Azul Zulu is a popular OpenJDK distribution used throughout this site, especially for Raspberry Pi and embedded Java setups. These posts cover installation, version upgrades, and platform-specific builds.
Originally posted on the Pi4J website.
Dieter Holz was experimenting with Pi4J V3 on a Raspberry Pi Zero 2. Because this version requires Java 21 or newer, he upgraded his OS to a newer Java version and found out that no Java code could be executed. He tried with Java 21 and 24, and neither worked correctly, although Java 17 runs without problems.
Last week I was working on a blog post about Azul Zulu with JavaFX support for ARM systems, like the Raspberry Pi. As you can see in this video, I found out my little test application with a lot of “bouncing balls” started losing performance on the Raspberry Pi with more than 1000 of those balls.
On July 15th of 2023, I published a post here about my initial experiments with CRaC on the Raspberry Pi. At that time, I found out that both the Linux kernel in Raspberry Pi OS and the Zulu Build of OpenJDK still needed some changes to work on the Raspberry Pi. I created a ticket in the Linux kernel project, which was solved by Phil Elwell. Last week, a new version of the Raspberry Pi OS, based on Debian Bookworm, was released. And in september, version 21 of OpenJDK was released and the Zulu Build of it, includes CRaC. So let’s see if we can use CRaC without issues, if we bring all this togheter.
With the April release of the Zulu Build of OpenJDK, Azul announced the integration of CRaC in its version 17 of Java for Linux. Coordinated Restore at Checkpoint (CRaC) is a feature introduced in OpenJDK to improve Java’s application startup and warmup times to milliseconds from seconds or even minutes, by allowing a running application to pause, snapshot its state, and restart later, even on a different machine.