About The Safepoint

The Safepoint is an independent English-language publication of practical guides for people who run Java and other JVM applications in production: developers on call, SREs and platform engineers.

What we publish

Guides that start from a production symptom (an error message, a memory graph that keeps climbing, a process stuck at full CPU) and end with commands to run and decisions to make. The topics are the JVM's own diagnostic and tuning surface: heap and off-heap memory, garbage collectors and their logs, threads and locks, containers, and JDK Flight Recorder.

The name comes from the JVM itself. A safepoint is a point at which all application threads are stopped so the JVM can perform an operation that needs a consistent view of the program, such as many garbage collection pauses or a thread dump. It is where the JVM looks at itself; that is what these guides try to do too.

How the guides are checked

• Primary sources only. Option names, defaults and behaviours come from the java, jcmd, jstat and jfr reference pages, the HotSpot Garbage Collection Tuning Guide, the Java Platform Troubleshooting Guide, the javadoc, JDK Enhancement Proposals (JEPs) and the OpenJDK source code. Each guide lists its sources.
• Versions are named. JVM defaults change between releases. When a statement depends on the release, the guide says which one introduced or changed the behaviour.
• No invented numbers. We do not publish benchmark results we did not run, or "typical" overhead figures without a documented source. Sample log lines and outputs are labelled as illustrative.
• Corrections. Guides are revised when the documentation changes or an error is found; a revised guide shows the date of the revision under its title.

What we do not do

• We do not sell tools, training or consulting, and no guide is sponsored.
• We are not affiliated with Oracle, the OpenJDK project, the Eclipse Foundation or any JDK vendor. Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates; other names belong to their owners.
• We cannot see your system. Flags that help one workload can hurt another: test changes under realistic load and change one option at a time.

The site sets no cookies and uses no analytics or advertising trackers. Photographs are free-licensed; see the photo credits.

About this domain

From roughly 2013 to 2018, the domain hellojava.info hosted a Chinese-language technical blog about Java and JVM problems in production, which other developers often linked to. It later became a parking page. The Safepoint is a new, independent English-language publication with no connection to the people or organisation behind that blog. No text, image or other content from the former site has been reused. Old links to the former site's tag, category and archive pages lead to the closest guides here.