SCHED_GET_PRIORITY_MAX(2) Linux Programmer's Manual SCHED_GET_PRIORITY_MAX(2)
sched_get_priority_max, sched_get_priority_min - get static priority range
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, SCHED_OTHER, SCHED_BATCH, SCHED_IDLE, and SCHED_DEADLINE. Further details about these policies can be found in sched(7).
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 range 1 to 99 for the SCHED_FIFO and SCHED_RR policies, and the priority 0 for the remaining policies. 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 pri- ority range and map it to the interval given by sched_get_prior- ity_max() and sched_get_priority_min POSIX.1 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_prior- ity_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 pol- icy. On error, -1 is returned, and errno is set appropriately.
EINVAL The argument policy does not identify a defined scheduling pol- icy.
sched_getaffinity(2), sched_getparam(2), sched_getscheduler(2), sched_setaffinity(2), sched_setparam(2), sched_setscheduler(2), sched(7)
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Linux 2017-09-15 SCHED_GET_PRIORITY_MAX(2)