Patent
1996-05-06
1998-10-20
Banankhan, Majid A.
395672, G06F 946
Patent
active
058260811
ABSTRACT:
The present invention provides a process scheduler or dispatcher for a multiprocessor system for real time applications. This embodiment of the present invention proposes a dispatcher model that maintains a dispatch queue for each processor and a separate global dispatch queue for unbound higher priority real time threads. A processor has its own queue and a dispatcher. Each queue has a separate schedule lock associated with it to protect scheduling operations. A processor's dispatcher selects a thread for execution from one of the queues in the system as a candidate thread to execute. When a candidate thread is selected for execution, the processor proceeds to verify against threads in the global real time queue and the processor's own dispatch queue to select a highest priority runnable thread in the system. Thus, the present invention allows the dispatcher to prevent race conditions and minimize lock contention while assuring that high-priority threads are dispatched as quickly as possible. The present invention is implemented by a synchronization between the operations of dispatching a thread and making a thread runnable.
REFERENCES:
patent: 5185861 (1993-02-01), Valencia
patent: 5379428 (1995-01-01), Belo
Khanna, Sandeep, Sebree, Michael, Zolnowsky, John, "Real Time Scheduling in SunOS 5.0," Proceedings of the Winter 1992 USENIX Conference, 1992, pp. 375-390.
D.L. Black: "Scheduling support for Concurrence and Parallelism in the Mach Computer System," Computer, vol. 23, No. 5, May 1990, Los Alamitos, CA, U.S., pp. 35-43.
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"Dispatcher Queue to Provide Processor Affinity in a Multiprocessor," IBM Technical Disclosure Bulletin, vol. 37, No. 2a, Feb. 1994, Armonk, NY, U.S., pp. 573-575.
Banankhan Majid A.
Sun Microsystems Inc.
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