A Framework for the Derivation of WCET Analyses for Multi-Core - PowerPoint PPT Presentation

A Framework for the Derivation of WCET Analyses for Multi-Core Processors t i f A r a c t C o m p * t * l e n t e * e * t s S i W n s A T e o l R C l E D C * o e c * E s u u m e e E R n * o t e t v y s a E * d d a l e t a u Michael Jacobs, Sebastian Hahn, Sebastian Hack Department of Computer Science Saarland University July 7, 2016 saarland university computer science

saarland university Context of Our Work computer science Timing verification ◮ Worst-case execution time (WCET) analysis ◮ Scheduling theory / response time analysis Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 1 / 31

saarland university Context of Our Work computer science Timing verification ◮ Worst-case execution time (WCET) analysis ◮ Scheduling theory / response time analysis Multi-core processors ◮ Shared resources: buses, caches, . . . ◮ Shared-resource interference ⋆ Strong impact on performance ◮ Must be considered in timing verification Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 1 / 31

saarland university Context of Our Work computer science Timing verification ◮ Worst-case execution time (WCET) analysis ◮ Scheduling theory / response time analysis Multi-core processors ◮ Shared resources: buses, caches, . . . ◮ Shared-resource interference ⋆ Strong impact on performance ◮ Must be considered in timing verification Scope of our work ◮ WCET analysis for multi-core processors ◮ Static analysis ◮ Non-probabilistic ◮ Not (yet) integrated with response time analysis Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 1 / 31

saarland university computer science Motivation Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 2 / 31

saarland university Existing Work computer science WCET Analysis and Response Time Analysis for Multi-Core Processors [Kelter and Marwedel, 2014] [Chattopadhyay et al., 2012] [Schranzhofer et al., 2010] [Schliecker et al., 2009] [Schliecker and Ernst, 2010] [Pellizzoni et al., 2010] [Schranzhofer et al., 2011] [Dasari et al., 2011] [Giannopoulou et al., 2012] [Liang et al., 2012] [Dasari and Nélis, 2012] [Nowotsch, 2014] [Altmeyer et al., 2015] Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 3 / 31

saarland university Existing Work computer science WCET Analysis and Response Time Analysis for Multi-Core Processors [Kelter and Marwedel, 2014] } enumeration of all interleavings [Chattopadhyay et al., 2012] [Schranzhofer et al., 2010] [Schliecker et al., 2009] [Schliecker and Ernst, 2010] [Pellizzoni et al., 2010] [Schranzhofer et al., 2011] [Dasari et al., 2011] [Giannopoulou et al., 2012] [Liang et al., 2012] [Dasari and Nélis, 2012] [Nowotsch, 2014] [Altmeyer et al., 2015] Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 3 / 31

saarland university Existing Work computer science WCET Analysis and Response Time Analysis for Multi-Core Processors [Kelter and Marwedel, 2014] } enumeration of all interleavings � [Chattopadhyay et al., 2012] only support TDMA bus arbitration [Schranzhofer et al., 2010] [Schliecker et al., 2009] [Schliecker and Ernst, 2010] [Pellizzoni et al., 2010] [Schranzhofer et al., 2011] [Dasari et al., 2011] [Giannopoulou et al., 2012] [Liang et al., 2012] [Dasari and Nélis, 2012] [Nowotsch, 2014] [Altmeyer et al., 2015] Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 3 / 31

saarland university Existing Work computer science WCET Analysis and Response Time Analysis for Multi-Core Processors [Kelter and Marwedel, 2014] } enumeration of all interleavings � [Chattopadhyay et al., 2012]  only support TDMA bus arbitration [Schranzhofer et al., 2010]      [Schliecker et al., 2009]      [Schliecker and Ernst, 2010]      [Pellizzoni et al., 2010]      [Schranzhofer et al., 2011]  [Dasari et al., 2011] rely on compositionality    [Giannopoulou et al., 2012]      [Liang et al., 2012]      [Dasari and Nélis, 2012]     [Nowotsch, 2014]     [Altmeyer et al., 2015] Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 3 / 31

saarland university Motivating Example computer science All 6 Behaviors of a Simple Toy Program: = non-interfered execution Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 4 / 31

saarland university Motivating Example computer science All 6 Behaviors of a Simple Toy Program: = non-interfered execution = direct interference effect Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 4 / 31

saarland university Motivating Example computer science All 6 Behaviors of a Simple Toy Program: = non-interfered execution = direct interference effect = indirect interference effect ◮ only as consequence of direct interference Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 4 / 31

saarland university Classical Compositional Timing Analysis computer science For our Example: Typical compositional analysis Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 5 / 31

saarland university Classical Compositional Timing Analysis computer science For our Example: Typical compositional analysis = 10 time units Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 5 / 31

saarland university Classical Compositional Timing Analysis computer science For our Example: Typical compositional analysis = 10 time units Unsoundness Underestimates WCET Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 5 / 31

saarland university Increasing Penalty in Compositional Analysis computer science For our Example: Compositional analysis Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 6 / 31

saarland university Increasing Penalty in Compositional Analysis computer science For our Example: Compositional analysis Add indirect effects to penalty = 15 time units Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 6 / 31

saarland university Increasing Penalty in Compositional Analysis computer science For our Example: Compositional analysis Add indirect effects to penalty = 15 time units Limitations Imprecision Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 6 / 31

saarland university Increasing Penalty in Compositional Analysis computer science For our Example: Compositional analysis Add indirect effects to penalty = 15 time units Limitations Imprecision How to bound indirect effects per direct effect for a HW? Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 6 / 31

saarland university Increasing Penalty in Compositional Analysis computer science For our Example: Compositional analysis Add indirect effects to penalty = 15 time units Limitations Imprecision How to bound indirect effects per direct effect for a HW? Not possible for HW with domino effects! Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 6 / 31

saarland university A Novel Analysis by Us computer science "WCET Analysis for Multi-Core Processors with Shared Buses and Event-Driven Bus Arbitration" at RTNS 2015 [Jacobs et al., 2015] not compositional ◮ explicitly models interference in core pipeline Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 7 / 31

saarland university A Novel Analysis by Us computer science "WCET Analysis for Multi-Core Processors with Shared Buses and Event-Driven Bus Arbitration" at RTNS 2015 [Jacobs et al., 2015] not compositional ◮ explicitly models interference in core pipeline sound & precise scalable ◮ octa-core processors ◮ out-of-order execution Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 7 / 31

saarland university Focus of This Talk computer science Concepts ◮ used during derivation of [Jacobs et al., 2015] Our Paper embeds concepts in formal framework rigorous soundness proofs Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 8 / 31

saarland university computer science The Derivation of a WCET Analysis Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 9 / 31

saarland university Concrete-System Behavior computer science Set Traces of system behaviors Traces Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 10 / 31

saarland university The Actual WCET computer science Maximum execution time over all system behaviors execution time WCET Traces BCET 0 Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 11 / 31

saarland university Approximation of System Behavior computer science Set � Traces of abstract traces A ˆ t ∈ � Traces describes ( γ trace ): ◮ system behaviors and/or ◮ spurious behaviors � ˆ Traces ∈ t γ trace Traces Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 12 / 31

saarland university Soundness of an Approximation computer science � Traces must overapproximate all system behaviors � Traces γ trace Traces Michael Jacobs WCET Analyses for Multi-Core Processors July 7, 2016 13 / 31