Java Locks: Analysis and Acceleration by

This dissertation presents several techniques to accelerate Java locks based on the analyses of their behavior from various viewpoints. Ten years have passed since Java was announced, and now the language has come to be used in various fields including large-scale Web services. To make such applications practical, performance improvements for the Java execution environments are indispensable. In Java, the language directly supports parallel processing, and lock operations are executed very frequently. Their overhead is considerable. For example, one report said that 1/5 of the execution time was consumed by lock processing in an early Java environment. Therefore, accelerating Java locks has been very important to make Java environments run faster. From the analysis of locks in various Java applications, we discovered that most contentions are temporary in Java. To exploit this contention transience, this dissertation presents a new method for Java locks, in which a lock can be acquired with just one atomic operation in the absence of contention. The method, called tasuki lock, increased the performance of Java application by up to 13.1%, and is used by IBM’s production Java virtual machines. Next, uncontended Java locks were also analyzed, and it turned out that for many objects, the lock is acquired primarily by a specific thread. By exploiting the thread locality, this dissertation proposes a novel technique of reserving locks for threads. With the reservation lock, the reservation-owner thread can acquire a lock without any atomic operations, and the performance was further improved by up to 53%. This dissertation also presents an improvement of the reservation lock, where the reservation is not canceled and the owner thread can always acquire its locks very quickly. In this asymmetric lock, we observed a performance improvement of up to 7.9%. A unique methodology for introducing a new feature into Java locks is also used in this algorithm. The main contributions of this dissertation are: the findings about new characteristics of Java locks, the proposals of new lock methods that exploit these characteristics, and their implementation and evaluation on a state-of-the-art Java system.