Java GC & Memory Management
Dive into the technical core of the Minecraft engine. Learn how Java manages memory and how to tune Garbage Collection for zero-lag gameplay.
1. Introduction to the JVM
Minecraft is written in Java, which runs inside a Java Virtual Machine (JVM). As of 2026, Java 25 is the standard for high-performance servers. Unlike older versions, Java 25 includes radical improvements to how the system manages memory, making many manual optimizations from the past decade obsolete.
2. Understanding the Heap
The "Heap" is the memory space allocated to your Minecraft server. When you set your server to 6GB of RAM on Deduck, you are setting the maximum size of the Java Heap.
- Xms: The starting amount of RAM allocated. In modern setups, setting Xms equal to Xmx (e.g., -Xms6G -Xmx6G) is recommended to prevent memory allocation jitter.
- Xmx: The maximum amount of RAM the server can use.
- ZGC (Z Garbage Collector): While G1GC is the default, ZGC has become viable for large servers in 2026, offering sub-millisecond pause times.
3. The Evolution of GC Algorithms
In 2026, the two primary collectors are:
- G1GC: The default and most stable. In Java 25, it features "Dynamic Heap Sizing" that adjusts to server load in real-time.
- Generational ZGC: The cutting edge. It is designed for massive heaps (16GB+) and keeps lag spikes effectively at zero, though it requires slightly more CPU overhead.
4. The "High RAM" Trap
It remains true that giving a server too much RAM can be counterproductive. In Java 25, while the G1GC is better at handling large heaps, we still recommend giving only what you need. A typical Folia server with 50-100 players thrives on 10GB to 12GB. Overshooting to 32GB can still cause unnecessary background scanning.
5. Monitoring with JFR (Java Flight Recorder)
For deep diagnostics, modern admins use JFR. It is built directly into the JVM and can be started via Spark (/spark jfr start). It provides a low-overhead, millisecond-by-millisecond view of GC events, object allocations, and CPU sampling.
6. Tuning for the Future
The trend in 2026 is Simplicity. With the JVM getting smarter, the best advice is to let Java do its job. On Deduck, we stay updated with the latest OpenJDK builds to ensure your server always benefits from the latest memory management patches without you having to touch a single config line.