Setting a Nondegrading Batch Priority

Setting a Nondegrading Batch Priority

Any user can give create a process with a nondegrading priority in the batch range. This is done with the npri command (see the npri(1) reference page).

npri -h 129 echo hello from the Batch queue

The specified command executes with fixed priority 129 (in this example). The same priority change could be performed within the program using schedctl() (see the schedctl(2) reference page), as shown in Example 6-1.

Example 6-1 : Setting a Nondegrading Batch Priority

if (-1 == schedctl(NDPRI,0,129))
   { perror("most unlikely error"); }

The smallest numerical value a regular user can set in these ways is established by the system tuning parameter ndpri_hilim. To see its value use systune, as shown in Example 6-2.

Example 6-2 : Displaying Tuning Variable ndpri_hilim

# systune -i
systune-> ndpri_hilim
          ndpri_hilim = 128 (0x80)

Typically ndpri_hilim is set to 128, the superior priority within the batch range. The system administrator could change the limit to a smaller number, allowing ordinary users to set nondegrading priorities that compete with interactive processes, or even with real-time processes.