Michal Ostrowski

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.

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.

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.

Specialized execution environments

Virtualization has become popular (again) as a means of consolidating multiple operating systems (OSes) onto a smaller set of hardware resources. The roles of OSes in such environments have changed. Whereas normally an OS provides balance between the demands of application and hardware support, in the world of virtualization it can be beneficial to split these roles. One OS may support a particular application set and use other OSes to interact with physical hardware. The hypervisor, or virtualization layer, provides communication facilities for the inter-OS communication needed to support such a deployment model.