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Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks

Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks. - Ramkumar Shankar. Reference.

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Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks

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  1. Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks -Ramkumar Shankar

  2. Reference • C.Steiger, H.Walder and M.Platzner, “Operating Systems for Reconfigurable Embedded Platforms:Online Scheduling of Real-Time Tasks” ,IEEE Transactions on computers vol 53, No.11, pp. 1393-1407 Nov. 2004 • Web link: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1336761

  3. Outline • Models and Limitations • Practical OS • Target Architecture • OS Modules • Scheduling Real-Time Tasks • Techniques for 1D and 2D model • Results, Conclusion and Future Scope

  4. Preliminaries • Hardware task  Digital circuit that has been preplaced and prerouted. • Functional characteristics transparent to the OS. • Structural characteristics visible to the OS. • Area and timing requirements

  5. 1D and 2D area model

  6. Limitations of the area model • Internal Fragmentation • External Fragmentation • Assumes Homogeneity of the RC Device. • OS takes up some of the special resources • Tasks not relocatable

  7. Target Architecture

  8. Partitioning of the RC device

  9. Operating system modules

  10. Operating System Modules on CPU • Task Scheduler • Resource Manager • Task Preparation Unit • Raw Task Repository • COMM Driver • C/R Driver

  11. Operating System Modules on RC Device • Task Controller • Memory Management Unit(MMU) • Device Drivers • OS Bridge

  12. Scheduling Real-Time Tasks • Factors affecting the scheduling: • arrival time, execution time, deadline • Width, height • Constraints for the scheduler • Scheduled tasks must not overlap in space and time • The tasks must meet the deadline

  13. 1D Horizon Technique • Execution list (E) • Maintains tasks (Ti), Finish time(fi) and placement(xi) • Reservation List (R) • Stores all tasks scheduled but not executing • Horizon List(H) • Stores the position and time step at which the units become available.

  14. 1D Horizon Technique example

  15. 1D Stuffing Technique • Maintains Execution and Reservation lists • Maintains a free space list.

  16. Placement Algorithms and related issues • Free space management • Merging free spaces in Horizon Technique. • Mimic future tasks for Stuffing Technique. • Strip Packing • Scheduling tasks for 2D mesh – very costly

  17. Evaluation

  18. Results

  19. Conclusion and Further Work • Design issues for RC Hardware operating system. • Scheduling techniques for 1D and 2D area models • Scheduling tasks for non-real time systems • Tasks with unknown execution times • Tasks without deadlines • Periodic tasks

  20. Questions

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