Formal Derivation of Concurrent Garbage Collectors

Concurrent garbage collectors are notoriously difficult to implement correctly. Previous approaches to the issue of producing correct collectors have mainly been based on posit-and-prove verification or on the application of domain-specific templates and transformations. We show how to derive the upper reaches of a family of concurrent garbage collectors by refinement from a formal specification, emphasizing the application of domain-independent design theories and transformations. A key contribution is an extension to the classical lattice-theoretic fixpoint theorems to account for the dynamics of concurrent mutation and collection.Comment: 38 pages, 21 figures. The short version of this paper appeared in the Proceedings of MPC 201

Hierarchical Memory Management for Parallel Programs

International audienceAn important feature of functional programs is that they are parallel by default. Implementing an efficient parallel functional language, however, is a major challenge, in part because the high rate of allocation and freeing associated with functional programs requires an efficient and scalable memory manager. In this paper, we present a technique for parallel memory management for strict functional languages with nested parallelism. At the highest level of abstraction, the approach consists of a technique to organize memory as a hierarchy of heaps, and an algorithm for performing automatic memory reclamation by taking advantage of a disentanglement property of parallel functional programs. More specifically, the idea is to assign to each parallel task its own heap in memory and organize the heaps in a hierarchy/tree that mirrors the hierarchy of tasks. We present a nested-parallel calculus that specifies hierarchical heaps and prove in this calculus a disentanglement property, which prohibits a task from accessing objects allocated by another task that might execute in parallel. Leveraging the disentanglement property, we present a garbage collection technique that can operate on any subtree in the memory hierarchy concurrently as other tasks (and/or other collections) proceed in parallel. We prove the safety of this collector by formalizing it in the context of our parallel calculus. In addition, we describe how the proposed techniques can be implemented on modern shared-memory machines and present a prototype implementation as an extension to MLton, a high-performance compiler for the Standard ML language. Finally, we evaluate the performance of this implementation on a number of parallel benchmarks

Transactional Sapphire: Lessons in High Performance, On-the-fly Garbage Collection

Constructing a high-performance garbage collector is hard. Constructing a fully concurrent 'on-the-fly', compacting collector is much more so. We describe our experience of implementing the Sapphire algorithm as the first on-the-fly, parallel, replication copying, garbage collector for the Jikes RVM Java virtual machine. In part, we explain our innovations such as copying with hardware and software transactions, on-the-fly management of Java's reference types and simple, yet correct, lock-free management of volatile fields in a replicating collector. We fully evaluate, for the first time, and using realistic benchmarks, Sapphire's performance and suitability as a low latency collector. An important contribution of this work is a detailed description of our experience of building an on-the-fly copying collector for a complete JVM with some assurance that it is correct. A key aspect of this is model checking of critical components of this complicated and highly concurrent system

Actes de la conférence JFLA 2009 (Vingtièmes Journées Francophones des Langages Applicatifs)

Ce fichier regroupe en un seul document l'ensemble des articles acceptés pour la conférence JFLA 2009.Pour la vingtième année consécutive, les Journées Francophones des Langages Applications sont l'occasion de se retrouver dans un cadre agréable et propice aux échanges conviviaux. Cette année, c'est à Saint-Quentin sur Isère, près de Grenoble, que nous nous réunissons, maintenant la tradition de l'alternance mer-montagne. Les neuf articles choisis par le comité de programme reflètent bien la diversité de notre communauté et les avancés tant du point de vue de l'application de langages fonctionnels que de la conception et de l'utilisation d'assistants à la preuve. Nous avons souhaité également inclure des articles plus proches de tutoriels ou de retours d'expérience, ceux-ci étant particulièrement adaptés au cadre pédagogique des Journées. Deux orateurs nous ont fait l'honneur d'accepter notre invitation. L'exposé de Vincent Balat, de l'université Paris 7, intitulé ≪ Ocsigen : approche fonctionnelle typée de la programmation Web ≫ illustre l'utilisation croissante de langages applicatifs dans des milieux inattendus. L'exposé de Bruno Barras, de Trusted Labs, intitulé ≪ Faut-il avoir peur de sa carte SIM ? ≫ présente l'application d'assistants à la preuve dans la modélisation de cartes à puces. Pour la quatrième année consécutive, deux sessions d'une demi-journée chacune sont consacrées à des cours. Le premier porte sur la modélisation de la linguistique (par Gérard Huet, de l'INRIA Paris - Rocquencourt) et le deuxième sur les bibliothèques Coq utilisées dans la preuve récente du théorème des quatre couleurs (par Assia Mahboubi, de l'INRIA Saclay - Île-de-France)

The design and application of an extensible operating system

Tanenbaum, A.S. [Promotor