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javajvmjava-17

In Java 17 what is the difference between the section Class and Metaspace in the output of jcmd VM.native_memory

The output of jcmd <pid> VM.native_memory shows a Class and Metaspace section like below

Class (reserved=1053604KB, committed=39012KB)
    (classes #46737)
    (  instance classes #44474, array classes #2263)
    (malloc=5028KB #107972) (peak=5042KB #107808) 
    (mmap: reserved=1048576KB, committed=33984KB) 
    (  Metadata:   )
    (    reserved=262144KB, committed=257280KB)
    (    used=255927KB)
    (    waste=1353KB =0.53%)
    (  Class space:)
    (    reserved=1048576KB, committed=33984KB)
    (    used=32654KB)
    (    waste=1330KB =3.91%)

and

 Metaspace (reserved=263756KB, committed=258892KB)
    (malloc=1612KB #1525) (at peak) 
    (mmap: reserved=262144KB, committed=257280KB)

Can someone tell me the difference between the Class and Metaspace sections? Is the Metadata shown under Class the same as Metaspace?

Output of java -version

openjdk version "17.0.11" 2024-04-16
OpenJDK Runtime Environment Temurin-17.0.11+9 (build 17.0.11+9)
OpenJDK 64-Bit Server VM Temurin-17.0.11+9 (build 17.0.11+9, mixed mode, sharing)
Solution

  • As pointed out by @apangin in the comment, from the question Class (reserved=1053604KB refers to Compressed Class Space, and Metaspace (reserved=263756KB refers to non-class space. For more explanation, read this answer by @apangin.