Multiprocessor Systems

A multiprocessor system is characterized by the presence of many physical processors in the system. There are two approaches to process management in multiprocessor operating system: master-slave configuration an symmetrical multiprocessors.

Master-Slave Configuration

Master-Slave configuration uses centralized process management. One of the processor units is identified as the Master processor. Only the master processor executes the operating system routines and performs all control functions in the system. Thus, the master decides which process is to execute on which processor and for how long. The slave processors simply perform the tasks detailed to them by the master. The advantage of the master-slave configuration is its simplicity. Simplicity results from the fact that all control functions are performed by the master processor. This implies that all signals generated within the operating system should be directed to it. The disadvantages of master-slave configuration are poor reliability and poor scalability.

Centralization of the control function in the master processor leads to poor reliability since failure of the master processor will result in the total failure of the system. Poor scalability results from the fact that the load on the master processor increases as more processors are added to the system. Thus, the master processor may become a bottleneck in efficient utilization of other processors.

Symmetric Multiprocessor

In a symmetric multiprocessor system, processors are identical in their ability to perform control factions. Thus, any processor in the system can perform a control function. In the symmetrical multiprocessor configuration, a hardware processor selection logic is activated whenever an interrupt occurs in the system. This logic determines which processor should handle the interrupt. This arrangement permits a malfunctioning processor to be isolated easily.  The rest of the system can continue its operation, though at a lower level of performance.

      

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