Java Performance Companion

Charlie Hunt, is a JVM Performance Engineer at Oracle where he works on the performance of Java SE, Java EE, Java HotSpot VM, and Java SE class libraries. He presents on Java performance at various events, including JavaOne, QCon, Velocity, and Dreamforce, and he coauthored Java Performance (Addison-Wesley, 2012). Monica Beckwith is an independent performance consultant optimizing customer applications for server class systems running the Java Virtual Machine. She has worked with Java HotSpot VM optimising the JIT Compiler, the generated code, the JVM heuristics and garbage collection and collectors. Monica led Oracle’s Garbage First Garbage Collector performance team and was named a JavaOne Rock Star. Poonam Parhar is a JVM Sustaining Engineer at Oracle, where her primary responsibility is to resolve customer-escalated problems against Oracle JRockit and Java HotSpot VMs. She loves debugging and troubleshooting problems, and is always focused on improving the serviceability and supportability of the JVM. Bengt Rutisson is a JVM Engineer at Oracle, working in the HotSpot VM team. He has worked on garbage collections in JVMs for the past ten years, first with the Oracle JRockit VM and the last six years with the Java HotSpot VM. Bengt is an active participant in the OpenJDK project, with many contributions of features, stability fixes and performance enhancements.

• Preface ixAcknowledgments xiAbout the Authors xv  Chapter 1: Garbage First Overview 1Terminology 1Parallel GC 2Serial GC 4Concurrent Mark Sweep (CMS) GC 5Garbage First (G1) GC 8References 14 Chapter 2: Garbage First Garbage Collector in Depth 15Background 15Garbage Collection in G1 16The Young Generation 17A Young Collection Pause 18Object Aging and the Old Generation 19Humongous Regions 19A Mixed Collection Pause 22Collection Sets and Their Importance 24Remembered Sets and Their Importance 24Concurrent Marking in G1 GC 30Stages of Concurrent Marking 34Evacuation Failures and Full Collection 37References 38  Chapter 3: Garbage First Garbage Collector Performance Tuning 39The Stages of a Young Collection 39Young Generation Tunables 50Concurrent Marking Phase Tunables 52A Refresher on the Mixed Garbage Collection Phase 54The Taming of a Mixed Garbage Collection Phase 56Avoiding Evacuation Failures 59Reference Processing 60References 65  Chapter 4: The Serviceability Agent 67What Is the Serviceability Agent? 68Why Do We Need the SA? 68SA Components 69SA Binaries in the JDK 69JDK Versions with Complete SA Binaries 69How the SA Understands HotSpot VM Data Structures 70SA Version Matching 71The Serviceability Agent Debugging Tools 72Core Dump or Crash Dump Files 108Debugging Transported Core Files 109System Properties for the Serviceability Agent 111Environment Variables for the Serviceability Agent 112JDI Implementation 113Extending Serviceability Agent Tools 115Serviceability Agent Plugin for VisualVM 117Troubleshooting Problems Using the SA 123  Appendix: Additional HotSpot VM Command-Line Options of Interest 145   Index 155