Structure Of Operating System Research Articles

Hardware and software support for efficient exception handling

Program-synchronous exceptions, for example, breakpoints, watchpoints, illegal opcodes, and memory access violations, provide information about exceptional conditions, interrupting the program and vectoring to an operating system handler. Over the last decade, however, programs and run-time systems have increasingly employed these mechanisms as a performance optimization to detect normal and expected conditions. Unfortunately, current architecture and operating system structures are designed for exceptional or erroneous conditions, where performance is of secondary importance, rather than normal conditions. Consequently, this has limited the practicality of such hardware-based detection mechanisms. We propose both hardware and software structures that permit efficient handling of synchronous exceptions by user-level code. We demonstrate a software implementation that reduces exception-delivery cost by an order-of-magnitude on current RISC processors, and show the performance benefits of that mechanism for several example applications.

Hardware and software support for efficient exception handling

Program-synchronous exceptions, for example, breakpoints, watchpoints, illegal opcodes, and memory access violations, provide information about exceptional conditions, interrupting the program and vectoring to an operating system handler. Over the last decade, however, programs and run-time systems have increasingly employed these mechanisms as a performance optimization to detect normal and expected conditions. Unfortunately, current architecture and operating system structures are designed for exceptional or erroneous conditions, where performance is of secondary importance, rather than normal conditions. Consequently, this has limited the practicality of such hardware-based detection mechanisms. We propose both hardware and software structures that permit efficient handling of synchronous exceptions by user-level code. We demonstrate a software implementation that reduces exception-delivery cost by an order-of-magnitude on current RISC processors, and show the performance benefits of that mechanism for several example applications.

Design tradeoffs for software-managed TLBs

An increasing number of architectures provide virtual memory support through software-managed TLBs. However, software management can impose considerable penalties that are highly dependent on the operating system's structure and its use of virtual memory. This work explores software-managed TLB design tradeoffs and their interaction with a range of monolithic and microkernel operating systems. Through hardware monitoring and simulation, we explore TLB performance for benchmarks running on a MIPS R2000-based workstation running Ultrix, OSF/1, and three versions of Mach 3.0.

The impact of operating system structure on memory system performance

In this paper we evaluate the memory system behavior of two distinctly different implementations of the UNIX operating system: DEC's Ultrix, a monolithic system, and Mach 3.0 with CMU's UNIX server, a microkernel-based system. In our evaluation we use combined system and user memory reference traces of thirteen industry-standard workloads. We show that the microkernel-based system executes substantially more non-idle system instructions for an equivalent workload than the monolithic system. Furthermore, the average instruction for programs running on Mach has a higher cost, in terms of memory cycles per instruction, than on Ultrix. In the context of our traces, we explore a number of popular assertions about the memory system behavior of modern operating systems, paying special attention to the effect that Mach's microkernel architecture has on system performance. Our results indicate that many, but not all of the assertions are true, and that a few, while true, have only negligible impact on real system performance.

An OS-based reference structure for generic control softwate of FMSs

In the paper, the structure of generic control software of flexible manufacturing systems (FMSs) is considered. By indicating similarities between the control software of FMSs and the operating system (OS) of distributed computer systems, a reference model for generic control software structure of FMSs is proposed based on the software structure of computer operating systems.

Design tradeoffs for software-managed TLBs

An increasing number of architectures provide virtual memory support through software-managed TLBs. However, software management can impose considerable penalties, which are highly dependent on the operating system's structure and its use of virtual memory. This work explores software-managed TLB design tradeoffs and their interaction with a range of operating systems including monolithic and microkernel designs. Through hardware monitoring and simulations, we explore TLB performance for benchmarks running on a MIPS R2000-based workstation running Ultrix, OSF/1, and three versions of mach 3.0. Results: New operating systems are changing the relative frequency of different types of TLB misses, some of which may not be efficiently handled by current architectures. For the same application binaries, total TLB service time varies by as much as an order of magnitude under different operating systems. Reducing the handling cost for kernel TLB misses reduces total TLB service time up to 40%. For TLBs between 32 and 128 slots, each doubling of the TLB size reduces total TLB service time up to 50%.

