A Hardware Accelerator for Tracing Garbage Collection

Many workloads are written in garbage-collected languages and GC consumes a significant fraction of resources for these workloads. We propose to decrease this overhead by moving GC into a small hardware accelerator that is located close to the memory controller and performs GC more efficiently than a CPU. We first show a general design of such a GC accelerator and describe how it can be integrated into both stop-the-world and pause-free garbage collectors. We then demonstrate an end-to-end RTL prototype, integrated into a RocketChip RISC-V System-on-Chip (SoC) executing full Java benchmarks within JikesRVM running under Linux on FPGAs. Our prototype performs the mark phase of a tracing GC at 4.2 x the performance of an in-order CPU, at just 18.5% the area. By prototyping our design in a real system, we show that our accelerator can be adopted without invasive changes to the SoC, and estimate its performance, area, and energy.