priority

QNX SDP8.0PLMS User's GuideAPIConfigurationDeveloper

The priority statement specifies the scheduling priority and policy for the spawned process.

Format

priority = "policy:priority[:parameters]"

Description

The priority keyword indicates the priority level and scheduling policy to assign to the process (e.g., r:10). The policy parameters include:

  • f - SCHED_FIFO (FIFO scheduling)
  • r - SCHED_RR (Round-robin scheduling)
  • s - SCHED_SPORADIC (Sporadic scheduling). The parameters are applicable only for SCHED_SPORADIC. For example, 
    s:priority:Initial_budget:Low_priority: \ 
                            Replenishment_period:Max_pending_replenishments

Examples

priority = "r:10"

Default

The default value is r:10.

Multiplicity

Zero or one instance in a task block.

Constraints

  • The valid priority values are:
    • 1-255 for QOS 2.2.x.
    • 1-253 for SDP 8.x.
  • If invalid values are specified for priority and policy, the parser will reject the configuration file.
  • If priority is specified in a task, then the task must have one of the exec*() functions so that the priority is used at run time.
  • For sporadic scheduling:
    • The range for priority is:
      • 2-255 for QOS 2.2.x
      • 2-253 for SDP 8.x

    • The range for low_priority is

      • 1-254 for QOS 2.2.x
      • 1-252 for SDP 8.x
    • The priority must always be higher than low_priority.
    • The Max_pending_replenishments can be 1 through SS_REPL_MAX(65535).
    • The init_budget must be smaller than Replenishment_period.
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