We measure the distribution of lifetimes for UNIX processes and propose a functional form that fits this distribution well. We use this functional form to derive a policy for preemptive migration, and then use a trace-driven simulator to compare our proposed policy with other preemptive migration policies, and with a non-preemptive load balancing strategy. We find that, contrary to previous reports, the performance benefits of preemptive migration are significantly greater than those of non-preemptive migration, even when the memorytransfer cost is high. Using a model of migration costs representative of current systems, we find that preemptive migration reduces the mean delay (queueing and migration) by 35 -- 50%, compared to non-preemptive migration. 1 Introduction Most systems that perform load balancing use remote execution (i.e. non-preemptive migration) based on a priori knowledge of process behavior, often in the form of a list of process names eligible for migration. Althoug...

This report details a survey of systems providing process or object migration. After an introduction to the topic a number of systems are covered in detail. Four chapters deal with systems providing migration over unmodified UNIX, those providing "classical" process migration and containing modified or new kernels, migration over modern microkernel based operating systems and finally those providing more general "object" migration. The coverage of each system contains a general overview, a detailed examination of the migration subsystem and load balancing support, if any. Migration support is sectioned into an overview, an examination of the migration mechanisms, the effects of migration on inter (task) communication, and details of any environment and associated resource transfer. The summary provides comments on the major design issues identified within the report. It notes that solutions running over raw UNIX are the least complete, and that some level of kernel modification is gene...

With the increased interest in network of workstations for parallel and high performance computing it is necessary to reexamine the use of process migration algorithms, to improve the overall utilization of the system, to achieve high performance and to allow flexible use of idle workstations. Currently, almost all programming environments for parallel systems do not use process migration for task assignments. Instead, a static process assignment is used, with sub optimal performance, especially when several users execute multiple processes simultaneously. This paper highlights the advantages of a process migration scheme for better utilizations of the computing resources as well as to gain substantial speedups in the execution of parallel and multi-tasking applications. We executed several CPU and communication bound benchmarks under PVM, a popular programming environment for parallel computing that uses static process assignment. These benchmarks were executed under the MOSIX multicomputer operating system, with and without its preemptive process migration scheme. The results of these benchmarks prove the advantages of using preemptive process migrations. The paper begins with an overview of MOSIX, a multicomputer enhancement of UNIX that supports transparent process migration for load-balancing, and PVM. We then present the performance of the executions of the benchmarks. Our results show that in some cases the improvements in the performance of PVM with the MOSIX process migration can reach tens or even hundreds of percents.

Creating and bootstrapping an operating system is a difficult process. The RHODOS Operating System is no exception and due to its flexible and modular design the booting process has many requirements not found with monolithic operating systems. This report describes the booting requirements of RHODOS, the latest version of Kbuild, the tool used to create the RHODOS boot image, the image produced by Kbuild, the methods used to load and boot the image, and the state of our hardware platform at the time of booting. * This work was partly supported by Australian Research Council under Grant A48831034 and the Deakin University Research Grant 0504054151. Michael J Hobbs: E-Mail - mick@cm.deakin.OZ.AU. Warren Toomey: E-Mail - wkt@cs.adfa.OZ.AU. Greg J. Wickham: E-Mail - gjw@cm.deakin.OZ.AU. RHODOS September 8, 1994 ii CONTENTS 1 Introduction ..............................................................................................................1 2 RHODOS Booting Requirements ........

: RHODOS is a microkernel based Distributed Operating System that was conceived as being the platform upon which theorists could evaluate their policies. However, it is not enough to return whether a particular implementation of a policy works or not. It is also necessary to state how well the policy works. To achieve this it is necessary to build into RHODOS a mechanism which permits the implementors to receive useful feedback as to how the software performs on the target architecture. This report presents a logical design of an active data collection system that will be built into the RHODOS microkernel and kernel servers. Once implemented, it will be possible to provide dynamic feedback as to the overall usefulness, and the effects on performance that specific policies can induce. *. This work was partly supported by the Australian Research Council under Grants A48831034, A49232429 and Deakin University Research Grant 0504054151. i Table of Contents 1 Introduction.................

This technical report details the research into the design of RHODOS' paging mechanism. RHODOS' main design philosophy is both the building of a high performance modern distributed operating system and the comparison and testing of new and competing strategies and theories in distributed operating systems. Due to this design philosophy the paging facility must be flexible. In fact, the paging facility must be capable of supporting process migration and distributed shared memory as well as being able to allow different paging policies to be implemented. This report firstly covers the additions/modifications required to RHODOS' existing space management functions; and secondly, shows how these additions/modifications are utilised in both the policy and mechanism of paging in RHODOS. 1 Introduction When a computer's core memory is (nearly) all used, then no other memory can be allocated to an existing or new process. Virtual memory is a concept to overcome this problem, by taking advant...