Symptoms: A lag spike every few seconds, the server freezes, periodic stuttering

Possible Causes

  • Garbage Collection pauses
  • Automatic saving (autosave)
  • Chunk generation load
  • Bad JVM flags

Step-by-Step Fix

Step 1

Use Aikar's JVM flags

bash
java -Xms10G -Xmx10G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -jar server.jar nogui

Step 2

Pre-generate the world

bash
/chunky radius 5000
/chunky start

Step 3

Run a GC analysis with the Spark profiler

bash
/spark gc

Step 4

Increase the autosave interval (paper.yml)

bash
max-auto-save-chunks-per-tick: 8