Manpages - sched_get_priority_max.2

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, 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 priority range and map it to the interval given by sched_get_priority_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_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, and errno is set to indicate the error.

EINVAL

The argument policy does not identify a defined scheduling policy.

POSIX.1-2001, POSIX.1-2008.

*sched_getaffinity*(2), *sched_getparam*(2), *sched_getscheduler*(2), *sched_setaffinity*(2), *sched_setparam*(2), *sched_setscheduler*(2), *sched*(7)

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