sched_get_priority_max returns the maximum priority value that can be
used with the scheduling algorithm identified by policy.
sched_get_priority_min returns the minimum priority value that can be
used with the scheduling algorithm identified by policy. Supported
policy values are SCHED_FIFO, SCHED_RR, and
Processes with numerically higher priority values are scheduled before processes
with numerically lower priority values. Thus, the value returned by
sched_get_priority_max will be greater than the value returned by
Linux allows the static priority value range 1 to 99 for SCHED_FIFO and
SCHED_RR and the priority 0 for SCHED_OTHER. Scheduling priority
ranges for the various policies are not alterable.
The range of scheduling priorities may vary on other POSIX systems, thus it is a
good idea for portable applications to use a virtual priority range and map it
to the interval given by sched_get_priority_max and
sched_get_priority_min. POSIX.1b requires a spread of at least 32
between the maximum and the minimum values for SCHED_FIFO and
POSIX systems on which sched_get_priority_max and
sched_get_priority_min are available define
_POSIX_PRIORITY_SCHEDULING in <unistd.h>.