Lazy reference counting for the Microgrid

This papers revisits non-deferred reference counting, a common technique to ensure that potentially shared large heap objects can be reused safely when they are both input and output to computations. Traditionally, thread-safe reference counting exploit implicit memory-based communication of counter data and require means to achieve a globally consistent memory state, either using barriers or locks. Acknowledgeing the distributed nature of upcoming many-core chips, we have developed a novel approach that keeps reference counters at single physical locations and ships the counting operations asynchronously to these locations using hardware primitives, rather than implicitely moving the counter data between threads. Compared to previous methods, our approach does not require full cache coherency.