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 tr...

A distributed object database stores objects persistently at servers. Applications run on client machines, fetching objects into a client-side cache of objects. If fetching and cache management are done in terms of objects, rather than fixed-size units such as pages, three problems must be solved: 1. which objects to prefetch, 2. how to translate, or swizzle, inter-object references when they are fetched from server to client, and 3. which objects to displace from the cache. This thesis reports the results of experiments to test various solutions to these problems. The experiments use the runtime system of the Thor distributed object database and benchmarks adapted from the Wisconsin OO7 benchmark suite. The thesis establishes the following points: 1. For plausible workloads involving some amount of object fetching, the prefetching policy is likely to have more impact on performance than swizzling policy or cache management policy. 2. A simple breadth-first prefetcher can have performa...

Thor is a distributed object-oriented database where objects are stored persistently at highly-available servers called object repositories, or ORs. In a large Thor system, performance tuning and system reconfiguration dictate that objects must be able to migrate among ORs. The paper describes two schemes for object references that support object migration, one using location-independent names and the other, location-dependent names. The paper analyzes the performance of the two schemes and concludes that location-dependent names are the right choice for systems like Thor, where we want fast access to objects that have migrated. Categories and Subject Descriptors: H.2.4 [Database Management]: Systems: Distributed systems; C.2.4 [Computer-Communication networks]: Distributed Systems --- Distributed databases; D.4.7 [Operating Systems]: Organization and Design --- Distributed systems; E.2 [Data Storage Representations]: Linked representations; H.2.2 [Database Management]: Physical Desig...

I argue against trying to solve the problem of clustering objects into disk pages. Instead, I propose that objects be fetched in groups that may be specific to an application or user, and that can be computed at fetch time. I briefly describe crystals, which serve to record such groups statically. Finally, I speculate that object fetching may be particularly relevant for providing services to very small machines with limited memory, such as personal digital assistants. 1

This paper describes the major issues in the design and implementation of orthogonal persistence in IK. A single and uniform programming paradigm is used to manipulate objects in a persistent and distributed environment. Object references can be freely passed during remote invocations or stored persistently. IK supports orthogonal persistence with type inheritance. Objects are stored persistently when reachable from an Eternal Root, regardless of their type. For programmers, objects are created and manipulated uniformly, independently of the time they persist. Persistent objects are dynamically grouped at run-time into clusters to encapsulate fine-grain language level objects into coarser-grain entities. We present a novel approach to integrate object clustering, naming and garbage collection in persistent systems, and present experimental results.

Smalltalk is an object-oriented programming language and highly interactive uniformly object-structured programming environment, originally developed for the Xerox family of personal workstations. The Smalltalk programming environment supports a single user on a single processor in a single object address space. This thesis describes the design and implementation of Distributed Smalltalk. Distributed Smalltalk extends the Smalltalk system to support the interaction of many users on many machines. It provides communication and interaction among geographically remote Smalltalk users, direct access to remote objects, the ability to construct distributed applications in the Smalltalk environment, and a degree of object sharing among users. Applications of Distributed Smalltalk include mail systems, remote computation servers, remote file servers, and collaborative software development. The distributed aspects of the system are largely user transparent and preserve the reactive quality of Smalltalk objects. A system is reactive to the degree that objects in the system can be easily presented for inspection or modification. Smalltalk is highly reactive in that all objects in the system can be so presented. Inheritance is a fundamental property of Smalltalk that allows objects to acquire behavior from other objects. In designing Distributed Smalltalk, we found that the interaction of inheritance and reactiveness was a major source of difficulty and that this interaction had significant impact on the design of a distributed system. Neither inheritance or reactiveness scaled well fro...