l i a b l eh kC o m p u t i n gL a b o r a t o r y Performance Yield-Driven Task Allocation and Scheduling for MPSoCs under Process Variation Presenter: Lin Huang Lin Huang and Qiang Xu CUhk REliable computing laboratory (CURE) The Chinese University of Hong Kong

Process Variation Becomes A Serious Concern The ever-increasing transistor variability Spatial correlation characteristic

Task Allocation and Scheduling for MPSoCs Given Determine Process variation affects performance yield Task Graph Task Schedule P1P1 P2P2 MPSoC

Limitations of Previous Work Only a few explicitly consider process variation All assume the task execution time follows Gaussian distribution In reality, it can be approximated with Gaussian distribution in some instances at best [Sarangi-ieeetsm08]

Limitations of Previous Work All assume the execution times of multiple tasks are s-independent This assumption ignores the spatial correlation characteristic of process variation

Limitations of Previous Work All assume the execution times of multiple tasks are s-independent This assumption ignores the spatial correlation characteristic of process variation Consider a pair of MPSoCs i, j

Limitations of Previous Work With correlation, statistical properties of s-independent Gaussian distribution are not applicable

Agenda Introduction and motivation Problem formulation Proposed quasi-static task allocation and scheduling algorithm Simulated annealing-based initial task scheduling Clustering-based performance yield enhancement Experimental results Conclusion

Initial Task Scheduling Modified simulated annealing technique Solution representation (scheduling order sequence; resource binding sequence) Example: ( τ 1, τ 3, τ 2, τ 4, τ 5 ; P 1, P 2, P 1, P 1, P 2 ) Performance yield estimation Closed-form statistical analysis is extremely difficult

Initial Task Scheduling Performance yield estimation Closed-form statistical analysis is extremely difficult Monte Carlo simulation schedule i.i.d. samples of MPSoC frequency map meet constraint (1) or not (0)

Initial Task Scheduling Efficiency of Monte Carlo simulation N – number of test chips M – number of chips meeting performance constraints N = 1,000, confidence level = 95% max = min = 0

Performance Yield Enhancement With the initial task schedule, some chips might cannot meet performance constraints Residual test chips Covered by initial schedule

Performance Yield Enhancement Iteratively generate additional task schedules k-mean clustering and objectively task schedule generation Three clusters

Performance Yield Enhancement Selection criteria generation Multilayer perceptron One time effort Training sample – test chips Inputs: frequency map Outputs: meet constraint or not Sigmoid function

Task Schedule Selection Given an MPSoC product Frequency map becomes available Forward propagation through selection criteria network Schedule selection rule … …

Experimental Setup Task graphs are generated by TGFF Task number: 31 – 152 Hypothetical MPSoCs Heterogeneous or homogeneous Core number: 4 – 8 Process variation model Multivariate normal distribution with spatial correlation [Sarangi- ieeetsm08] The distance pass which the correlation becomes zero = {0.1, 0.5} The variation = 3.2%

Experimental Results

S init 36.9% 59.3% 40.8%

Experimental Results

Conclusion We propose a novel quasi-static variation-aware task allocation and scheduling technique for MPSoC designs Initial task scheduling Simulated annealing Monte Carlo simulation Performance yield enhancement k-mean clustering Multilayer perceptron Experimental results demonstrate the effectiveness

Performance Yield-Driven Task Allocation and Scheduling for MPSoCs under Process Variation Thank you for your attention !