Windows and Linux thread priority equivalence

Question

Windows OS defines the following constants as thread priority:

• THREAD_PRIORITY_IDLE (-15)
• THREAD_PRIORITY_LOWEST (-2)
• THREAD_PRIORITY_BELOW_NORMAL (-1)
• THREAD_PRIORITY_NORMAL (0)
• THREAD_PRIORITY_ABOVE_NORMAL (1)
• THREAD_PRIORITY_HIGHEST (2)
• THREAD_PRIORITY_TIME_CRITICAL (15)

And Linux has sched_get_priority_max() and sched_get_priority_min() to get thread priority range.

Is it possible to have an equivalence between Windows and Linux thread priority values ?

Answer 1

Default Linux priority range is between -20 (highest) and 20 (idle) with step of 1 and default of 0. Negative (raised) priorities are assignable only by superuser. Note Linux never claims -20 to be Realtime/Time Critical, and RTLinux uses a separate methods to achieve Realtime. Also note in Linux Kernel space these priorities have a different range. The -20:20 is a strictly userspace thing.

Answer 2

I use:

  sched_get_priority_max(policy);
  sched_get_priority_min(policy);

to know the priority range.