Modelling operating system structures by timed stream processing functions

AbstractSome extensions of the basic formalism of stream processing functions are useful to specify complex structures such as operating systems. In this paper we give the foundations of higher order stream processing functions. These are functions which send and accept not only messages representing atomic data, but also complex elements such as functions. Some special notations are introduced for the specification and manipulation of such functions. A representation of time is outlined, which enables us to model time dependent behaviour. Finally, we demonstrate how characteristic operating system structures can be modelled by timed higher order stream processing functions.

Multivariable self-tuning power system stabilizer simulation and implementation studies

A multi-input multi-output (MIMO) adaptive power system stabilizer which damps dynamic oscillations is presented. The single-input single-output (SISO) pole-shifting adaptive control algorithm is used as the basis. Its extension to the MIMO controller combines and coordinates the stabilizing contributions from both the excitation and governor systems. The advantage of the adaptive feature is that it can track the operating conditions and system structure changes. The proposed stabilizer can be used with hydro and turbogenerators. Computer simulation results show that the adaptive stabilizer improves the damping of power system oscillations. >

Considerations for applying multiple-level protocols to satellite communication networks

U.S. space system designers are becoming increasingly concerned about the robustness, capacity, and interoperability of future space communications networks and are seeking new approaches. This paper investigates the feasibility of applying a functional analogue of the current International Organization for Standardization's seven-level protocol model for intercomputer communications to space-ground communications links and demonstrates that a mapping into the space environment is possible. For this purpose 1. (1) the functions and interrelationships of the protocol levels are outlined, 2. (2) strong analogies are pointed out between the multilevel protocol organization and the structure of software operating systems, 3. (3) the operations for a typical interchange of a message from terminal-to-satellite followed by a satellite-to-terminal response are described, and 4. (4) the principal concepts and implications for their further development are summarized.

Thermodynamic similarity and prediction of the properties and characteristics of substances and processes

Principles of the theory of thermodynamic similarity are considered in application to all aggregate states of a substance, including phase transitions, and to the change in dissipative structures in open systems.

Filestore structure of a single-user operating system

This paper is a description of a filestore structure of a single-user operating system MICRODOS (see [Ranai, 1, 2]). A hybrid filestore structure of the random page map type (SOLO system see [Hansen, 5]) and the sequential chain linked type (OS6 system see [Stoy and Strachey, 3, 4]) was adopted for MICRODOS system.

A critique of unix

AbstractThe UNIX operating system enjoys an ever increasing popularity throughout the computing community; there will be 1.4 million UNIX licences distributed by 1985, rising at a rate of about 400,000 per annum.With universal acceptance of a system comes a dangerously high degree of inertia. Consider the analogous area of programming languages, where there has been great resistance to change, despite major advancements.This paper presents a critique of UNIX, based on three areas which we consider to be of vital importance to future operating systems. These areas are operating system structures and design, programming support environments and distributed computing.The criticisms presented are in no way intended to discredit UNIX. UNIX compares favourably with most of the present generation of operating systems. The intention is to highlight deficiencies in the state of the art in operating system design.

The Application of Multiprocessors to Scientific Problems: The Potential and the Pitfalls

The objective of research on the MIDAS project is to demonstrate the viability of a multiprocessor approach to computing and to develop a general purpose, extensible architecture which can be used to address the growing computational requirements of the scientific community. To be successful in this endeavor, however, requires more than simply designing, or even constructing, new hardware structures. To achieve high performance on future systems will require software approaches which can exploit parallel architectures as fully as possible. A critical issue, therefore, is to understand the functional requirements of a large class of applications. The requirernents must be critically examined and, in many cases, new approaches to old algorithms investigated. For highly parallel systems to be effectively utilized, they must be flexible and adaptable to specific application requirements. In particular, they will probably need a variety of control and communication mechanisms to facilitate load balancing of a problem and to minimize bottlenecks in performance. The effective utilization of highly parallel architectures, however, raises many new questions. Traditional operating system structures must, for example, be re-examined. Fault-tolerant environments, with error recovery capability, become increasingly important as the number of components and processors increases. Language extensions to support parallel operations are obviously required, and ultimately new languages are needed to explicitly exploit parallel constructs. A new generation of development and debugging tools will be necessary in order to examine programn performance and operation in an asynchronous parallel environment.

