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_setscheduler(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.
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.
Programming for the real world - POSIX.4
by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0
COLOPHON
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
