1. Workshop - November 2011 - Toulouse Verification of software properties: scheduling analysis and worst case execution time Jean BERTRAND, Jérémie POULY – CNES Axel BONESS, François BERTRAND – CEA LETI

2. Workshop - November 20112 Otawa Otawa computes Worst Case Execution Time (WCET) Uses Linear Programming (LP) methods to maximize cost function (processing time) Supports several CPU architectures PowerPc, M68HCS, ARM, LEON

3. Workshop - November 20113 OTAWA in our use case SWARM CPU implements numerous tasks Validation of our real-time application is therefore complex and painful The need for tools easing WCET computation is obvious OTAWA is not intrusive therefore can be used even late in the project

4. Workshop - November 20114 Otawa system footprint Disk usage : 280Mo Our configuration Portable Dell D630 Virtual machine 512Mo RAM / 5Go disk Ubuntu 9.10 May function anywhere Ligthweight

5. Workshop - November 20115 Speed Code size is irrelevant Branches are relevant It means: Computation intensive code is easy to analyse Decisional code is harder to analyse Nevertheless: Computing WCET on hundreds of branches is computationally immediate

6. Workshop - November 20116 GUI Well structured GUI

7. Workshop - November 20117 Assembler view

8. Workshop - November 20118 Cordic 32 bits analysis User specified Multiplierselection Architecturetuning

9. Workshop - November 20119 Limitations (branches) Tricky WCET Same functionnality Nevertheless WCET computed is a correct bound

10. Workshop - November 201110 Limitations (indirect call)

11. Workshop - November 201111 Limitations (impact) Indirect call present in: Function table IO managment Event managment C++ polymorphism Limited impact on actual real time software WCET computation Meaning of WCET including IO or event Consider C++ polymorphism in RT system !!!

12. Workshop - November 201112 Conclusion Tool is user friendly Free Easy usage GUI Lightweight Computed WCET are reliable OTAWA is non-intrusive Roadmap identifies technical breakthrough

13. Workshop - November 201113 Questions Please ask