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

2. 2 In the Beginning…

3. 3 There was the Core.

4. 4 And it was Good.

5. 5 It gave us our Daily Speed.

6. 6 Until the Apocalypse.

7. 7 And the Speed was no Moore.

8. 8 And then came a False Prophet…

9. 9

10. 10 Want speed?

11. 11 I BRING YOU THE GIFT OF PARALLELISM!

12. 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…

13. 13

14. 14

15. 15

16. 16

17. 17

18. 18 pthreads race conditions atomicity violations deadlock order violations

19. 19 Salvation?

20. 20

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

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

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

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

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

26. 26 Isolation shared address space disjoint address spaces

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

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

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

30. 30 “Shared Memory”

31. 31 Snapshot pages before modifications “Shared Memory”

32. 32 Write back diffs “Shared Memory”

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

34. 34 D THREADS performance analysis

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

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

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

38. 38 Dthreads detailed analysis D THREADS : Detailed Analysis

39. 39 Dthreads detailed analysis D THREADS : Detailed Analysis

40. 40 Dthreads detailed analysis D THREADS : Detailed Analysis

41. 41 Scalability D THREADS : Scalable Determinism

42. 42 Scalability D THREADS : Scalable Determinism

43. 43 Scalability D THREADS : Scalable Determinism

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

45. 45 End

46. 46 Scheduler Determinism

47. 47 Excluding Outliers D THREADS : Without Outliers Just 5% slower than pthreads

48. 48 Commit Protocol Time Twin Page Diff Global State Local State

49. 49 a0b0a1b1 D THREADS Example Execution a0 b0a0b0a0b0 if(a == 0) b = 1; if(b == 0) a = 1; Global State Committed State a1 b1

50. 50 No Problem a0b0 if(a == 0) b = 1; if(b == 0) a = 1; a1b1

51. 51 That’s Better. a0b0 lock(); if(a == 0) b = 1; unlock(); lock(); if(b == 0) a = 1; unlock(); b1

52. 52 a0b0a1 lock(); if(a == 0) b = 1; unlock(); lock(); if(b == 0) a = 1; unlock(); Or is it?

53. 53 Determinism Is this enough?

54. 54 Robust Determinism

55. 55 External Nondeterminism socket = open_socket(80); listen(socket);

56. 56 Problem already solved http://www.gnu.org/s/pth/

57. 57 Overhead

58. 58 Wrap-Up Determinism Robust Determinism Internal Determinism

59. 59 Wrap-Up Threads to Processes Commit Before Synch. Commit In Token Order

60. 60 Overhead with CoreDet 7.8 [ASPLOS 10] Performance: D THREADS & CoreDet vs. pthreads

61. 61 How D THREADS Provides Determinism Isolation Deterministic Time Deterministic Order

62. 62 Evaluation Phoenix http://mapreduce.stanford.edu http://parsec.cs.princeton.edu