Dthreads: Efficient Deterministic Multithreading

1. Dthreads: Efficient Deterministic Multithreading Tongping Liu, Charlie Curtsinger, Emery Berger Insanity: Doing the same thing over and over again and expecting different results.

2. In the Beginning…

3. There was the Core.

4. And it was Good.

5. It gave us our Daily Speed.

6. Until the Apocalypse.

7. And the Speed was no Moore.

8. And then came a False Prophet…

10. Want speed?

11. I BRING YOU THE GIFT OF PARALLELISM!

12. color = ; row = 0; // globals void nextStripe(){ for (c = 0; c < Width; c++) drawBox (c,row,color); color = (color == )?  : ; row++; } for (n = 0; n < 9; n++) pthread_create(t[n], nextStripe); for (n = 0; n < 9; n++) pthread_join(t[n]); JUST USE THREADS…

18. race conditions atomicity violations pthreads deadlock order violations

19. Salvation?

21. Dthreads race conditions race conditions atomicity violations atomicity violations pthreads Dthreads deadlock deadlock order violations order violations deterministic

22. Dthreads Enables… Race-free Executions Replay Debugging w/o Logging Replicated State Machines

23. Overhead with CoreDet Dthreads: Efficient Determinism 7.8 Usually faster than the state of the art

24. Overhead with CoreDet Dthreads: Efficient Determinism 7.8 Generally as fast or faster than pthreads

25. Dthreads: Easy to Use % g++ myprog.cpp–l thread p

26. Isolation disjoint address spaces shared address space

27. Performance: Processes vs. Threads 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 threads processes Normalized Execution Time 1 2 4 8 16 32 64 128 256 512 1024 Thread Execution Time (ms)

28. Performance: Processes vs. Threads 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 threads processes Normalized Execution Time 1 2 4 8 16 32 64 128 256 512 1024 Thread Execution Time (ms)

29. Performance: Processes vs. Threads 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 threads processes Normalized Execution Time 1 2 4 8 16 32 64 128 256 512 1024 Thread Execution Time (ms)

30. “Shared Memory”

31. “Shared Memory” Snapshot pagesbeforemodifications

32. “Shared Memory” Write back diffs

33. Update in Deterministic Time & Order Parallel Serial Parallel mutex_lock “Thread” 1 cond_wait “Thread” 2 pthread_create “Thread” 3

34. Dthreadsperformance analysis

35. The Culprit: False Sharing Core 2 Core 1 Thread 1 Thread 2 Invalidate Main Memory

36. The Culprit: False Sharing Core 2 Core 1 Thread 1 Thread 2 Invalidate 20x Main Memory

37. Dthreads: Eliminates False Sharing! Core 2 Core 1 Process 1 Process 2 Process 1 Process 2 Global State

38. Dthreads detailed analysis Dthreads: Detailed Analysis

39. Dthreads detailed analysis Dthreads: Detailed Analysis

40. Dthreads detailed analysis Dthreads: Detailed Analysis

41. Scalability Dthreads: Scalable Determinism

42. Scalability Dthreads: Scalable Determinism

43. Scalability Dthreads: Scalable Determinism

44. Dthreads Dthreads % g++ myprog.cpp–l thread p

45. End