Real-time priority ranges

Priorities are defined in groups, with some groups dedicated to certain kernel functions. For real-time scheduling policies, an integer between 1 (lowest priority) and 99 (highest priority) is used.

The following table describes the priority range, which can be used when setting the scheduling policy of a process.

Table 1. Description of the priority range
Priority Threads Description

1

Low priority kernel threads

This priority is usually reserved for the tasks that need to be just prior to SCHED_OTHER.

2 - 49

Available for use

The range used for typical application priorities.

50

Default hard-IRQ value

51 - 98

High priority threads

Use this range for threads that run periodically and must have quick response times. Do not use this range for CPU-bound threads as you will starve interrupts.

99

Watchdogs and migration

System threads that must run at the highest priority.