Dispatch Parameters

Dispatch Parameters

One of the most important functions of the kernel is ''dispatching'' processes. When a user issues a command and a process is created, the kernel endows the process with certain characteristics. For example, the kernel gives the process a priority for receiving CPU time. This priority can be changed by the user who requested the process or by the Superuser. Also, the length of time (slice-size) that a process receives in the CPU is adjustable by a dispatch parameter. The Periodic Deadline Scheduler (PDS) is also part of the dispatch group. The deadline scheduler is invoked via the schedctl(2) system call in a user program and requires the inclusion of <sys/schedctl.h>. The following parameters are included in the dispatch group:

ndpri_hilim - sets the highest non-degrading priority a user process may have.
ndpri_lolim - sets the lowest non-degrading priority a user process may have.
runq_dl_refframe - sets a limit on the amount of the reference frame that can be allocated.
runq_dl_nonpriv - controls the amount of the reference frame that can be allocated by non-privileged user processes.
runq_dl_use - specifies the longest interval that a deadline process may request.
slice_size - specifies the amount of time a process receives at the CPU.

ndpri_hilim
ndpri_lolim
runq_dl_maxuse
runq_dl_nonpriv
runq_dl_refframe
slice_size