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SCHED_GET_PRIORITY_MAX

Linux Programmer's Manual (2)
2014-04-28
 

NAME

sched_get_priority_max, sched_get_priority_min - get static priority range  

SYNOPSIS

#include <sched.h>

int sched_get_priority_max(int policy);

int sched_get_priority_min(int policy);  

DESCRIPTION

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, and SCHED_IDLE. 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 value range 1 to 99 for SCHED_FIFO and SCHED_RR and the priority 0 for SCHED_OTHER, SCHED_BATCH, and SCHED_IDLE. 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.1-2001 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>.  

RETURN VALUE

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 appropriately.  

ERRORS

EINVAL
The argument policy does not identify a defined scheduling policy.
 

CONFORMING TO

POSIX.1-2001.  

SEE ALSO

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

COLOPHON

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Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
SEE ALSO
COLOPHON

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Time: 21:42:58 GMT, July 12, 2014