| A common problem in software engineering is efficiently saving the state of application data structures to non-volatile storage between program executions. If this is accomplished using normal file systems, the programmer is forced to explicitly save the data to files as a stream of uninterpreted bytes, thereby losing both pointer semantics and object identity. A better approach is to use persistent object storage, a natural extension to virtual memory that allows heap data to be saved automatically to disk while maintaining the topology of data structures without any explicit programmer intervention.;If persistent object stores are to replace the functionality of normal file systems, they must be able to address large volumes of data efficiently on standard hardware. High-performance address translation techniques are necessary and important for supporting large address spaces on stock hardware. We present pointer swizzling at page fault time (PS PFT), a coarse-grained address translation scheme suitable for this purpose, and demonstrate it by building a persistent storage system for C++ which we call Texas. We also discuss alternative approaches for portably incorporating fine-grained address translation in Texas for situations where coarse- grained swizzling alone is insufficient. As part of the performance results, we present a detailed analysis of various components of a coarse-grained address translation technique, including a comparison with overall I/O costs.;Pointer swizzling requires run-time knowledge of in-memory object layouts to locate pointers in objects. We have developed and implemented Run-Time Type Description (RTTD) for this purpose; our implementation strategy is portable because it is based on a novel use of compiler-generated debugging information for extracting the necessary type description. RTTD is also useful for other applications such as data structure browsing, and advanced profiling and tracing.;Another part of this research is a study of the interaction between systems similar to PS PFT and operating systems, particularly regarding virtual memory management issues. We suggest areas where operating system implementations can be made more open to improve their performance and extensibility. Finally, we briefly discuss storage management issues, specifically log-structured storage, disk prefetching, and compressed in-memory storage, and provide directions for future research in this area. |
