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DMP: Deterministic Shared Memory Multiprocessing

ECE 259 / CPS 221 Advanced Computer Architecture II. DMP: Deterministic Shared Memory Multiprocessing. Joseph Devietti et al. Presenter : Tae Jun Ham 2012. 3. 19. Abstract. Most current shared memory multicore and multiprocessor systems are nondeterministic .

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DMP: Deterministic Shared Memory Multiprocessing

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  1. ECE 259 / CPS 221 Advanced Computer Architecture II DMP: Deterministic Shared Memory Multiprocessing Joseph Devietti et al. Presenter : Tae Jun Ham 2012. 3. 19

  2. Abstract • Most current shared memory multicore and multiprocessor systems are nondeterministic. • Non-determinism makes debugging and testing hard. • Previous approaches were based on replay • But replay is only useful for debugging • Based on deterministic inter-thread communication, this paper suggests several ways to achieve deterministic shared memory multiprocessing

  3. Determinism • What is Deterministic Parallel Execution? • Executes multiple threads that communicate via shared memory • Should produce the same output if given the same program input • What causes Non-determinism? • Software sources : concurrent threads, the state of memory pages, power saving mode, disk and I/O buffer, and some OS system calls. • Hardware sources : state of caches, predictor tables and bus priority controller, and bus arbiters. In other words, almost all microarchitectural structures.

  4. Non-determinism

  5. Non-determinism

  6. DMP-Serial (Fine-Grained)

  7. DMP-Serial (QBcount)

  8. DMP-Serial (Coarse-Grained)

  9. DMP-ShTab • Communication-Free Region: Parallel • Communication : Serial • Rules • Without token: Read for shared address Write for own address • With token: Can do everything

  10. DMP-ShTab

  11. DMP-ShTab

  12. DMP-TM & DMP-TM-Fwd

  13. DMP-TM & DMP-TM-Fwd

  14. DMP-TM & DMP-TM-Fwd

  15. QB-SyncFollow & QB-Sharing QB SyncFollow : After unlock, pass the token QB Sharing : After finishing works on shared data, pass the token

  16. Evaluation - Performance Serial : Linear slowdown with the increasing number of threads ShTab : 38% TM-Fwd : 21%

  17. Evaluation - Quanta size sensitivity In general, larger quanta is slower. Serial case is less sensitive to quanta size.

  18. Evaluation - Heuristics on quanta size Effective for ShTab. SyncFollow benefits for some workloads.

  19. Evaluation - Sw-DMP Author says : In summary, this data shows that Sw-DMP-ShTab does not unduly limit performance scalability for multithreaded applications.

  20. Discussions • Can this system deployed? • Too much performance overhead • Implementation Complexity • Which one do you prefer? DMP vs Deterministic replay • Possible power saving with DVFS?

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