Windows® via C/C++, Fifth Edition

Thread Priorities

At the beginning of this chapter, I explained how a CPU can run a thread for only about 20 milliseconds before the scheduler assigns another schedulable thread to that CPU. This happens if all the threads have the same priority, but in reality threads are assigned a lot of different priorities and this affects which thread the scheduler picks as the next thread to run.

Every thread is assigned a priority number ranging from 0 (the lowest) to 31 (the highest). When the system decides which thread to assign to a CPU, it examines the priority 31 threads first and schedules them in a round-robin fashion. If a priority 31 thread is schedulable, it is assigned to a CPU. At the end of this thread’s time slice, the system checks to see ...