Research on the Design of Distributed Operating Systems

分布式计算机系统由通过通信网络连接的多个主计算机组成。使分布式计算机系统像集成系统一样运行的操作系统称为分布式操作系统。我们在分布式操作系统上得到了以下结果。分布式操作系统平衡了主机上的负载，从而可以有效地使用主机。我们研究了这种负载均衡的最优策略。首先，我们提出了Tantawi和Towsley单作业类负载均衡算法的改进版本，并将其扩展到多类版本。结果表明，这些算法在计算时间和内存需求方面都比以前的算法有更好的性能。然后分析了系统参数对单作业类最优负载均衡策略的影响，并在多作业类的情况下进行了实验。在这两种情况下，我们都发现了最优负载策略的各种有趣的性质。在此基础上，给出了树形层次网络结构中最优负载均衡的分解算法。我们研究了这一领域的文献，并认识到进程迁移过程中的分页策略和管理分布式共享内存的策略的重要性。设计了一个可用于评估网络寻呼性能的模拟器。我们研究了构成分布式操作系统基础的进程结构。我们进行了“微进程”的概念设计，这些进程主要是在内核外级别实现的。此外，我们在Unix操作系统的内核外级别实现了轻量级进程，评估了它们的性能，并检查了潜在问题。

A distributed computer system consists of a number of host computers connected by a communications network. The operating system which makes a distributed computer system to operate as if it were an integrated system is called a distributed operating system. We obtained the following results on distributed operating systems.1. Distributed operating systems balance the loads on the host computers so that the host computers may be used efficiently. We studied optimal policies for such load balancing. First, we provided an improved version of the Tantawi and Towsley single job class load balancing algorithm, and extended it to a multiclass version. We showed that these proposed algorithms have better performance with respect to the computation time and memory requirements than the previous ones. Then we analyzed the effects of system parameters on the optimal load balancing policies analytically in the case of the single job class and experimentally in the case of the multiple job classes. In both cases, we found various intriguing properties of the optimal load policies. Furthermore, we obtained a decomposition algorithm for optimal load balancing in tree hierarchy network configurations.2. We studied the literature in this field and recognized the importance of page turning policies during process migration and policies for managing distributed shared memory. We designed a simulator that can be used to evaluate the performance of network paging.3. We studied process structuring which forms the basis of distributed operating systems. We performed the conceptual design of "micro-processes" which are implemented mostly in the out-of-kernel level. Furthermore, we implemented light-weight processes in the out-of-kernel level of the UNIX operating systems, evaluated their performance and examined the underlying problems.