Developing and Porting C and C++ Applications on AIX

8.7. Pthread priority and scheduling

By default, each Pthread within a process has its own a dynamic or floating priority on AIX. This mechanism ensures that all Pthreads on a system have an opportunity to run and not be locked out by other Pthreads. As individual Pthreads consume CPU time, they are charged. Pthreads that are not ready to run, and that are not given a processor upon which they consume cycles, are not charged. Over time, CPU intensive Pthreads use more CPU cycles, are charged more, and their priority degrades. Pthreads that run only briefly before being preempted or relinquishing control of the processor tend to retain a fairly constant priority. The net result is that I/O intensive tasks stay near a constant priority, and computational ...