System Class Policies

The system class uses a fixed-priority policy to run kernel processes such as servers, and housekeeping processes such as the page daemon. Their priorities are not dynamically adjusted like timesharing processes. The system class is reserved for use by the kernel, and users may neither add nor remove a process from the system class. Priorities for system-class processes are set up in the kernel code for the kernel processes, and, once established, these priorities do not change. (User processes running in kernel mode are not in the system class.)