Ncr Corporation

Kevin R Brasche

Vernon Keith Boland

Kenneth A Smith

An improved affinity process scheduling method for a multiprocessor computer system, wherein a process previously executed on a processor within the computer system is affined to the processor on which it previously executed, and will be scheduled for execution by the affined processor during subsequent requests for execution of the affined process. The improved affinity process scheduling method monitors the length of time the affined process resides on the system run queue awaiting execution by its affined processor; and schedules the affined process for execution with another available processor when the length of time the affined process has been waiting for execution exceeds a predetermined 'steal-age' threshold. The improved affinity process scheduling method also monitors the processing load borne by the affined processor, determines therefrom a headroom parameter for the affined processor, the headroom parameter indicating the remaining load capacity of the affined processor; and schedules the affined process for execution with another available processor when the headroom of the affined processor is less than a predetermined 'low-headroom' threshold.

Method for load balancing a per processor affinity scheduler wherein

A method for assigning processes to processors within a multi-processor computer system employing a sleep/wakeup facility whereby a first process requiring information from a second process is placed into a 'sleep' state by said computer system until said second process is able to provide said required information, said first process thereupon being awakened by said computer system so that said first process may continue processing with the required information. The method comprising the steps of identifying a pair of processes which frequently exchange wakeup requests, and assigning the processes within the pair of processes to the same processor within the multi-processor computer system for execution. To identify frequently communicating processes, the method of the present invention maintains a record of each 'wakeup' request issued by the computer system, the record including: an identification of the process on whose behalf said wakeup request is issued; and an identification of the process to which said wakeup request is issued. The records are periodically examined to determine a count of the number of wakeup requests between pairs of processors. Should the number of wakeup requests between two processors exceed a predetermined threshold, those two processors are assigned to the same processor within the multi-processor computer system for execution.

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Irmo, SC, United States of America

Kevin R Brasche