Fixing the Java memory model

The Java memory model described in Chapter 17 of the Java Language Specification gives constraints on how threads interact through memory. The Java memory model is hard to interpret and poorly understood; it imposes constraints that prohibit common compiler optimizations and are expensive to implement on existing hardware. At least one shipping optimizing Java compiler violates the constraints of the existing Java memory model. These issues are particularly important for high-performance Java applications, since they are more likely to use and need aggressive optimizing compilers and parallel processors. In addition, programming idioms used by some programmers and used within Suns Java Development Kit is not guaranteed to be valid according the existing Java memory model. This paper reviews these issues and suggests replacement memory models for Java. 1 Introduction The Java memory model, as described in chapter 17 of the Java Language Specification GJS96, is very hard to unders...