Jeffrey L. Eppinger

The duality of memory and communication in the implementation of a multiprocessor operating system

Mach is a multiprocessor operating system being implemented at Carnegie-Mellon University. An important component of the Mach design is the use of memory objects which can be managed either by the kernel or by user programs through a message interface. This feature allows applications such as transaction management systems to participate in decisions regarding secondary storage management and page replacement. This paper explores the goals, design and implementation of Mach and its external memory management facility. The relationship between memory and communication in Mach is examined as it relates to overall performance, applicability of Mach to new multiprocessor architectures, and the structure of application programs.

Support for Distributed Transactions in the TABS Prototype

The TABS prototype is an experimental facility that provides operating system-level support for distributed transactions that operate on shared abstract types. The facility is designed to simplify the construction of highly available and reliable distributed applications. This paper describes the TABS system model, the TABS prototypes structure, and certain aspects of its operation. The paper concludes with a discussion of the status of the project and a preliminary evaluation.

An empirical study of insertion and deletion in binary search trees

This paper describes an experiment on the effect of insertions and deletions on the path length of unbalanced binary search trees. Repeatedly inserting and deleting nodes in a random binary tree yields a tree that is no longer random. The expected internal path length differs when different deletion algorithms are used. Previous empirical studies indicated that expected internal path length tends to decrease after repeated insertions and asymmetric deletions. This study shows that performing a larger number of insertions and asymmetric deletions actually increases the expected internal path length, and that for sufficiently large trees, the expected internal path length becomes worse than that of a random tree. With a symmetric deletion algorithm, however, the experiments indicate that performing a large number of insertions and deletions decreases the expected internal path length, and that the expected internal path length remains better than that of a random tree.

High Performance Distributed Transaction Processing in a General Purpose Computing Environment

This paper argues that transaction processing adds relatively little overhead to applications that access shared abstract data objects. It also argues that transaction processing can be made easy to use for both users and implementors of shared objects. The implication is that transaction processing can be a very useful technique in a variety of application domains. To provide more evidence as to the utility of transaction systems, the paper briefly describes the Camelot Distributed Transaction Facility, which has been developed at Carnegie Mellon University. Camelot executes on a variety of uni- and multi-processors on top of the Unix-compatible, Mach operating system. The paper also describes Camelots interfaces and contains preliminary performance information gathered on pre-alpha release versions of Camelot.