Anomalous Relations among Various Performance Objectives

Abstract Distributed computer systems consist of a set of heterogeneous host computers (i.e., nodes) connected by a communication network. A job that arrives at a node may either be processed locally or transferred to another node for remote processing, which we call load balancing. One possible performance objective of load balancing in distributed computer systems is to minimize the overall mean response time. We can characterize analytically the static load balancing policy whereby the mean overall response time is minimized, which we call the overall optimal policy. This policy, however, lacks fairness in the sense that, for example, two jobs arriving at the same node but being forwarded to different nodes may not have the same expected response time. To satisfy fairness among jobs we can consider an individually optimal load balancing policy whereby jobs arriving at the same node have the same (minimum) expected response time regardless of the nodes which process them. Furthermore, we can think of a node optimal load balancing policy whereby the mean response time of jobs arriving at each node is minimum given the decision by the other nodes of which jobs arriving at those nodes are forwarded. We report the existence of some seemingly anomalous phenomena in the mutual relation among the above policies

Dynamic resource allocation scheme for distributed heterogeneous computer systems

This invention relates to a resource allocation in computer systems, and more particularly, to a method and associated apparatus for shortening response time and improving efficiency of a heterogeneous distributed networked computer system by reallocating the jobs queued up for busy nodes to idle, or less-busy nodes. In accordance with the algorithm (SIDA for short), the load-sharing is initiated by the server device in a manner such that extra overhead in not imposed on the system during heavily-loaded conditions. The algorithm employed in the present invention uses a dual-mode, server-initiated approach. Jobs are transferred from heavily burdened nodes (i.e., over a high threshold limit) to low burdened nodes at the initiation of the receiving node when: (1) a job finishes at a node which is burdened below a pre-established threshold level, or (2) a node is idle for a period of time as established by a wakeup timer at the node. The invention uses a combination of the local queue length and the local service rate ratio at each node as the workload indicator