Java Performance

Scott Oaks

Mentioned 1

Coding and testing are often considered separate areas of expertise. In this comprehensive guide, author and Java expert Scott Oaks takes the approach that anyone who works with Java should be equally adept at understanding how code behaves in the JVM, as well as the tunings likely to help its performance. You’ll gain in-depth knowledge of Java application performance, using the Java Virtual Machine (JVM) and the Java platform, including the language and API. Developers and performance engineers alike will learn a variety of features, tools, and processes for improving the way Java 7 and 8 applications perform. Apply four principles for obtaining the best results from performance testingUse JDK tools to collect data on how a Java application is performingUnderstand the advantages and disadvantages of using a JIT compilerTune JVM garbage collectors to affect programs as little as possibleUse techniques to manage heap memory and JVM native memoryMaximize Java threading and synchronization performance featuresTackle performance issues in Java EE and Java SE APIsImprove Java-driven database application performance

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For my current project, i try to use Atomic Integers and Atomic Booleans where ever possible when we have more than 1 thread accessing it. This helps in keeping the logic lock free(Internally i know it may still use locks) and the code much cleaner. The use case is mostly for configuration tags which may change abruptly.

I want to know what is the penalty performance wise of using Atomic Variables, will this invalidate the cache far too often and actually make my solution inferior than just using locks?

atomic* classes does not use locks, it uses CAS (compare-and-set) to achieve thread-safety. in general they are faster then locking variant, however under very high contention they tends to be actually slower. if you want some analogy, it is something like optimistic and pessimistic locking in DB.

if you are interested in more details, you might want to check Java Performance: The Definitive Guide book.

ADD: With cache I assume you are referring to happens-before relationship. Here is quote from oracle tutorial:

The java.util.concurrent.atomic package defines classes that support atomic operations on single variables. All classes have get and set methods that work like reads and writes on volatile variables. That is, a set has a happens-before relationship with any subsequent get on the same variable.