Performance Limitations of the Java Core Libraries

Unlike applets, traditional systems programs written in Java place significant demands on the Java runtime and core libraries, and their performance is often critically important. This paper describes our experiences using Java to build such a systems program, namely, a scalable web crawler. We found that our runtime, which includes a just-in-time compiler that compiles Java bytecodes to native machine code, performed well. However, we encountered several performance problems with the Java 1.1 core libraries, including excessive synchronization, excessive allocation, and other programming inefficiencies. The paper describes the most serious pitfalls and how we programmed around them. In total, these workarounds more than doubled the speed of our crawler.