JVM heap (IV)

JVM（ Four ）

Pile up

Here we mainly record the understanding of heap

Heap memory partition

• The new generation
  • Eden
  • From Survivor
  • To Survivor
• Old age

The new generation

form
It mainly stores new objects , The proportion in heap memory is 1/3
It's divided into three areas Eden、From Survivor、To Survivor

Eden
Eden The new generation of 8/10, Every time the garbage is recycled ,Eden All objects in the zone will be cleaned up

Survivor
Survivor In the Cenozoic, the area is the largest 1/10, Every garbage collection From Survivor Will be cleaned up ,To Survivor Will receive surviving objects

Old age

In the old days, it mainly stored memory objects with long life cycle in applications .

Method area

change
stay jdk1.6 And before , The method area is implemented by the permanent generation
jdk1.7, Put the string constant pool into heap memory
stay jdk1.8 after , The method area is implemented by a meta space

Runtime constant pool
Store values referenced by symbols

jdk1.6 Pile up 、 Method area