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About ReadyNow!

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Looking for Zing? The Azul Zing Virtual Machine is now Azul Zulu Prime Builds of OpenJDK and part of Azul Platform Prime. Learn more.

What is ReadyNow!?

ReadyNow! is a feature of Azul Platform Prime that, when enabled, dramatically improves the warm-up behavior of the application.

What is Warm-Up?

Warm-up is the time taken for the Java application to reach optimal performance. It is the task of the Just-in-Time (JIT) compiler to deliver optimal performance by producing optimized compiled code from application bytecode. This process takes time as the JIT compiler seeks optimization opportunities based upon profiling of the application.

How Does ReadyNow! Work?

ReadyNow! persists the profiling information gathered during the run of the application so that subsequent runs do not have to learn again from scratch. Warm-up improves each application run until optimal performance is reached.

Figure 1. ReadyNow! Performance Improvement

ReadyNow! Performance Improvement

Running ReadyNow!

To enable ReadyNow!, add the following command-line options, where <file> is typically the same for both:

  • -XX:ProfileLogIn=<file> instructs Azul Platform Prime to use information from an existing profile log.

  • -XX:ProfileLogOut=<file> records the previous compilation and the deoptimization decisions from the run.

Running the application will then automatically generate or update a profile log. This profile log will be consumed upon subsequent runs of the application, improving warm-up.