The Marmot system is a research platform for studying the implementation of high level programming languages. It currently comprises an optimizing native-code compiler, runtime system, and libraries for a large subset of Java. Marmot integrates well-known representation, optimization, code generation, and runtime techniques with a few Java-specific features to achieve competitive performance. This paper contains a description of the Marmot system design, along with highlights of our experience applying and adapting traditional implementation techniques to Java. A detailed performance evaluation assesses both Marmot's overall performance relative to other Java and C++ implementations, and the relative costs of various Java language features in Marmot-compiled code. Our experience with Marmot has demonstrated that well-known compilation techniques can produce very good performance for static Java applicationscomparable or superior to other Java systems, and approaching that of C++ in some cases.We seek to bring the benefits of Java's high level features to larger programs while minimizing the associated performance penalty. Our approach is to adapt well-known implementation techniques from existing language implementations to Java, integrating them with new Java-specific technology where necessary. We have constructed a system, Marmot, that includes a static optimizing compiler, runtime system, and libraries for a large subset of Java. The native-code compiler implements standard scalar optimizations of the sort found in Fortran, C and C++ compilers [2] and basic object-oriented optimizations such as call binding based on class hierarchy analysis [3,4]. It uses modern representation techniques such as SSA form and type-based compilation [5,6] to improve optimization and to support precise garbage collection. The runtime system supports multithreading, efficient synchronization and exception mechanisms, and several garbage collectors, including a precise generational collector. Marmot is implemented almost entirely in Java, and is one of its own most demanding test cases.Our experience with Marmot demonstrates that well-known compilation techniques can produce very good performance for static Java applications -comparable or superior to other Java systems, and approaching that of C++ in some cases. Marmot reduces the costs of safety checks in many programs to a modest 5-10 per cent of execution time. Synchronization costs can be quite significant, and optimization techniques to reduce these costs are worth pursuing. Recognizing single threaded programs and optimizing them accordingly can be an important special case. Although Marmot includes a quality generational collector and further reduces the cost of storage by allocating objects with appropriately bounded lifetimes and statically known sizes on the stack, storage management costs can still be significant.We begin this paper by describing and motivating the subset of Java supported by Marmot. Sections 3-5 describe the design and implementation of the native-cod...

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Many garbage-collected systems use a single garbage collection algorithm across all applications. It has long been known that this can produce poor performance on applications for which that collector is not well suited. In some systems, such as those that execute stand-Mone compiled executables, an appropriate collector for each application can be selected from a pool of available collectors and tuned by using profile information. In a study of 20 benchmarks and several collectors, compiled with the Marmot optimizing Java-to-native compiler, for every collector there was at least one benchmark that would have been at least 15% faster with a more appropriate collector. The collectors are a copying collector, a generational copying collector, which is combined with each of 4 different write barriers, and the null collector, which allocates but never collects. A detailed analysis of storage management costs shows how they vary by application and collector.

Tiger is a scalable, fault-tolerant video file server constructed from a collection of computers connected by a switclied network., All content files are striped across all of the computers and disks in a Tiger system. In order to prevent conflicts for a particular resource between two viewers, Tiger schedules viewers so that ihey do not require access to the same resource at the same time. In the abstract, there is a single, global schedule that describes all of the viewers in the system. In practice, the schedule is distrib&d among all of the computers in the system, each of which has a possibly partially inconsistent view of a subset of the schedule. By using such a relaxed consistency model for the schedule, Tiger achieves scalability and fault tolerance while still providing $e consistent, coordinated service required by viewers.

The integration of virtual memory management and interprocess communication in the Accent network operating system kernel is examined. The design and implementation of the Accent memory management system is discussed and its performance, both on a series of message-oriented benchmarks and in normal operation, is analyzed in detail.