Recent Advances in Distributed Garbage Collection

1 Why Distributed Garbage Collection Dynamically-allocated memory must eventually be reclaimed. But manual reclamation is error-prone, and if an object is de-allocated prematurely, a program that later follows a pointer to it might behave incorrectly. Instead, garbage collection (GC) automatically reclaims objects that can no longer be reached by any path of pointers. In a distributed system, an object might not only be referenced from one program, but also from other programs and other computers. This makes manual reclamation quite intractable. We consider here the problem of distributed garbage collection (DGC). DGC is particularly important in a large-scale distributed system, since a de-allocation error might cause a completely unrelated program to fail, possibly far away and an arbitrarily long time later. DGC has been a subject of academic research since at least 1977 3]. With the growth of the Internet, DGC is now receiving its share of commercial attention. For instance, both Java RMI 27] and DCOM 22] come with some form of DGC. The next section contains a quick review of DGC techniques; for a more in-depth treatment, we refer to an earlier survey 20]. Then we detail two recent advances in DGC developed in the context of the Broadcast project. The rst Ph.D student at Ecole Polytechnique. Also with INRIA projet PARA.