PThreads Programming by Dick Buttlar

Author:Dick Buttlar [Dick Buttlar, Jacqueline Farrell, and Bradford Nichols]
Language: eng
Format: epub
Tags: COMPUTERS / Programming Languages / JavaScript
ISBN: 9781449364731
Publisher: O'Reilly Media
Published: 2013-01-24T16:00:00+00:00

Scheduling Pthreads

The operating system continuously selects a single thread to run from a systemwide collection of all threads that are not waiting for the completion of an I/O request or are not blocked by some other activity. Many threaded programs have no reason to interfere with the default behavior of the system’s scheduler. Nevertheless, the Pthreads standard defines a thread-scheduling interface that allows programs with real-time tasks to get involved in the process.

Using the Pthreads scheduling feature, you can designate how threads share the available processing power. You may decide that all threads should have equal access to all available CPUs, or you can give some threads preferential treatment. In some applications, it’s beneficial to give those threads that perform important tasks an advantage over those that perform background work. For instance, in a process-control application, a thread that responds to input for special devices could be given priority over a thread that simply maintains the log. Used in conjunction with POSIX real-time extensions, such as memory locking and real-time clocks, the Pthreads scheduling feature lets you create real-time applications in which the threads with important tasks can be guaranteed to complete their tasks in a predictable, finite amount of time.[15]

Note that, even though the Pthreads standard specifies a scheduling interface, it allows vendors to support or not support its programming interface at their option. If your system supports the scheduling programming interface, the compile-time constant _POSIX_THREAD_PRIORITY_SCHEDULING will be TRUE.[16]

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