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A distributed Java Virtual Machine (DJVM) spanning multiple cluster nodes can provide a true parallel execution environment for multi-threaded Java applications. Most existing DJVMs suffer from the slow Java execution in interpretive mode and thus may not be efficient enough for solving computation-intensive problems. We present JESSICA2, a new DJVM running in JIT compilation mode that can execute multi-threaded Java applications transparently on clusters. JESSICA2 provides a single system image (SSI) illusion to Java applications via an embedded global object space (GOS) layer. It implements a cluster-aware Java execution engine that supports transparent Java thread migration for achieving dynamic load balancing. We discuss the issues of supporting transparent Java thread migration in a JIT compilation environment and propose several lightweight solutions. An adaptive migrating-home protocol used in the implementation of the GOS is introduced. The system has been implemented on x86-based Linux clusters and significant performance improvements over the previous JESSICA system have been observed.
Date of Conference: 2002