This paper examines the implementation of persistent systems on traditional operating systems and on operating systems that directly support persistence, and looks at current attempts to provide flexible architectures that permit persistence to be provided efficiently above the operating system.

Monolithic- and micro-kernel-based operating systems such as Unix have failed to provide application developers with sufficient flexibility. They provide a host of inefficient and often inappropriate abstractions that prevent applications from accessing the hardware to exploit efficiency gains. These problems motivated the Grasshopper project to build a new operating system designed to explicitly support orthogonal persistence. Five years on, Grasshopper has demonstrated the feasibility of such an operating system although several problems have been identified. In light of this, we decided to redesign our kernel using modern techniques. This paper examines the trends in operating system design over the last few years and describes our plans to produce a new persistent micro-kernel.

This paper is concerned with the thread-related interface primitives. These deal with thread context

Support for evolution can be classified as static or dynamic. Static evolvability is principally concerned with structuring systems as separated abstractions. Dynamic evolvability is concerned with the means by which change is effected. Dynamic evolution provides the requisite flexibility for application evolution, however, the dynamic approach is not scalable in the absence of static measures to achieve separation of abstractions. This separation comes at a price in that issues of concern become trapped within static abstraction boundaries, thereby inhibiting dynamic evolution. The need for a unified approach has long been recognised but existing systems that attempt to address this need do so in an ad-hoc manner. The principal reason for this is that these approaches fail to resolve the incongruence in the underlying models. Our contention is that this disparity is incidental rather than fundamental to the problem. To this end we propose an alternative model based on the Compliant Systems Architecture (CSA), a structuring methodology for constructing software systems. The overriding benefit of this work is increased flexibility. Specifically our contribution is an instantiation of the CSA that supports unified static and dynamic evolution techniques. Our model is explored through a worked example in which we evolve an application’s concurrency model. 1

9 Acknowledgements 11 Dedication 12 Definition of Terms 13 1 Introduction 14 1.1 Persistent Store Resource Management : : : : : : : : : : : : : : : 15 1.2 Trends in Operating System Design : : : : : : : : : : : : : : : : : 16 1.3 Arena Design Principles : : : : : : : : : : : : : : : : : : : : : : : 18 1.4 Objectives : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 19 1.5 Summary : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 20 1.6 Structure Of This Thesis : : : : : : : : : : : : : : : : : : : : : : : 20 2 Persistent Store Design 21 2.1 Classification of Persistent Stores : : : : : : : : : : : : : : : : : : 21 2.1.1 Scientific Store : : : : : : : : : : : : : : : : : : : : : : : : 22 2.1.2 Transaction System Store : : : : : : : : : : : : : : : : : : 22 2.1.3 Office/Engineering Store : : : : : : : : : : : : : : : : : : : 23 2.2 Physical Disk Design : : : : : : : : : : : : : : : : : : : : : : : : : 24 2.3 The I/O Bottle Neck : : : : : : : : : : : : : : : : ...