O’reilly - Java Performance Tuning
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Preface
Performance has been an important issue with Java™ since the first version hit the Web years ago.
Making those first interpreted programs run fast enough was a huge challenge for many developers.
Since then, Java performance has improved enormously, and any Java program can now be made to
run fast enough provided you avoid the main performance pitfalls.
This book provides all the details a developer needs to performance-tune any type of Java program.
I give step-by-step instructions on all aspects of the performance-tuning process, right from early
considerations such as setting goals, measuring performance, and choosing a compiler, to detailed
examples on using profiling tools and applying the results to tune the code. This is not an entry-
level book about Java, but you do not need any previous tuning knowledge to benefit from reading
it.
Many of the tuning techniques presented in this book lead to an increased maintenance cost, so they
should not be applied arbitrarily. Change your code only when a bottleneck has been identified, and
never change the design of your application for minor performance gains.
Contents of This Book
Chapter 1 gives general guidelines on how to tune. If you do not yet have a tuning strategy, this
chapter provides a methodical tuning process.
Chapter 2 covers the tools you need to use while tuning. Chapter 3 looks at the Java Development
Kit™ ( JDK, now Java SDK), including VMs and compilers.
Chapter 4 through Chapter 12 cover various techniques you can apply to Java code. Chapter 12
looks at tuning techniques specific to distributed applications.
Chapter 13 steps back from the low-level code-tuning techniques examined throughout most of the
book and considers tuning at all other stages of the development process.
Chapter 14 is a quick look at some operating system-level tuning techniques.
Each chapter has a performance tuning checklist at its end. Use these lists to ensure that you have
not missed any core tuning techniques while you are tuning.
Virtual Machine (VM) Versions
I have focused on the Sun VMs since there is enough variation within these to show interesting
results. I have shown the time variation across different VMs for many of the tests. However, your
main focus should be on the effects that tuning has on any one VM, as this identifies the usefulness
of a tuning technique. Differences between VMs are interesting, but are only indicative and need to
be verified for your specific application. Where I have shown the results of timed tests, the VM
versions I have used are:
1.1.6
Version 1.1.x VMs do less VM-level work than later Java 2 VMs, so I have used a 1.1.x VM
that includes a JIT. Version 1.1.6 was the earliest 1.1.x JDK that included enough
optimizations to be a useful base. Despite many later improvements throughout the JDK, the
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