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Managed Runtime Systems: Lecture 04 - Memory Management (Continued)

zakkak
February 21, 2018

Managed Runtime Systems: Lecture 04 - Memory Management (Continued)

zakkak

February 21, 2018
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  1. Managed Runtime Systems Lecture 04: Memory Management (Continued) Foivos Zakkak

    https://foivos.zakkak.net Except where otherwise noted, this presentation is licensed under the Creative Commons Attribution 4.0 International License. Third party marks and brands are the property of their respective holders.
  2. Acknowledgments The following slides are based on the corresponding slides

    of Mario Walczko about Memory Management: Memory management part 1 Memory management part 2 Memory management debugging hints Managed Runtime Systems 1 of 13 https://foivos.zakkak.net
  3. The Tri-color Abstraction Color each object depending on its current

    state Initially all objects are white (non processed) Each time an object gets traced it gets colored gray After an object has been scanned it gets colored black Managed Runtime Systems 2 of 13 https://foivos.zakkak.net
  4. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  5. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  6. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  7. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  8. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  9. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  10. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  11. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  12. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  13. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  14. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  15. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  16. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  17. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  18. Tri-Color Tracing roots A B C D E F G

    H A H F A D G H F E D E G Managed Runtime Systems 3 of 13 https://foivos.zakkak.net
  19. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  20. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  21. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  22. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  23. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  24. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  25. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  26. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  27. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  28. Copying Tri-color roots From To To From A B C

    D C B D C B D Managed Runtime Systems 4 of 13 https://foivos.zakkak.net
  29. Main Advantage of the Tri-Color Abstraction Allows for incremental garbage

    collections Reduce the length of stop-the-world pauses Mutator threads and GC-scanning threads can run concurrently More on incremental and concurrent GCs on future lectures! Managed Runtime Systems 5 of 13 https://foivos.zakkak.net
  30. Main Drawback of Semi-space Collectors They require twice the memory!!!

    Managed Runtime Systems 6 of 13 https://foivos.zakkak.net
  31. Main Drawback of Semi-space Collectors They require twice the memory!!!

    and They copy long-lived data all the time!!! Managed Runtime Systems 6 of 13 https://foivos.zakkak.net
  32. The Generatinal Hypothesis Most objects die young! What if we

    could collect young objects separately? Managed Runtime Systems 7 of 13 https://foivos.zakkak.net
  33. Generational Collectors Further slice the heap in generations (usually eden,

    young, and old) Move surviving objects to older generation (called tenuring) Occasionally perform a full mark-and-sweep collection Managed Runtime Systems 8 of 13 https://foivos.zakkak.net
  34. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  35. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  36. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  37. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  38. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  39. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  40. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  41. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  42. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  43. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  44. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  45. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  46. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  47. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  48. Generational Collectors Eden Young Old A B C D E

    F G H D F I J K L M D K D K L Managed Runtime Systems 9 of 13 https://foivos.zakkak.net
  49. Keeping Track of Old to Young References Avoid scanning old

    generation at young collections Keep a set of old-to-young references (called remembered set) Monitor writes to reference fields of old objects (called write-barrier) Managed Runtime Systems 10 of 13 https://foivos.zakkak.net
  50. Card Marking write-barriers Keep a bit per memory block of

    old generation The bit indicates whether objects in the block reference young objects The card gets reset in every collection Managed Runtime Systems 11 of 13 https://foivos.zakkak.net
  51. Generational Collection in Action 2 4 6 8 10 12

    14 16 18 20 Perm Gen Old Gen New Gen Code Others VM Fig. 4: javac D- & E-cache contents, and heap usage 0 2 4 6 8 10 12 14 16 18 20 22 0 0.1 0.2 0.3 0.4 Cache 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 Cycles (billions) Heap Usage (MB) Fig. 7 Table 1 Fig. 8 E Figure Source: Introspection of a Java Virtual Machine under Simulation, Wright et al, Sun Labs TR-2006-159 Managed Runtime Systems 12 of 13 https://foivos.zakkak.net
  52. Tuning Generational Garbage Collectors Tenuring threshold Allocating directly to old

    space Size of generations Old space collectors Managed Runtime Systems 13 of 13 https://foivos.zakkak.net