Output directory based on In-depth Understanding of the JVM

  • Summary of the JVM – 01
  • JVM-02 class loading subsystem
  • Jvm-03 Runtime Data area – [application counter + Vm stack + local method stack + Local method]
  • Jvm-04 Runtime Data area – [heap + method area + object instantiation memory layout and access location + direct memory]
  • Jvm-05 execution engine + String constant pool StringTable
  • Jvm-06 Garbage Collector

preface

Note: Based on a personal output from Understanding the JVM in Depth – 2nd edition – by Chi-ming Chou, this article will be referred to in the page number of the book. B station university related video link address, thank Song Shi. Reference big brother blog link address, thank big brother.

1. The description of the JVM

1.1 some JVM

  • SUN Classic
  • HotSpot VM: HotSpot code detection technology
  • BEA JRockit (BEA acquired by Oracle), one of the fastest JVMS in the world
  • TaoBao JVM: TaoBao Tmall is launched to replace Oracle’s official JVM
  • .

Book P3-P16: Java History + Various VMS

1.2 Location of the JVM

1.3 Java code execution process

Java programs –(compiled)– > bytecode files –(interpreted execution)– > Operating systems (Win, Linux, Mac).java source files are compiled by a front-end compiler (such as Javac) into.class bytecode files, which are interpreted and executed by a back-end compiler (JVM).

1.4 Architectural model of the JVM

  • Due to the cross-platform design, Java instructions are designed on a stack. The stack is zero-address instruction (only out and on the stack), and the execution depends on the operation stack.
  • Stack: Small set of instructions, many instructions (frequent in and out operations), easy to implement by the compiler. But the execution performance is worse than the register.
  • Register: few instructions

Q: Why not replace the register with higher performance? A: Because of the cross-platform design, Java instructions are designed according to the stack. Different platforms have different CPU architectures, so it cannot be register-based.

1.5 Lifecycle of the JVM

1. Start the

  • This is done by bootstrap class Loader to create an initial class, specified by the JVM’s implementation

2. Perform

  • Execute Java programs; It runs when the program begins and stops when the program ends. When you execute a Java program, you’re really executing a process called the Java Virtual Machine

3. Quit

  • The program completes normally
  • The program ends abnormally with an exception or error
  • An operating system error caused the termination
  • Call the Halt method of the Runtime class or exit method of the System class

1.6 JVM Architecture Overview

Output directory based on In-depth Understanding of the JVM

  • Summary of the JVM – 01
  • JVM-02 class loading subsystem
  • Jvm-03 Runtime Data area – [application counter + Vm stack + local method stack + Local method]
  • Jvm-04 Runtime Data area – [heap + method area + object instantiation memory layout and access location + direct memory]
  • Jvm-05 execution engine + String constant pool StringTable
  • Jvm-06 Garbage Collector