JVM performance: OpenJ9 uses least memory. GraalVM most. OpenJDK distributions differ.

In a previous blog post I created a setup to compare JVM performance of several JVMs. I received some valuable feedback on the measures I conducted and requests to add additional JVMs. In this second post I'll look at some more JVMs and I've added some measures like process memory usage and startup time. Also I've automated the test and reduced the complexity of the setup by removing haproxy and testing a single JVM at a time.

Comparing JVM performance; Zulu, OpenJDK, Oracle JDK, GraalVM CE

There are many different choices for a JVM for your Java application. Which would be the best to use? This depends on various factors. Performance being an important one. Solid performance research however is difficult. In this blog post I'll describe a setup I created to perform tests on different JVMs at the same time and show some interesting results! I also looked at the effect of resource isolation (assigning specific CPUs and memory to the process). This effect was negligible. My test application consisted of a reactive (non-blocking) Spring Boot REST application and I've used Prometheus to poll the JVMs and Grafana for visualization.

Below is an image of the used setup. Everything was running in Docker containers except SoapUI.

Running Spring Boot in a Docker container on OpenJDK, Oracle JDK, Zulu on Alpine Linux, Oracle Linux, Ubuntu

Spring Boot is great for running inside a Docker container. Spring Boot applications 'just run'. A Spring Boot application has an embedded servlet engine making it independent of application servers. There is a Spring Boot Maven plugin available to easily create a JAR file which contains all required dependencies. This JAR file can be run with a single command-line like 'java -jar SpringBootApp.jar'. For running it in a Docker container, you only require a base OS and a JDK. In this blog post I'll give examples on how to get started with different OSs and different JDKs in Docker. I'll finish with an example on how to build a Docker image with a Spring Boot application in it.