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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, and SCHED_BATCH.
Further details about these policies can be found in sched_setsched
uler(2).
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 and SCHED_BATCH. Schedul‐
ing 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.1-2001 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_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.
ERRORS
EINVAL The parameter policy does not identify a defined scheduling pol‐
icy.
POSIX.1-2001.
sched_getaffinity(2), sched_getparam(2), sched_getscheduler(2),
sched_setaffinity(2), sched_setparam(2), sched_setscheduler(2)
Programming for the real world - POSIX.4 by Bill O. Gallmeister,
O’Reilly & Associates, Inc., ISBN 1-56592-074-0