Hermann Schmutz

Generic Support for Distributed Processing in Heterogeneous Networks

The apparent complexity of distributed application development, especially in a heterogeneous environment, is the prime motivation for the network operating system kernel described in this paper. The kernel reduces this complexity by separating the distribution related issues from the application related ones. It provides an interface of generic objects and operations, which are able to take away from the application programmer most of the problems of distribution, access protection, resource management, and data representation. This paper develops the basic concepts of the kernel from rather general design objectives and illustrates its use and major properties. A prototype implementation, which is running on three different architectures, demonstrates the feasibility of adding these facilities to a given operating system without affecting existing interfaces or applications. The paper reports about early experience with the implementation and performance of the prototype.

An architecture for the cooperation of heterogeneous operating systems

The DAC Network Operating System (DACNOS) was designed to support resource sharing in a world of interconnected heterogeneous computing systems. The prototype implementation demonstrates that it is feasible to add powerful and flexible means for distributed cooperation to an operating system without affecting its existing individual interfaces and applications. The authors describe the important design issues of DACNOS and their experiences with the implementation and performance of a prototype. Particular emphasis is put on the portability of the NOS software and on the design of the interface to the NOS kernel that provides the facilities for distributed cooperation. It is shown by an example how this set of facilities eases the implementation of distributed applications by taking most of the burden of distribution, access protection, resource management and data representation away from the programmer.<<ETX>>

Data Base Research: A Survey

The research activities in the area of data base systems are reviewed. Most of the issues considered by research institutes center around models of information, interactive data manipulation, system aspects, implementation techniques and modelling and analysis. Comparison with industry activities and documented user requirements shows differences of emphasis between research and development. Conclusions are drawn with respect to established and potentially emerging principles in the area of data base design and architecture and with respect to potential future trends in data base research.

Network Operating System Kernels for Heterogenous Environments

A major function of a Network Operating System Kernel is to free application program developers from the need for designing complex protocols. The Operating System analogy for networks offers a paradigm for inter-program cooperation, as if this cooperation were local. Instead of forcing programs to send and interpret messages explicitly, the Network Operating System provides services for remote operations on accustomed data structures, whereby the message exchange as such remains invisible to the programmer.

Performance analysis of suspend locks in operating systems

Performance models of suspend locks in operating systems are developed and analyzed. Analytical expressions and algorithms for numerical results have been obtained for an arbitrary number of processors, an arbitrary number of tasks, and one suspend lock. The results are discussed and important dependencies among the major characteristic quantities such as queue length, processor speed, number of processors, dispatching overhead, and processor degradation are shown. Expressions are derived permitting the control program designer to estimate the system impact of locking during the early design phase.

Autonomous Heterogeneous Computing - Some Open Problems

The integration of heterogeneous operating systems is, in practice, at best at its very beginning and still far from being materialized in its full potential. The subject involves a wide spectrum of issues, including those related to the semantics of functions, to security and to system management. In this paper we will identify some missing functions in each of these areas to prove that there is a significant demand for research, standardization and software extensions.

Experiences with a Portable Network Operating System

DACNOS (Distributed Academic Computing Network Operating System) is a prototype network operating system that facilitates cooperation in heterogeneous multi-vendor computing environments. It is an add-on software system that does not replace nor interfere with the existing host operating system, but enables resource sharing with integrated access control and resource management across the network of heterogeneous computers. We describe the DACNOS design goals and the resulting architecture. Our main focus is on our experiences with the development and use of the prototype. In particular we comment on the portability of the system and the experience with newly written applications. It has been shown that DACNOS is a powerful and convenient application enabling platform for distributed computing in heterogeneous environments.

Remote File Access

This report describes the Remote File Access (RFA) component of the network operating system, which is being implemented in the joint project “Distributed Academic Computing” (DAC) of the University of Karlsruhe and IBM’s European Networking Center at Heidelberg. The DAC project and the RFA component put major emphasis on the bridging of the boundaries of heterogeneity and of remoteness transparent to the user. Accordingly, this report investigates common concepts of the file systems of VM/CMS, VAX VMS, PC DOS and Unix.

An Adaptive Working Set Algorithm

Since the late sixties many publications on paging and related topics have been published dealing with theoretical and practical page replacement algorithms (see references in [1]). If we consider the algorithms based on the LRU (least recently used) principle there are two basic approaches for solving the page replacement problem in a multiprogramming environment: Global (e. g. global LRU) and local (e. g. WS [1] and PFF [13]). The “global LRU” type of algorithms will select for replacement the system wide least recently used pages. This approach is used by many available Operating Systems. It shows satisfactory behavior over most workloads as long as the load on main storage is not too high. The main problem with this approach is the use of “real age” (i. e., the elapsed real time since the page was last referenced) as the basis of page replacement. The real age is, as discussed in section 2, inherently unstable for many programs operating at optimal memory allocation. Global LRU is therefore, in general, not optimal. Available Operating Systems offer additional support to help the user protect critical applications from loosing their pages [2,3].

Virtual machine dispatching under fairness constraints

The paper analyzes the problems of low level dispatching under predictability constraints, with good responsiveness and low overhead. It is shown that nonpreemptive and/or round-robin disciplines fail for the general case. A novel algorithm is proposed based on sorting at time slice intervals. Simulation results are used to discuss the properties of the new dispatching algorithm.