Summary: Online Load Balancing
Yossi Azar 1
Dept. of Computer Science, TelAviv University. ?
Abstract. We survey online load balancing on various models.
General: The machine load balancing problem is defined as follows: There are
n parallel machines and a number of independent tasks (jobs); the tasks arrive
at arbitrary times, where each task has an associated load vector and duration.
A task has to be assigned immediately to exactly one of the machines, thereby
increasing the load on this machine by the amount specified by the corresponding
coordinate of the load vector for the duration of the task. All tasks must be
assigned, i.e., no admission control is allowed. The goal is usually to minimize
the maximumload, but we also consider other goal functions. We mainly consider
nonpreemptive load balancing, but in some cases we may allow preemption i.e.,
reassignments of tasks. All the decisions are made by a centralized controller.
The online load balancing problem naturally arises in many applications
involving allocation of resources. As a simple concrete example, consider the
case where each ``machine'' represents a communication channel with bounded
bandwidth. The problem is to assign each incoming request for bandwidth to
one of the channels. Assigning a request to a certain communication channel