JVM Tuning and Optimization Guide

Introduction to JVM Tuning

JVM tuning is a critical aspect of Java application performance optimization. This guide covers essential JVM parameters, garbage collection strategies, and best practices for optimizing Java applications.

Memory Management

Heap Memory Configuration


# Basic heap size settings
-Xms2g -Xmx2g

# Setting initial and maximum heap size
-XX:InitialRAMPercentage=70.0
-XX:MaxRAMPercentage=70.0

# Setting minimum and maximum heap size
-XX:MinHeapSize=512m
-XX:MaxHeapSize=2g

Metaspace Configuration


# Metaspace settings
-XX:MetaspaceSize=256m
-XX:MaxMetaspaceSize=512m

Garbage Collection Tuning

G1 Garbage Collector


# Enable G1 GC
-XX:+UseG1GC

# G1 specific settings
-XX:G1HeapRegionSize=16m
-XX:MaxGCPauseMillis=200
-XX:G1ReservePercent=10

Z Garbage Collector


# Enable ZGC
-XX:+UseZGC

# ZGC specific settings
-XX:ZCollectionInterval=5
-XX:ZAllocationSpikeTolerance=2.0

Thread and Concurrency Tuning


# Thread stack size
-Xss1m

# Thread pool settings
-XX:ThreadStackSize=1024
-XX:ThreadPriorityPolicy=0

JIT Compilation Tuning


# JIT compilation settings
-XX:+TieredCompilation
-XX:TieredStopAtLevel=1
-XX:CompileThreshold=1000

Monitoring and Diagnostics

GC Logging


# GC logging settings
-Xlog:gc*:file=gc.log:time,uptime:filecount=5,filesize=20M

Flight Recorder


# Enable Flight Recorder
-XX:StartFlightRecording=duration=60s,filename=recording.jfr

Best Practices for JVM Tuning

  • Start with minimal tuning and measure performance
  • Use appropriate garbage collector for your workload
  • Monitor GC logs and adjust parameters accordingly
  • Consider application-specific requirements
  • Regular performance testing and monitoring

Common Issues and Solutions

Out of Memory Errors

  • Increase heap size
  • Check for memory leaks
  • Optimize object creation

GC Pauses

  • Adjust GC parameters
  • Consider using low-pause collectors
  • Optimize object lifetime

JVM Tuning Tools

  • JConsole - Basic monitoring
  • VisualVM - Advanced monitoring
  • Java Flight Recorder - Detailed profiling
  • GCViewer - GC log analysis

Conclusion

Effective JVM tuning requires understanding your application's behavior and requirements. Start with basic tuning and gradually optimize based on monitoring data and performance metrics. Remember that tuning is an iterative process that requires regular monitoring and adjustment.