JVM Memory Structure

JVM Memory Structure

I recently looked at some cases of Java Memory leakage and discussed it with several old buddies. I found that there are still many details that I didn't know before in the JVM. I will analyze them a little here. Let's take a look at the JVM internal structure --

The JVM memory structure mainly includes two subsystems and two components. The two subsystems are the classloader subsystem and the executionengine subsystem. The two components are the runtimedataarea component and the nativeinterface component.

Function of the classloader subsystem:

Load the content of the class file to methodarea in runtimedataarea Based on the given fully qualified name class name (such as Java. Lang. object ). Java programmers can use the extendsjava. Lang. classloader class to write their own classloader.

Role of the executionengine subsystem:

Execute the commands in classes. The core of any jvmspecification implementation (JDK) is executionengine. Different JDK, such as Sun's JDK and IBM's JDK, depend mainly on their respective executionengine.

Nativeinterface component:

Interaction with nativelibraries is an interface for interaction with other programming languages. When the native method is called, it enters a completely new world that is no longer limited by virtual machines. Therefore, it is easy to see nativeheapoutofmemory, which is not controlled by JVM.

Runtimedataarea component:

This is what we often call JVM memory. It is mainly divided into five parts --

1. Heap: Only one heap space exists in a Java virtual instance.

2. methodarea (method region): information about the mounted class is stored in the memory of methodarea. When a virtual machine loads a type, it uses the class loader to locate the corresponding class file, then reads the class file content and transmits it to the virtual machine.

3. javastack (java stack): The Virtual Machine only performs two operations on javastack directly: frame-based pressure stack or outbound stack.

4. programcounter: Each thread has its own PC register, which is also created when the thread is started. The content of the PC register always points to the next address that will be executed. The address here can be a local pointer or offset corresponding to the start instruction of the method in the method area.

5. nativemethodstack: the address for saving the native method to enter the Region

The above five parts are used only by the sharing of heap and methodarea, while javastack, programcounter, and nativemethodstack are thread-specific and each thread has its own part. This section briefly introduces the JVM memory structure.

Address: http://developer.51cto.com/art/201009/227977.htm