power and performance PPC (an unprotected cache and a protected cache) (1)Reduce the exposed space space Cross-Layer Error-Aware Approaches PPC (Partially Protected Cache) CC-PROTECT (Cooperative Cross-layer Protection) Error-prone Networks (2)Reduce the vulnerable time Unprotected Cache • Soft error rate is increasing exponentially as technology scales • Redundancy-based techniques (e.g., Error Correction Codes) are effective but expensive in terms of power and performance • Propose a PPC architecture to provide an unequal data protection for maximal reliability with minimal overheads • Cooperative error-aware methods across abstraction layers Protected Cache How To Partition Data? • Our approach exploits error-tolerance and error control schemes across layers • Our approach coordinates and optimizes mobile embedded systems for maximal reliability with minimal overheads of power and performance Memory Mobile Video Application time • PPC– Unequal protection at hardware exploiting error-tolerance at application • CC-PROTECT – Middleware-driven cooperative exploitation of errors and error control schemes across layers Application (EAVE) Error Tolerance Error Rate CC-PROTECT Error Resilience Intentional or Soft-Error Induced Frame Drop Injection Rate Middleware/ Operating System Network Error-Aware Video Encoder (EAVE) frame drop Network frame loss Error- Aware Video Original Video Error-Controller (e.g., frame dropping) Error-Resilient Encoder (e.g., PBPAIR) Loss Rate Unequal Protection Error- Injected Video Defect Rate • Not all data is equally failure critical (2) Vulnerable time closely estimates failure rate Error Injection Rate & Frame Loss Rate Drop & Forward Recovery (DFR) PPC Hardware (PPC) Feedback • Failure non-critical data (e.g., multimedia data) • Failure critical data (e.g., program variables) • Pages causing high vulnerable time are failure critical data Monitor & Translate SER Trigger Selective DFR Support EAVE & PPC Parameter frame K frame K+1 Middleware/OS invulnerable Mobile Embedded System Incoming Eviction Read Write data Error detection Unprotected Cache Protected Cache EDC • Compiler and OS help to partition data into a PPC (Error Detection Codes) t0 t1 t2 t3 PPC Vulnerable Publications Contributions Future Directions [1] K. Lee, M. Kim, N. Dutt, and N. Venkatasubramanian. “Error exploiting video encoder to extend energy/qos tradeoffs for mobile embedded systems”. In 6th IFIP Working Conference on Distributed and Parallel Embedded Systems (DIPES), Sep. 2008 [2] K. Lee, A. Shrivastava, N. Dutt, and N. Venkatasubramanian. “Data partitioning techniques for partially protected caches to reduce soft error induced failures”. In 6th IFIP Working Conference on Distributed and Parallel Embedded Systems (DIPES), Sep. 2008 [3] K. Lee, A. Shrivastava, I. Issenin, N. Dutt, and N. Venkatasubramanian. “Mitigating soft error failures for multimedia applications by selective data protection”. In Int.Conference on Compilers, Architecture, & Synthesis for Embedded Systems (CASES), Oct. 2006. [4] S. Mohapatra, R. Cornea, H. Oh, K. Lee, M. Kim, N. Dutt, R. Gupta, A. Nicolau, S. Shukla, and N. Venkatasubramanian. “A cross-layer approach for power-performance optimization in distributed mobile systems”. In Next Generation Software Program in conjunction with IEEE International Parallel and Distributed Processing Symposium (IPDPS), April 2005. [5] K. Lee, A. Shrivastava, M. Kim, N. Dutt, and N. Venkatasubramanian. “Cross-layer interactions of error control schemes for mobile multimedia systems”. In Technical Report, University of California at Irvine, Apr. 2008. • Improve energy consumption and performance without losing reliability at the cost of QoS • Open opportunity to explore the expanded design space by exploiting error-awareness (error-tolerance and error-resilience) across system layers • Combine approaches across layers for further improvements • Develop middleware approaches to coordinate multiple system parameters across layers in distributed embedded systems • Cooperate approaches to maximize the reliability with minimal loss in terms of power, performance, and QoS Kyoungwoo Lee (kyoungwl@ics.uci.edu) Donald Bren School of Information and Computer Sciences, University of California at Irvine, CA 92697, USA Co-advisors: Nikil Dutt and Nalini Venkatasubramanian