GET_PRIORITY_MAX

sched_get_priority_max, sched_get_priority_min ? get static priority range

#include <sched.h>

int sched_get_priority_max(int policy);

int sched_get_priority_min(int policy);

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 SCHED_OTHER.

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 sched_get_priority_min.

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 SCHED_RR.

POSIX systems on which sched_get_priority_max and sched_get_priority_min are available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

On success, sched_get_priority_max and sched_get_priority_min return the maximum/minimum priority value for the named scheduling policy. On error, ?1 is returned, errno is set appropriately.

EINVAL

The parameter policy does not identify a defined scheduling policy.

POSIX.1b (formerly POSIX.4)

sched_setscheduler(2), sched_getscheduler(2), sched_setparam(2), sched_getparam(2).

sched_setscheduler(2) has a description of the Linux scheduling scheme.

Programming for the real world ? POSIX.4 by Bill O. Gallmeister, O’Reilly & Associates, Inc., ISBN 1-56592-074-0
IEEE Std 1003.1b-1993 (POSIX.1b standard)
ISO/IEC 9945-1:1996