Generational real-time garbage collection a three-part invention for young objects

While real-time garbage collection is now available in production virtual machines, the lack of generational capability means applications with high allocation rates are subject to reduced throughput and high space overheads. Since frequent allocation is often correlated with a high-level, object-oriented style of programming, this can force builders of real-time systems to compromise on software engineering. We have developed a fully incremental, real-time generational collector based on a tri-partite nursery, which partitions the nursery into regions that are being allocated, collected, and promoted. Nursery collections are incremental, and can occur within any phase of a mature collection. We present the design, mathematical model, and implementation of our collector in IBM's production Real-time Java virtual machine, and show both analytically and experimentally that the collector achieves real-time bounds comparable to a non-generational Metronome-style collector, while cutting memory consumption and total execution times by as much as 44% and 24% respectively.