This paper presents the design and implementation of a "quasi real-time" garbage collector for Concurrent Caml Light, an implementation of ML with threads. This two-generation system combines a fast, asynchronous copying collector on the young generation with a nondisruptive concurrent marking collector on the old generation. This design crucially relies on the ML compiletime distinction between mutable and immutable objects. 1 Introduction This paper presents the design and implementation of a garbage collector for Concurrent Caml Light, an implementation of the ML language that provides multiple threads of control executing concurrently in a shared address space. Garbage collection --- the automatic reclamation of unused memory space --- is one of the most problematic components of run-time systems for multi-threaded languages. The naive "stop-the-world" approach, where all threads synchronously stop executing the user's program to perform garbage collection, is clearly inadequate,...

The complexity of systems for automatic control and other safety-critical applications grows rapidly. Computer software represents an increasing part of the complexity. As larger systems are developed, we need to find scalable techniques to manage the complexity in order to guarantee high product quality. Memory management is a key quality factor for these systems. Automatic memory management, or garbage collection, is a technique that significantly reduces the complex problem of correct memory management. The risk of software errors decreases and development time is reduced. Garbage collection techniques suitable for interactive and soft real-time systems exist, but few approaches are suitable for systems with hard real-time requirements, such as control systems (embedded systems). One part of the problem is solved by incremental garbage collection algorithms, which have been presented before. We focus on the scheduling problem which forms the second part of the problem, i.e. how the work of a garbage collector should be scheduled in order

. We present a new algorithm for garbage collection of the term stack in David H. D. Warren's abstract Prolog machine (WAM). The algorithm exploits the possibilities of using a large address space, with special attention paid to virtual memory behaviour. The time required for the algorithm depends linearly on the size of the areas in which garbage is collected. Pseudo-code is given for the whole algorithm. It has been fully implemented in Tricia, a Prolog developed at UPMAIL for the DEC-2060 computer. The research reported herein was supported by the National Swedish Board for Technical Development (STU). 1. PROBLEM In languages with dynamic memory allocation it often happens that an instance of a data structure is not needed for the rest of the computation. Assuming that virtual memory is a limited resource (although it may be very large) it is desirable to be able to re-use such garbage structures. Placing the responsibility of returning garbage on the programmer is a too heavy bu...