Book Image

Oracle JRockit: The Definitive Guide

Book Image

Oracle JRockit: The Definitive Guide

Overview of this book

Oracle JRockit is one of the industry’s highest performing Java Virtual Machines. Java developers are always on the lookout for better ways to analyze application behavior and gain performance. As we all know, this is not as easy as it looks. Welcome to JRockit: The Definitive Guide.This book helps you gain in-depth knowledge of Java from the JVM’s point of view. We will explain how to write code that works well with the JVM to gain performance and scalability. Starting with the inner workings of the JRockit JVM and finishing with a thorough walkthrough of the tools in the JRockit Mission Control suite, this book is for anyone who wants to know more about how the JVM executes your Java application and how to profile for better performance.
Table of Contents (23 chapters)
Oracle JRockit
Credits
Foreword
About the Authors
Acknowledgement
About the Reviewers
Preface
12
Using the JRockit Management APIs
Bibliography
Glossary
AST
CAS
HIR
IR
JFR
JMX
JRA
JSR
LIR
MD5
MIR
PDE
RCP
SWT
TLA
Index

Speeding it up and making it scale


This section addresses what a modern runtime can do to speed up memory management, going from impractical and "academic" algorithms to real world performance.

Thread local allocation

One technique, used in JRockit, that significantly speeds up object allocation is the concept of thread local allocation. It is normally much cheaper to allocate an object locally in a buffer in the running Java thread than going through the synchronized process of placing it directly on the heap. A naive garbage collector doing direct heap allocations would need a global heap lock for each allocation. This would quickly be the site for a nightmarish amount of contention. On the other hand, if each Java thread keeps a thread local object buffer, most object allocations may be implemented simply as the addition of a pointer, one assembly instruction on most hardware platforms. We refer to these thread local buffers as Thread Local Areas (TLA). The TLAs naturally have to processed...