并发编程之Java 对象头的详细解析

1. |--------------------------------------------------------------|
2. |                    Object Header (64 bits)                   |
3. |------------------------------------|-------------------------|
4. |       Mark Word (32 bits)          |   Klass Word (32 bits)  |
5. |------------------------------------|-------------------------|

1. |---------------------------------------------------------------------------------|
2. |                             Object Header (96 bits)                             |
3. |--------------------------------|-----------------------|------------------------|
4. |        Mark Word(32bits)       |   Klass Word(32bits)  |  array length(32bits)  |
5. |--------------------------------|-----------------------|------------------------|

1. |-------------------------------------------------------|--------------------|
2. |                  Mark Word (32 bits)                  |        State       |
3. |-------------------------------------------------------|--------------------|
4. |    hashcode:25  | age:4 |   biased_lock:0   |   01    |       Normal       |
5. |-------------------------------------------------------|--------------------|
6. |thread:23|epoch:2| age:4 |   biased_lock:1   |   01    |       Biased       |
7. |-------------------------------------------------------|--------------------|
8. |          ptr_to_lock_record:30              |   00    | Lightweight Locked |
9. |-------------------------------------------------------|--------------------|
10. |          ptr_to_heavyweight_monitor:30      |   10    | Heavyweight Locked |
11. |-------------------------------------------------------|--------------------|
12. |                                             |   11    |    Marked for GC   |
13. |-------------------------------------------------------|--------------------|

1. |--------------------------------------------------------------------|--------------------|
2. |                          Mark Word (64 bits)                       |        State       |
3. |--------------------------------------------------------------------|--------------------|
4. | unused:25 | hashcode:31 | unused:1 | age:4 | biased_lock:0 |  01   |        Normal      |
5. |--------------------------------------------------------------------|--------------------|
6. | thread:54 |   epoch:2   | unused:1 | age:4 | biased_lock:1 |  01   |        Biased      |
7. |--------------------------------------------------------------------|--------------------|
8. |                    ptr_to_lock_record:62                   |  00   | Lightweight Locked |
9. |--------------------------------------------------------------------|--------------------|
10. |                 ptr_to_heavyweight_monitor:62              |  10   | Heavyweight Locked |
11. |--------------------------------------------------------------------|--------------------|
12. |                                                            |  11   |    Marked for GC   |
13. |--------------------------------------------------------------------|--------------------|