Distributed persistent object system with uniform representation of pointers and its garbage collection

In persistent object storage, one of the most influential overheads at application runtime is caused by the conversion of pointers for transparency among variously represented pointers. Existing systems require some representations of pointers, which causes conversion of pointers and runtime overheads, because of the limitation of 32-bit processors' virtual address space, and efficient garbage collection (GC) of distributed persistent objects. In order to remove overheads of pointer conversion, we propose to use an indirect back pointer (IBP) for a distributed persistent object storage on 64-bit processors. IBP is an auxiliary data structure for part-by-part compacting GC. Virtual spaces of 64-bit processors are so large that systems can exploit the linear mapping of the storage and uniform representation of pointers that do not need the conversion of pointers. IBP maintains a list of inter-partition pointers that is sufficient for part-by-part compacting GC. Because IBP is separated from the pointers that are used by applications, IBP and uniform representation of pointers are compatible. In this way, the proposed system achieves compacting GC and no overheads for conversion of pointers at application runtime.