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![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000];](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-27-2048.jpg)
![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a)](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-28-2048.jpg)
![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a)](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-29-2048.jpg)
![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-30-2048.jpg)
![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100 x100](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-31-2048.jpg)
![Mind the gap byte[][][] b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100 x100 x250](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-32-2048.jpg)
![header 4 1 3 2 6 =24bx64C IBM J9 Java7 for ebay Structure: header 8 =16bx64C byte[8]: *Could be as little as 4 bytes (JavaOne 2011)](https://image.slidesharecdn.com/javamemorypresentationibm-140401173022-phpapp02/75/Java-memory-presentation-IBM-7-33-2048.jpg)
Uploaded byYury Bubnov
Java memory presentation IBM 7
The document discusses Java memory and garbage collection. It begins by demonstrating how allocating objects can lead to OutOfMemoryErrors. It then covers topics like object layout, heap size, memory addressing, and different garbage collection algorithms between Java implementations. Balanced garbage collection and avoiding PermGen issues are also summarized.
Java memory presentation IBM 7
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- 2. Object o =new Object();
- 3. Object o =new Object(); java.lang.OutOfMemoryError: Java heap space
- 4. Object o =new Object(); java.lang.OutOfMemoryError: Java heap space
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- 8. class Structure{ byteb; short i; Object o; }
- 9. 1 2 4/8 classStructure{ byte b; short i; Object o; }
- 10. class Structure{ byteb; short i; Object o; } mark klass 2 1 1 4
- 11. class Structure{ byteb; short i; Object o; } 2 8 mark klass 2 1 1 4
- 12. class Structure{ byteb; short i; Object o; } mark klass 2 1 5 8
- 13. class Structure{ byteb; short i; Object o; } mark klass 2 1 5 8 4 8
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- 17. Memory address ...01100100100111011001011000 32 bitpointer .... to 35 bit
- 18. Memory address ...01100100100111011001011000 32 bitpointer .... to 35 bit 2^35≈32GB (25-28GB Heap)
- 19. Memory address ...01100100100111011001011000 32 bitpointer .... to 35 bit 2^35≈32GB (25-28GB Heap) IBM J9: Java 6 SR1, by default since Java7 SR4 Hotspot: since Java 6u14, by default since u23
- 20. class Structure{ byteb; short i; Object o; } mark klass 1 2 1 4 4
- 21. class Structure{ byteb; short i; Object o; } 3 8 mark klass 1 2 1 4 4
- 22. klass flags monitor 4 13 2 2 =24b klass flags size* monitor 8 1 3 2 2 klass flags monitor 1 3 4 2 2 =40b =24b i386 x64 x64C IBM J9 Java6
- 23. What’s the objectsize? class Structure{ byte b; short i; Object o;}
- 24. What’s the objectsize? HS 32b 16b HS 64b before u14 32b HS 64b after u14 (u27) 24b J9 32b 24b J9 64b 40b J9 64b compressed 24b class Structure{ byte b; short i; Object o;}
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- 26. Mind the gap byte[][][]b = new byte[10][100][1000];
- 27. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000];
- 28. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a)
- 29. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a)
- 30. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100
- 31. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100 x100
- 32. Mind the gap byte[][][]b = new byte[1000][100][10]; byte[][][] b = new byte[10][100][1000]; 4.832.024= 1.000.000+ 808.000(r)+2.020.020(h)+1.004.004(a) 1.032.344= 1.000.000+ 8.080(r)+20.220(h)+4.044(a) x100 x100 x250
- 33. header 4 1 3 26 =24bx64C IBM J9 Java7 for ebay Structure: header 8 =16bx64C byte[8]: *Could be as little as 4 bytes (JavaOne 2011)
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- 35. Garbage Collection 1. Startsif allocation fails or System.gc()* called or condition met
- 36. Garbage Collection 1. Startsif allocation fails or System.gc()* called or condition met 2. Stop-of-the-world operation
- 37. Garbage Collection 1. Startsif allocation fails or System.gc()* called or condition met 2. Stop-of-the-world operation 3. Mark, Sweep and Compact*
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- 43. A B 0 00 C D E 0 0 0 0 0 0 0 0 0 0 Mark A B C DE
- 44. 1 A B 0 0 CD E 0 0 0 0 0 0 0 0 0 0 A Mark A B C DE
- 45. 1 A B 0 C DE 0 0 0 0 0 0 0 0 0 Mark A B C DE B C 1 1
- 46. 1 A B 0 C DE 0 0 0 0 0 0 0 0 Mark A B C DE CE 1 1 1
- 47. 1 A B 0 C DE 0 0 0 0 0 0 0 0 Mark A B C DE E 1 1 1
- 48. 1 A B 0 C DE 0 0 0 0 0 0 0 0 Mark A B C DE 1 1 1
- 49. 1 A B CD E 0 0 0 Mark A B C DE 1 1 11 1 1 1 1 1
- 50. 1 A B CD E 0 0 0 Mark A B C DE 1 1 11 1 1 1 1 1
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- 52. References 1. Strong -always marked ! 2. Soft - not marked if too old or need memory ! 3. Weak - not marked if no strong reference ! 4. Phantom - correct implementation of finalize() method
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- 65. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 66. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 67. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 68. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 69. Sweep ... 1 00 1 1 1 0 0 0 1 1 ... Serial
- 70. Sweep ... 1 00 1 1 1 0 0 0 1 1 ... ... 1 0 0 1 1 1 0 0 0 1 1 ... ... 1 0 0 1 1 1 0 0 0 1 1 ...
