Pointer swizzling at page fault time: efficiently and compatibly supporting huge address spaces on standard hardware

摘要

Pointer swizzling at page fault time is a novel address translation mechanism that exploits conventional address translation hardware. It can support huge address spaces efficiently without long hardware addresses; such large address spaces are attractive for persistent object stores, distributed shared memories, and shared address space operating systems. This swizzling scheme can be used to provide data compatibility across machines with different word sizes, and even to provide binary code compatibility across machines with different hardware address sizes. Pointers are translated ('swizzled') from a long format to a shorter hardware-supported format at page fault time. No extra hardware is required, and no continual software overhead is incurred by presence checks or indirection of pointers. This pagewise technique exploits temporal and spatial locality in much the same way as a normal virtual memory; this gives it many desirable performance characteristics, especially given the trend toward larger main memories. It is easy to implement using common compilers and operating systems.