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 ix

Acknowledgments xi

About the Authors xv

 

Chapter 1: Garbage First Overview 1

Terminology 1

Parallel GC 2

Serial GC 4

Concurrent Mark Sweep (CMS) GC 5

Garbage First (G1) GC 8

References 14




Chapter 2: Garbage First Garbage Collector in Depth 15

Background 15

Garbage Collection in G1 16

The Young Generation 17

A Young Collection Pause 18

Object Aging and the Old Generation 19

Humongous Regions 19

A Mixed Collection Pause 22

Collection Sets and Their Importance 24

Remembered Sets and Their Importance 24

Concurrent Marking in G1 GC 30

Stages of Concurrent Marking 34

Evacuation Failures and Full Collection 37

References 38

 

Chapter 3: Garbage First Garbage Collector Performance Tuning 39

The Stages of a Young Collection 39

Young Generation Tunables 50

Concurrent Marking Phase Tunables 52

A Refresher on the Mixed Garbage Collection Phase 54

The Taming of a Mixed Garbage Collection Phase 56

Avoiding Evacuation Failures 59

Reference Processing 60

References 65

 

Chapter 4: The Serviceability Agent 67

What Is the Serviceability Agent? 68

Why Do We Need the SA? 68

SA Components 69

SA Binaries in the JDK 69

JDK Versions with Complete SA Binaries 69

How the SA Understands HotSpot VM Data Structures 70

SA Version Matching 71

The Serviceability Agent Debugging Tools 72

Core Dump or Crash Dump Files 108

Debugging Transported Core Files 109

System Properties for the Serviceability Agent 111

Environment Variables for the Serviceability Agent 112

JDI Implementation 113

Extending Serviceability Agent Tools 115

Serviceability Agent Plugin for VisualVM 117

Troubleshooting Problems Using the SA 123

 

Appendix: Additional HotSpot VM Command-Line Options of Interest 145

 



Index 155