A Time- and Space-Efficient Garbage Compaction Algorithm

Given an area of storage containing scattered marked nodes, one may wish to rearrange them into a compact mass at one end of the area, meanwhile revising all pointers to marked nodes to show their new locations. An algorithm is here described which accomplishes this task in Iinear time relative to the size of the storage area, and in space of the order of one bit for each pointer. The algorithm operates by reversibly encoding the situation that a collection of locations point to a single location by a linear list, emanating from the pointed-to location, passing through the pointing locations, and terminating with the pointed-to location\u27s transplanted contents

Concurrent Compaction in JVM Garbage Collection

This paper provides a brief overview of both garbage collection (GC) of memory and parallel processing. We then cover how parallel processing applies to GC. Specifically, these concepts are focused within the context of the Java Virtual Machine (JVM). With that foundation, we look at various algorithms that perform compaction of fragmented memory during the GC process. These algorithms are designed to run concurrent to the application running. Such concurrently compacting GC behavior stems from a desire to reduce \stop-the-world pauses of an application

Automated Verification of Practical Garbage Collectors

Garbage collectors are notoriously hard to verify, due to their low-level interaction with the underlying system and the general difficulty in reasoning about reachability in graphs. Several papers have presented verified collectors, but either the proofs were hand-written or the collectors were too simplistic to use on practical applications. In this work, we present two mechanically verified garbage collectors, both practical enough to use for real-world C# benchmarks. The collectors and their associated allocators consist of x86 assembly language instructions and macro instructions, annotated with preconditions, postconditions, invariants, and assertions. We used the Boogie verification generator and the Z3 automated theorem prover to verify this assembly language code mechanically. We provide measurements comparing the performance of the verified collector with that of the standard Bartok collectors on off-the-shelf C# benchmarks, demonstrating their competitiveness