- 71. Sweep ... 1 00 1 1 1 0 0 0 1 1 ... ... 1 0 0 1 1 1 0 0 0 1 1 ... ... 1 0 0 1 1 1 0 0 0 1 1 ...
- 72. Sweep ... 1 00 1 1 1 0 0 0 1 1 ... Parallel ... 1 0 0 1 1 1 0 0 0 1 1 ... ... 1 0 0 1 1 1 0 0 0 1 1 ...
- 73. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 74. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 75. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 76. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 77. Sweep ... 1 00 1 1 1 0 0 0 1 1 ...
- 78. Sweep ... 1 00 1 1 1 0 0 0 1 1 ... Concurrent
- 79. 1 1 00 1 1 1 0 0 0 1 1 ... Compact 1 1 1 1 1 1 1 0 0 0 0 0 ...
- 80. optthuput (default inJava6) parallel mark and compact. contiguous heap ! optavgpause concurrent mark and sweep. contiguous heap ! gencon (default in Java7) copying GC for young area concurrent mark for old area ! balanced (new for Java7) heap split to small regions (G1) Types of Garbage Collection
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- 92. Balanced GC 0 FreeFree 1 3 Free 0 0 2 0 Free 2 10 11 5 0 2 Free 3 1 1 Free 15 Free 0
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- 94. Balanced GC 1. Partialgarbage collection (PGC)
- 95. Balanced GC 1. Partialgarbage collection (PGC) 2. Global mark phase (GMP)
- 96. Balanced GC 1. Partialgarbage collection (PGC) 2. Global mark phase (GMP) 3. Global garbage collection (GGC)
- 97. Partial Garbage Collection 1.All Eden regions 2. Regions from CMP 3. Statistics
- 98. Partial Garbage Collection 0Free 0 1 3 2 Free 1 Free 2 4 Free 1. All Eden regions 2. Regions from CMP 3. Statistics
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- 131. Paging 1. Linux/Windows useVirtual memory and “paging” to reference physical ! 2. Pages mapped to physical only when referenced ! 3. OS manages pages
- 132. Real size ofJava Process?
- 133. Real size ofJava Process? 1. Architecture: 32 vs 64
- 134. Real size ofJava Process? 1. Architecture: 32 vs 64 2. JVM vendor: Oracle vs IBM
- 135. Real size ofJava Process? 1. Architecture: 32 vs 64 2. JVM vendor: Oracle vs IBM 3. JVM version incl. update
- 136. Real size ofJava Process? 1. Architecture: 32 vs 64 2. JVM vendor: Oracle vs IBM 3. JVM version incl. update 4. JVM settings
- 137. Real size ofJava Process? 1. Architecture: 32 vs 64 2. JVM vendor: Oracle vs IBM 3. JVM version incl. update 5. OS (above applies) 4. JVM settings
- 138. Real size ofJava Process? 1. Architecture: 32 vs 64 2. JVM vendor: Oracle vs IBM 3. JVM version incl. update 5. OS (above applies) + Run under real load for long time 4. JVM settings
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- 154. Heap (HS) X XXXX X
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- 158. Heap (HS) X XXXX X
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- 161. Garbage Collection Serial ParallelConcurrent Which one to choose?