 | | The discussion of scheduling scope is complicated when multiprocessing systems are involved. Many operating systems allow collections of CPUs to be treated as separate units for scheduling purposes. In Digital UNIX, for example, such a grouping is called a processor set and can be created by system calls or administrative commands. The Pthreads standard does recognize that such groupings may exist and refers to them as scheduling allocation domains. However, to avoid forcing all vendors to implement specific allocation domain sizes, the standard leaves all policies and interfaces relating to them undefined. As a result, there's a wide range of standard-compliant implementations out there. Some vendors, such as Digital, provide rich functionality, and others provide very little, even placing all CPUs in a single allocation domain. | |
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