Help weave the Loom

OpenJDK update: Early access Loom builds available

Sarah Schlothauer
© Shutterstock / Maryana Volkova

Welcome to the newest milestone for Project Loom. Early access for Loom builds are now available, according to the OpenJDK mailing list. Find out what feedback will be helpful to bring this project closer to stability. Project Loom is intended to help with scalability, performance, and delivering Java VM features and APIs.

The JDK and Project Loom hit a new milestone. According to Oracle’s Ron Pressler on July 29, 2019, in the OpenJDK mailing list, Early Access OpenJDK binaries that include Project loom are now available for download.

Let’s take a quick look at what this project is and what kind of user feedback will help it grow.

Project Loom

What is Project Loom? From to the OpenJDK Wiki, “Project Loom is intended to explore, incubate and deliver Java VM features and APIs built on top of them for the purpose of supporting easy-to-use, high-throughput lightweight concurrency and new programming models on the Java platform”.

It uses lightweight user-mode threads called Fibers. Fibers allow for scheduling synchronous code. Read more about the Structured Concurrency method and its benefits that Project Loom explores.

SEE ALSO: Infrastructure as Code – Lessons learned from Dev to Ops

For more information about the project, watch this 2018 video from Java with Oracle’s Ron Pressler and Alan Bateman. In the video, they discuss the project, its implementation and design, and show a demo.

Giving feedback

For those interested in helping out, you can help this project reach maturity. Test out the current prototype. Project Loom is currently under active development and is not stable. Any user feedback and notification of bugs and/or issues will be helpful for future improvements and releases.

The announcement states that the best way to help is by downloading the early access binaries and simply testing it out.

SEE ALSO: SysAdmin Appreciation Day: “This is broken. Can you fix it?”

In the OpenJDK mailing list, Pressler notes:

We are mostly interested in feedback on the following:

– Given current Loom limitations (such as held monitors pinning threads), how hard
is it to migrate existing code to work well with fibers?
– Structured concurrency: is it helpful? What can be improved?
– Which use cases are important to you, and are they well-served by Loom?

A small write-up about your specific use cases for Project Loom will help.

Current missing features include:

  • Yielding while a native VM frame is on the stack in the case of a priviliged action, reflective invocation and MethodHandle invocation.
  • Cloning continuations
  • Serialization of fiber/continuation

Information on how to download available here. Currently, Loom supports Mac and Linux x86-64. Source code available here.

All info subject to change as the project evolves.

Sarah Schlothauer

Sarah Schlothauer

All Posts by Sarah Schlothauer

Sarah Schlothauer is the editor for She received her Bachelor's degree from Monmouth University, West Long Branch, New Jersey. She currently lives in Frankfurt, Germany with her husband and cat where she enjoys reading, writing, and medieval reenactment. She is also the editor for Conditio Humana, an online magazine about ethics, AI, and technology.

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