MULTIPROCESSOR OPERATING SYSTEM FUNCTIONS AND REQUIREMENTS: A multiprocessor operating system manages all the available resources and schedule functionality to form an abstraction it will facilitates programme execution and interaction with users.
A processor is one of the important and basic types of resources that need to be manage. For effective use of multiprocessors the processor scheduling is necessary.
Processors scheduling undertakes the following tasks:
(i) Allocation of processors among applications in such a manner that will be consistent with system design objectives. It affects the system throughput. Throughput can be improved by co-scheduling several applications together, thus availing fewer processors to each.
(ii) Ensure efficient use of processors allocation to an application. This primarily affects the speedup of the system.
The above two tasks are somehow conflicting each other because maximum speedup needs dedication of a large proportion of a systems processors to a single application which will decrease throughput of the system. Due to the difficulties of automating the process, the need for explicit programmer direction arises to some degree. Generally the language translators and preprocessors provide support for explicit and automatic parallelism.
The two primary facets of OS support for multiprocessing are:
(i) Flexible and efficient interprocess and interprocessor synchronization mechanism, and
(ii) Efficient creation and management of a large number of threads of activity, such as processes or threads.
The latter aspect is important because parallelism is often accomplished by splitting an application into separate, individually executable subtasks that may be allocated to different processors.
The Memory management is the second basic type of resource that needs to be managed. In multiprocessors system memory management is highly dependent on the architecture and inter-connection scheme.
A multiprocessor operating system should provide a hardware independent, unified model of shared memory to facilitate porting of applications between different multiprocessor environments. The designers of the mach operating system exploited the duality of memory management and inter-process communication.
The third basic resource is Device Management but it has received little attention in multiprocessor systems to date, because earlier the main focus point is speedup of compute intensive application, which generally do not generate much input/output after the initial loading. Now, multiprocessors are applied for more balanced general-purpose applications, therefore, the input/output requirement increases in proportion with the realised throughput and speed.
