Java 8: From Permanent generation (PermGen) to Meta Space (metaspace)

Noun concept:

Meta-space: Metaspace
1, most of the class metadata is allocated in local memory.

2, by default, the class metadata is limited only by the available local memory (the capacity depends on the available virtual memory size of the 32/64-bit operating system).

3, the new parameter (maxmetaspacesize) is used to limit the size of local memory allocated to the class metadata. If this parameter is not specified, the meta-space is dynamically adjusted as needed at run time.

4, garbage collection for zombie classes and ClassLoader will take place when the metadata is used to reach the set value of the "maxmetaspacesize" parameter.

5, timely monitoring and adjustment of the meta-space is necessary to reduce the frequency of garbage collection and reduce delay. Persistent meta-space garbage collection instructions may exist for classes, memory leaks caused by class loaders, or inappropriate size settings.

Permanent generation: PermGen
1, this part of the memory space will be removed.
2, the parameters of the JVM:permsize and maxpermsize are ignored and a warning is given (if both parameters are set when enabled).

Meta-space Features:
1, each loader has dedicated storage space.
2, a class is not recycled separately.
3, the position of the object in the meta-space is fixed.
4, if it is found that an loader is no longer in stock, the relevant space will be collected throughout.

Java 8: From Permanent generation (PermGen) to Meta Space (metaspace)