Where Does The OS Run?

• Master/slave Assignment: Kernel functions always run on a particular processor. Other processors execute user processes.
• Advantage: Resource conflict resolution simplified since single processor has control.
• Single point of failure (Master).
• Peer Assignment: OS executes on all processors. Each processor does its own scheduling from the pool of available processes. Most OSes implement this in an SMP environment.

Mapping Processes to Processors

• Largely an application issue.
• Applications may be written for a particular configuration of the machine.
• Application create threads of computations and channel of communication between these threads assuming a particular machine configuration.
• Applications may be generic in nature
• Create n threads of computations. These threads can execute on machines with 1, <n, n or >n processors.
• OS may assign any number of processors (1 to n) to this application.