Source : Free On-Line Dictionary of Computing

load balancing
     
         Techniques which aim to spread
        tasks among the processors in a {parallel processor} to avoid
        some processors being idle while others have tasks queueing
        for execution.  Load balancing may be performed either by
        heavily loaded processors (with many tasks in their queues)
        sending tasks to other processors; by idle processors
        requesting work from others; by some centralised task
        distribution mechanism; or some combination of these.  Some
        systems allow tasks to be moved after they have started
        executing ("{task migration}") others do not.  It is important
        that the {overhead} of executing the load balancing
        {algorithm} does not contribute significantly to the overall
        processing or communications load.
     
        Distributed scheduling {algorithm}s may be static, dynamic or
        preemptive.  Static algorithms allocate processes to
        processors at run time while taking no account of current
        network load.  Dynamic algorithms are more flexible, though
        more computationally expensive, and give some consideration to
        the network load before allocating the new process to a
        processor.  Preemptive algorithms are more expensive and
        flexible still, and may migrate running processes from one
        host to another if deemed beneficial.  Research to date
        indicates that dynamic algorithms yield significant
        performance benefits, but that further (though lesser) gains
        may be had through the addition of process migration
        facilities.
     
        (1995-03-13)