1. 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

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?