What does java "VM thread" do?

Question

I use jstack to output the thread info. And there is a thread: "VM Thread" prio=10 tid=0x0878b400 nid=0x760a runnable

What is this thread used to do? It takes 50% CPU usage and most of CPU time

Answer 1

I think it is the Garbage Collection thread. It does Garbage Collection.

Answer 2

How do you know that this thread is taking 50% usage? Being runnable doesn't mean its consuming cpu.

AFAIK this is used for internal java operation, possibly involved in GC.

Which version of java are you using? I would check you have an up to date version of Java and see if this still happens.

I would suggest you memory profile your application to see how much objects you are creating and see if you can reduce your object count to reduce any GC work load.