Marc A. Auslander

A methodology for the real world

Register allocation may be viewed as a graph coloring problem. Each node in the graph stands for a computed quantity that resides in a machine register, and two nodes are connected by an edge if the quantities interfere with each other, that is, if they are simultaneously live at some point in the object program. This approach, though mentioned in the literature, was never implemented before. Preliminary results of an experimental implementation in a PL/I optimizing compiler suggest that global register allocation approaching that of hand-coded assembly language may be attainable.

K42: building a complete operating system

K42 is one of the few recent research projects that is examining operating system design structure issues in the context of new whole-system design. K42 is open source and was designed from the ground up to perform well and to be scalable, customizable, and maintainable. The project was begun in 1996 by a team at IBM Research. Over the last nine years there has been a development effort on K42 from between six to twenty researchers and developers across IBM, collaborating universities, and national laboratories. K42 supports the Linux API and ABI, and is able to run unmodified Linux applications and libraries. The approach we took in K42 to achieve scalability and customizability has been successful.The project has produced positive research results, has resulted in contributions to Linux and the Xen hypervisor on Power, and continues to be a rich platform for exploring system software technology. Today, K42, is one of the key exploratory platforms in the DOEs FAST-OS program, is being used as a prototyping vehicle in IBMs PERCS project, and is being used by universities and national labs for exploratory research. In this paper, we provide insight into building an entire system by discussing the motivation and history of K42, describing its fundamental technologies, and presenting an overview of the research directions we have been pursuing.

An overview of the PL.8 compiler

The PL.8 compiler accepts multiple source languages and produces high quality object code for several different machines. The strategy used is to first do a simple translation of the source program to a low level intermediate language. Global optimization and register allocation are then used to improve code rather than relying on special case code selection.

Experience distributing objects in an SMMP OS

Designing and implementing system software so that it scales well on shared-memory multiprocessors (SMMPs) has proven to be surprisingly challenging. To improve scalability, most designers to date have focused on concurrency by iteratively eliminating the need for locks and reducing lock contention. However, our experience indicates that locality is just as, if not more, important and that focusing on locality ultimately leads to a more scalable system. In this paper, we describe a methodology and a framework for constructing system software structured for locality, exploiting techniques similar to those used in distributed systems. Specifically, we found two techniques to be effective in improving scalability of SMMP operating systems: (i) an object-oriented structure that minimizes sharing by providing a natural mapping from independent requests to independent code paths and data structures, and (ii) the selective partitioning, distribution, and replication of object implementations in order to improve locality. We describe concrete examples of distributed objects and our experience implementing them. We demonstrate that the distributed implementations improve the scalability of operating-system-intensive parallel workloads.

Experience with K42, an open-source, Linux-compatible, scalable operating-system kernel

K42 is an open-source, Linux-compatible, scalable operating-system kernel that can be used for rapid prototyping of operating-system policies and mechanisms. This paper reviews the structure and design philosophy of K42 and discusses our experiences in developing and using K42 in the open-source environment.

The evolution of the MVS operating system

The mechanization of computer operations and the extension of hardware functions are seen as the basic purposes of an operating system. An operating system must fulfill those purposes while providing stability and continuity to its users. Starting with the data processing environment of twenty-five years ago, this paper describes the forces that led to the development of the OS/360 system design and then traces the evolution which led to todays MVS system.

K42: lessons for the OS community

We started the K42 project more than ten years ago with the ambitious goal of developing an operating system for next-generation hardware that would be widely valued and thus widely used. Based on the premise that current operating systems were not designed to be scalable, customizable, or maintainable, we set forth to rectify that by applying proven techniques from other disciplines to operating systems and by developing additional innovative mechanisms. Now, ten year later, K42 is used by ten or so universities and national labs for research purposes, not ten million information technology departments desiring better everyday computing platforms. As a presentation to the primary operating systems community we provide an examination from two different perspectives as to what went right and what went wrong. First, we concentrate on what technology worked well and why, and what technology failed or caused undue difficulties, and why. Second, based on that experience, we provide our thoughts on the state and direction of the OS community at large. To be clear, this paper is neither a results paper nor an overview paper; we refer to other papers for background material. Rather, it is an exploration by researchers with experience with at least six different previous operating systems of the merit of technologies investigated in K42, and an extrapolation of the implications of that experience to the wider operating system community.

Supporting hot-swappable components for system software

Summary form only given. A hot-swappable component is one that can be replaced with a new or different implementation while the system is running and actively using the component. For example, a component of a TCP/IP protocol stack, when hot-swappable, can be replaced (perhaps to handle new denial-of-service attacks or improve performance), without disturbing existing network connections. The capability to swap components offers a number of potential advantages such as: online upgrades for high availability systems, improved performance due to dynamic adaptability and simplified software structures by allowing distinct policy and implementation options to be implemented in separate components (rather than as a single monolithic component) and dynamically swapped as needed. In order to hot-swap a component, it is necessary to (i) instantiate a replacement component; (ii) establish a quiescent state in which the component is temporarily idle; (iii) transfer state from the old component to the new component; (iv) swap the new component for the old; and (v) deallocate the old component.

Managing programs and libraries in AIX version 3 for RISC System/6000 processors

This paper describes the program and program-library management facility that has been developed for the AIX operating system, Version 3, as implemented for the IBM POWER (performance optimization with enhanced RISC) architecture. It provides run-time loading of libraries, symbol resolution with type checking, and relocation. In addition, the use of the loader to add programs to an already running process or to the kernel is offered. The advantages of these functions and the techniques needed to provide a usable and efficient realization are described. Particular attention is given to the special problems posed by very large programs, and by very small programs which use services from very large libraries.

Functional sturcture of IBM virtual storage operating systems part I: influences of dynamic address translation on operating system technology

Presented are early developments of storage management techniques, particularly those used in OS/360. Innovations introduced by systems that use dynamic address translation are traced. The impact of these techniques on current IBM System/ 370 Operating Systems is described.