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• dalvik GC @akachochin

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@akachochin

3. MFPnetbsdOS 4. 5. 6. 7. GC

()

8. Web Page2.3GC 9. OS 10. GCGC 11. 1 - GC

12. 13. GC 14. 2 - GC

GC(Ex.malloc())(free())

15. free()free()free() 16. 17. Dalvik

DalvikAndoroidGC

18. 19. (Copy GC) 20. 21. 1 --

22. ( ) 23. 1 --

()

24. 2 -

25. Java gDvm 26. GC?

27. GC 28. grep -ri concurrent * 29. 30. vm/alloc/HeapSource.c:dvmCollectGarbageInternal(false, GC_CONCURRENT); 31. GC?

static void *gcDaemonThread()

32. 33. dvmCollectGarbageInternal() 34.

dvmCollectGarbageInternal

()

35. () 36. vm/alloc/Heap.hGcReason GC_CONCURRENT 37. GC GC_CONCURRENT 38.

dvmCollectGarbageInternal

GC_CONCURRENT

39. 1.GC 40. 2.GC VM ( ) (dvmResumeAllThreads(SUSPEND_FOR_GC);) 41. -> GC VM GC 42.

dvmCollectGarbageInternal

13 2 VM

43. GC 44. GC GC 45.

dvmCollectGarbageInternal (dvmMalloc())

46. GC 47. GC 48. dvmMalloc()

dvmMalloc()

49. VMJavanewVMdvmAllocObject()dvmMalloc() 50. dvmMalloc()

dvmMalloc() -> tryMalloc() ->dvmHeapSourceAlloc()

51. 52. mspace_calloc() 53. countAllocation() ->dvmHeapBitmapSetObjectBit() 54. mspace_calloc() 55. mspace_calloc() 56. dvmHeapBitmapSetObjectBit()

liveBits

57. GCVM 58. GC GcHeap HeapSource MarkContext GcMarkContext GC HeapSource liveBits markBits liveBits MarkContext bitmap stack finger 2 59. bitmap (liveBits,MarkBits) 8byte 8byte liveBits MarkBits 8byte 60. dvmHeapBitmapSetObjectBit()

8bytelivebit

61. 24byteliveBits 1 liveBits 1 62. dvmHeapBitmapSetObjectBit()

Javanew()

63. bit(bit) 64. liveBits 65.

dvmCollectGarbageInternal ( 1)

dvmCollectGarbageInternalGC

66. 1.(suspend) 67. 2.root 68. 3.card(card) 69. 4.(resume) 70. 5. 71.

dvmCollectGarbageInternal ( 2)

6.(suspend) 7. 8. 9. 10.(resume)

72.

dvmCollectGarbageInternal ( )

73. 1.(1 4) 74. 2.(5-6) 75. 3.(7-8) 76. 4.(9) 77.

dvmCollectGarbageInternal ( )

dvmHeapMarkRootSet()

78. JavanewdvmGcScanRootClassLoader() 79. gDvm 80.

dvmCollectGarbageInternal ( )

markClassObject()dvmMarkObjectNonNull - markObjectNonNull setAndReturnMarkBit()markbitobjobjmarkbit(1)

1 MarkBits 1 81.

dvmCollectGarbageInternal ( )

dvmCollectGarbageInternal() dvmClearCardTable() CardTable 0

1. cardTable 128byte

82. 2. cardTable Darty 83.

dvmCollectGarbageInternal ( )

cardtable livebit

cardTable liveBits Darty livebit16( 128byte) CardTable 84.

dvmCollectGarbageInternal ( )

dvmHeapScanMarkedObjects()

85. 2 86. 1.dvmHeapBitmapScanWalk() 87. -> markBits()() 88. 2.processMarkStack() 89. -> () 90. () 91.

dvmCollectGarbageInternal ( )

dvmHeapBitmapScanWalk()

92. markBit 1 markBits LiveBit 1 93.

dvmCollectGarbageInternal ( )

Java

Java 94.

dvmCollectGarbageInternal ( )

(finger) markBits 1

1 markBits finger markBits 1 95.

dvmCollectGarbageInternal ( )

finger markbit 1 stack

markBits finger markBits 1 96.

dvmCollectGarbageInternal ( )

StackmarkBit

97. 1.stack 98. 2.1markBits 99. 3.2 100. 13stack 101.

dvmCollectGarbageInternal ( )

stack 1 markBits 102.

dvmCollectGarbageInternal ( )

3136

103. 104.

dvmCollectGarbageInternal ( )

dvmHeapReMarkRootSet()

105. 2728 106.

dvmCollectGarbageInternal ( )

dvmHeapReScanMarkedObjects()

107. 108. dvmHeapReScanMarkedObjects() 109.

dvmCollectGarbageInternal ( )

2930cardTable

128bytecardTableDarty

A B C B B C 110.

dvmCollectGarbageInternal ( )

cardTable markbits 111.

dvmCollectGarbageInternal ( )

markbit

112.

dvmCollectGarbageInternal ( )

113. dvmHeapSweepUnmarkedObjects() 114. dvmHeapBitmapSweepWalk() 115.

dvmCollectGarbageInternal ( )

markbits livebits 1 GC 1 116.

dvmCollectGarbageInternal ( )

117. live & ~mark live ~mark & 0 0 0 0 1 0 1 0 0 1 1 1 118.

dvmCollectGarbageInternal ( )

461(DECODE_BITS)

119. (FLUSH_POINTERBUFsweepBitmapCallback 120. 121.

DalvikGCMark & Sweep

122. GC 123. 2Mark 124. sweep 125. 126.