The Java memory model is fatally flawed

The Java memory model described in Chapter 17 of the Java Language Specification gives constraints on how threads interact through memory. This chapter is hard to interpret and poorly understood; it imposes constraints that prohibit common compiler optimizations and are expensive to implement on existing hardware. Most JVMs violate the constraints of the existing Java memory model; conforming to the existing specification would impose significant performance penalties. In addition, programming idioms used by some programmers and used within Sun's Java Development Kit is not guaranteed to be valid according the existing Java memory model. Furthermore, implementing Java on a shared memory multiprocessor that implements a weak memory model poses some implementation challenges not previously considered.

• Type: Journal
• Year: 2000
• Where: CONCURRENCY
• Authors: William Pugh
• Keywords: Common Compiler Optimizations, CONCURRENCY 2000, Java Language Specification, Java Memory Model