Cycle statistics of steady states for master-equation systems

A systematic graph theoretical treatment of steady-state master-equation systems is presented, in order to give a general formulation to Hill’s theory of cycle fluxes which characterizes the cyclic-action structure of open systems in nonequilibrium steady states accompanied by nonzero steady flows of energy or materials between the systems and their environments, such as laser actions or enzymatic reactions. In our formalism, a steady state is described by an ensemble of cycles C’s with each of which a probability current ω(C) and an occurrence probability u(C) are associated. A steady flow is expressed as an average over the cycles with ω(C), i.e., ∑C ω(C) ×(elementary flow generated in C). A similar cycle-average formula by u(C) is also given to state quantities. The Kirchhoff formula for steady states is also referred to.

Security in the Nebula computer architecture

The problem of security in multi-function computer systems arises because the software in such systems is too complex to be proven to be correct. Multilevel secure operating systems attempt to deal with this problem by dividing the applications software into separate "tasks" and controlling the ways in which these tasks interact. While the internal behavior of each task still cannot be guaranteed, the security of the system as a whole can be demonstrated, provided the restrictions on task interaction can be enforced.To control the interaction of tasks, it must be possible to isolate each task from undesired examination or interference by other tasks. This isolation is usually accomplished by providing each untrusted task with its own "virtual" environment. The trusted system software and the hardware are responsible for making sure that an untrusted program cannot operate outside its own environment and that the physical resources allocated to establish the virtual environment do not violate the isolation requirements. Communication between these virtual environments is then controlled by the trusted system software.Ultimately, the realization of such an operating system structure produces a quantity of "trusted system software" that still must be verified to insure the security of the system. To practically realize such a system, careful design of the software and hardware is required to minimize the amount of verified code and isolate it from corruption by the unverified system software.The Nebula computer architecture includes a set of mechanisms that are designed to provide the isolation necessary to establish a secure system. Of more practical importance is the fact that these mechanisms will allow valid operations to be identified with minimal overhead and to proceed with minimal interference. These mechanisms are described below under the general headings of virtual addressing, protection states, secure user I/0 and task execution control.

Artemis—an operating system for OSI microcomputers

The file system and structure of a single-user operating system is described. The system is designed to run in a laboratory setting on a small microcomputer connected to a network with both private and network disk storage.

On the duality of operating system structures

Many operating system designs can be placed into one of two very rough categories, depending upon how they implement and use the notions of process and synchronization. One category, the "Message-oriented System," is characterized by a relatively small, static number of processes with an explicit message system for communicating among them. The other category, the "Procedure-oriented System," is characterized by a large, rapidly changing number of small processes and a process synchronization mechanism based on shared data.In this paper, it is demonstrated that these two categories are duals of each other and that a system which is constructed according to one model has a direct counterpart in the other. The principal conclusion is that neither model is inherently preferable, and the main consideration for choosing between them is the nature of the machine architecture upon which the system is being built, not the application which the system will ultimately support.

Operating system enhancement through firmware

Microprogramming support for the enhancement of operating system design is described in detail, organization structure of realtime operating systems are examined, and criteria proposed for determining which functions are best for firmware implementation. Also, a closed queueing network model with state dependent routing probabilities is developed for studying the impact of microprogramming on a tactical computer system performance. Based on measurement obtained from two applications, the mathematical model is a good approximation in predicting system performance. Avenues for additional research is recommended.

Operating System Structures to Support Security and Reliable Software

Operating System Structures to Support Security and Reliable Software

Decomposition criteria for the design of complex systems

The hierarchical decomposition of a general system is a powerful tool in the reduction of complexity, as has been recognized by various authors. It may be used either to simplify an already existing system, or as an aid to the design of a new system. This paper is concerned with decomposition in the latter sense, being an approach to the modular design of complex systems. The proposed approach involves the estimation of the information transfer between the modules of the system. This necessitates the creation of a multivariate binary probability measure representing the problem, which leads in turn to a general criterion for the decomposition of the system into its most independent subsystems, or modules. As an application, the detection of the modular structure of a computer operating system is discussed.