Java 10 introduced an exciting new feature called “Code-based JIT compilation” which aims to improve the performance and runtime efficiency of Java applications. Just-In-Time (JIT) compilation is a technique used by Java to improve performance by dynamically converting Java bytecode to native machine code during runtime. With the introduction of Code-based JIT compilation, Java 10 takes it a step further by optimizing the generated machine code for better performance.

What is JIT compilation?

Just-In-Time (JIT) compilation is a process where the Java Virtual Machine (JVM) dynamically compiles the Java bytecode into native machine code just before the execution of a method. It helps to improve the performance of Java applications by optimizing the code based on runtime information.

How does Code-based JIT compilation work?

Code-based JIT compilation in Java 10 focuses on optimizing the generated machine code by applying advanced techniques such as profile-guided optimization (PGO). PGO collects runtime information about the application’s execution patterns and optimizes the code accordingly.

The process of Code-based JIT compilation involves the following steps:

1. JVM loads the Java bytecode and interprets it initially.
2. As the JVM encounters frequently executed methods, it triggers JIT compilation for those methods.
3. The JIT compiler analyzes the bytecode and generates an optimized version of the machine code.
4. The JVM replaces the interpreted code with the optimized machine code in the runtime environment.
5. The application continues its execution with the optimized code, resulting in improved performance.

Benefits of Code-based JIT compilation

Code-based JIT compilation brings several benefits to Java applications:

1. Improved runtime performance: By optimizing the machine code based on runtime profiling, Code-based JIT compilation significantly improves the performance of Java applications.
2. Better utilization of hardware: The optimized machine code takes advantage of hardware capabilities, such as vectorization and parallelism, resulting in better utilization of the underlying hardware resources.
3. Reduced startup time: The JVM can start executing optimized machine code right from the beginning, minimizing the warm-up time required for performance optimization.

Example code

To enable Code-based JIT compilation in Java 10, you don’t need to make any specific changes to your code. The JVM automatically handles the compilation and optimization process. However, you can monitor the performance improvements by comparing the execution time before and after enabling Code-based JIT compilation.

public class Main {
  public static void main(String[] args) {
    long startTime = System.nanoTime();
    
    // Execute your application code here
    
    long endTime = System.nanoTime();
    long executionTime = endTime - startTime;

    System.out.println("Execution time: " + executionTime + " ns");
  }
}

Conclusion

Code-based JIT compilation in Java 10 brings significant performance improvements to Java applications. With its ability to optimize the generated machine code based on runtime information, it provides better runtime performance, better hardware utilization, and reduced startup time. By enabling Code-based JIT compilation in your Java applications, you can take advantage of these benefits and enhance the overall performance of your applications.

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