mirror of https://github.com/mkerrisk/man-pages
127 lines
3.5 KiB
Groff
127 lines
3.5 KiB
Groff
.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
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.\" First version written
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.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
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.\" revision
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.\"
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.TH SCHED_GET_PRIORITY_MAX 2 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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sched_get_priority_max, sched_get_priority_min \- get static priority range
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.SH SYNOPSIS
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.nf
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.B #include <sched.h>
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.PP
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.BI "int sched_get_priority_max(int " policy );
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.BI "int sched_get_priority_min(int " policy );
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.fi
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.SH DESCRIPTION
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.BR sched_get_priority_max ()
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returns the maximum priority value that can be used with the
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scheduling algorithm identified by
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.IR policy .
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.BR sched_get_priority_min ()
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returns the minimum priority value that can be used with the
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scheduling algorithm identified by
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.IR policy .
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Supported
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.I policy
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values are
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.BR SCHED_FIFO ,
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.BR SCHED_RR ,
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.BR SCHED_OTHER ,
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.BR SCHED_BATCH ,
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.BR SCHED_IDLE ,
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and
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.BR SCHED_DEADLINE .
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Further details about these policies can be found in
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.BR sched (7).
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.PP
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Processes with numerically higher priority values are scheduled before
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processes with numerically lower priority values.
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Thus, the value
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returned by
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.BR sched_get_priority_max ()
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will be greater than the
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value returned by
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.BR sched_get_priority_min ().
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.PP
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Linux allows the static priority range 1 to 99 for the
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.B SCHED_FIFO
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and
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.B SCHED_RR
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policies, and the priority 0 for the remaining policies.
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Scheduling priority ranges for the various policies
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are not alterable.
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.PP
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The range of scheduling priorities may vary on other POSIX systems,
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thus it is a good idea for portable applications to use a virtual
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priority range and map it to the interval given by
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.BR sched_get_priority_max ()
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and
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.BR sched_get_priority_min
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POSIX.1 requires
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.\" POSIX.1-2001, POSIX.1-2008 (XBD 2.8.4)
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a spread of at least 32 between the maximum and the minimum values for
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.B SCHED_FIFO
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and
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.BR SCHED_RR .
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.PP
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POSIX systems on which
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.BR sched_get_priority_max ()
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and
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.BR sched_get_priority_min ()
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are available define
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.B _POSIX_PRIORITY_SCHEDULING
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in
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.IR <unistd.h> .
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.SH RETURN VALUE
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On success,
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.BR sched_get_priority_max ()
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and
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.BR sched_get_priority_min ()
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return the maximum/minimum priority value for the named scheduling
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policy.
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On error, \-1 is returned, and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EINVAL
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The argument
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.I policy
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does not identify a defined scheduling policy.
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008.
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.SH SEE ALSO
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.ad l
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.nh
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.BR sched_getaffinity (2),
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.BR sched_getparam (2),
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.BR sched_getscheduler (2),
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.BR sched_setaffinity (2),
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.BR sched_setparam (2),
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.BR sched_setscheduler (2),
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.BR sched (7)
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