Thread Blocking is Evil
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This is the simple version of the orinial one addressed at Deview2011.
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Thread Blocking is Evil
- 1. Thread Blocking Is Evil Game Network Component Team Kim, J.H.
- 2. CONCURRENCY
- 3. Why is Thread Blocking a Concern?
- 4. “The Free Lunch is OVER.” Herb Sutter December 2004
- 7. Write Multithreaded Application
- 8. CONCURRENCY
- 10. Thread Blocking
- 11. Starvation Deadlock
- 12. Starvation
- 13. Task A Task B 1: Lock 1: Sleep 0 msec 2: Sleep 1msec 3: Unlock
- 14. 1000 Process time(ms) 995 Task B 990 Task A 985 1 2 3 4 5 6 7 8 9 # of Thread
- 15. Deadlock Hold & Wait
- 16. Thread A Thread B 1A: Lock 1B: Lock 2A: Request 2B: Send Response 3A: Wait for Response 3B: Unlock 4A: Do something with Response 5A: Unlock
- 17. Thread A Thread B 1A: Lock 1B: Lock 2A: Request 2B: Send Response 3A: Wait for Response 3B: Unlock 4A: Do something with Response 5A: Unlock
- 18. My Problem
- 19. Framework for Lobby-Room style Game
- 21. Easy to write code because it’s all contained inside one function.
- 22. ‘Enter Room’ RPC ‘Authentication’ RPC Game Client Room Lobby
- 23. Game Client Room Lobby Call ‘Enter Room’ RPC Call ‘Authentication’ RPC ‘Authentication ‘Enter Room’ RPC ‘ RPC function Function body body Return ‘Authentication’ RPC Return ‘Enter Room’ RPC
- 24. Game Client Room Lobby Call ‘Enter Room’ RPC Call ‘Authentication’ RPC ‘Enter Room’ ‘Authentication RPC function RPC ‘ body Function body Return ‘Authentication’ RPC Return ‘Enter Room’ RPC
- 25. Game Client Room Lobby Response Delay Call ‘Enter Room’ RPC Call ‘Authentication’ RPC From Lobby Server ‘Enter Room’ ‘Authentication RPC function RPC ‘ body Function body Return ‘Authentication’ RPC Return ‘Enter Room’ RPC
- 26. Game Client Room Lobby Response Delay Call ‘Enter Room’ RPC Call ‘Authentication’ RPC From Lobby Server ‘Enter Room’ ‘Authentication RPC function RPC ‘ body Function body Room Server Return ‘Enter Room’ RPC Return ‘Authentication’ RPC throughput Decline
- 27. What is the Axis of Evil?
- 28. Game Client Room Lobby Call ‘Enter Room’ RPC Call ‘Authentication’ RPC Thread Blocking Return ‘Authentication’ RPC Return ‘Enter Room’ RPC
- 29. Inherent Limitation of RPC
- 30. Easy to write code because it’s all contained inside one function.
- 31. Can not split code because it’s all contained inside one function.
- 32. RPC::Result* JoinRoom(…) { … RPC::Result answer = RPC::SyncCall(“VerifyLobbyUserToken”, …); …. return result; }
- 33. What We Want
- 34. RPC Function Body Non-Blocking
- 35. What is the Essence of Problems?
- 36. Request & Wait
- 37. Solution
- 41. Cons: Can’t Write Sequential Code Can’t Use Stack Variable Can’t Split Programming Construct …
- 42. Too Difficult!!
- 43. Coroutine
- 46. Stack & Local Variable
- 47. But
- 48. Non-preemptive
- 50. Who does provide Coroutine?
- 51. C# Erlang Haskell JavaScript(since 1.7) Lua Perl Python(since 2.5) Ruby …
- 52. What about C++?
- 54. On Your Own!
- 56. Asynchronous Programming + Coroutine
- 57. Non-Blocking & Writing Sequential Code
- 58. Solution for Starvation
- 59. Before Task A Task B 1: Lock 1: Sleep 0msec 2: Sleep 2msec 3: Unlock
- 60. After Task A Task B Thread A 1: Sleep 0msec 1: Create & Resume Coroutine 2: Request Lock 3: Yield Non-Blocking Thread A’ 4: Resume 5: Sleep 2msec 6: Yield Break 7: Unlock Sequential Code
- 61. Before 1000 Process time(ms) 995 Task B 990 Task A 985 1 2 3 4 5 6 7 8 9 # of Thread
- 62. After 1500 Process time(ms) 1000 Task B 500 Task A 0 1 2 3 4 5 6 7 8 9 # of Thread
- 63. Solution for Deadlock Hold & Wait
- 64. Before Thread A Thread B 1A: Lock 1B: Lock 2A: Request 2B: Send Response 3A: Wait for Response 3B: Unlock 4A: Do something with Response 5A: Unlock
- 65. After Thread A Thread B 1A: Lock 1B: Lock 2A: Create & Resume Coroutine 2B: Send Response 3A: Request 3B: Unlock 4A: Yield Non-Blocking 5A: Unlock Thread A’ (invoked by response) 6A’: Lock 7A’: Resume 8A’: Do something with response 9A’: Yield Break 10A’: Unlock Sequential Code
- 66. Solution for My Problem
- 67. Game Client Room Lobby Call ‘Enter Room’ RPC Call ‘Authentication’ RPC Thread Blocking Return ‘Authentication’ RPC Return ‘Enter Room’ RPC
- 68. Before Room Thread Lobby Service 1R: Call ‘Authentication’ RPC function 1L: Process the request 2R: Wait for the response 2L: Send back the response 3R: Process
- 69. After Room Thread Lobby Service 1R: Create & Resume Coroutine 1L: Process the request 2R: Request 2L: Send back the response 3R: Yield Non-Blocking Room Thread’ (invoked by response) 4R’: Resume 5R’: Process 6R’: Yield Break Sequential Code
- 70. Request & Wait Request & Yield
- 71. Non-Blocking & Writing Sequential Code
- 72. Coroutine (Fiber) User-mode Scheduling Kernel-mode Scheduling Thread CPU CPU CPU CPU
- 73. RPC Coroutine Execution Pool Thread Pool RPC Task Queue Network I/O Thread Pool
- 74. Network I/O RPC Task RPC Execution Coroutine Thread Queue Thread Pool Network Event task enqueue task dequeue acquire coroutine coroutine RPC start Execution yield return Network resume Event task resume enqueue task dequeue resume yield break release coroutine pooling
- 75. Network I/O RPC Task RPC Execution RPC Execution Coroutine Thread Queue Thread 1 Thread 2 Pool Network Event task enqueue task dequeue acquire coroutine coroutine RPC resume Execution yield return Network resume Event task resume enqueue task dequeue resume yield break release coroutine pooling
- 76. RPC::Result* JoinRoom(…) { … RPC::Result answer = RPC::SyncCall(“VerifyLobbyUserToken”, …); …. return result; }
- 77. RPC::Result* JoinRoom(…) { … RPC::Result answer = RPC::SyncCallYield(“VerifyLobbyUserToken”, …); …. return result; }
- 78. T Blocking P Yield S # of Thread
- 79. Wrap-up
- 80. “The free lunch is OVER.” Write Multithreaded Application CONCURRENCY
- 81. Thread Blocking is Evil Starvation Deadlock
- 82. Asynchronous Programming + Coroutine
- 83. Non-Blocking + Writing Sequential Code
- 84. Request & Wait Request & Yield
- 85. Inspired by Jeffrey Richter ‘Simplified APM With The AsyncEnumerator’