[thirdparty/man-pages.git] / man2 / sched_get_priority_max.2

.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
.\"            First version written
.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
.\"            revision
.\"
.TH sched_get_priority_max 2 (date) "Linux man-pages (unreleased)"
.SH NAME
sched_get_priority_max, sched_get_priority_min  \- get static priority range
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <sched.h>
.P
.BI "int sched_get_priority_max(int " policy );
.BI "int sched_get_priority_min(int " policy );
.fi
.SH DESCRIPTION
.BR sched_get_priority_max ()
returns the maximum priority value that can be used with the
scheduling algorithm identified by
.IR policy .
.BR sched_get_priority_min ()
returns the minimum priority value that can be used with the
scheduling algorithm identified by
.IR policy .
Supported
.I policy
values are
.BR SCHED_FIFO ,
.BR SCHED_RR ,
.BR SCHED_OTHER ,
.BR SCHED_BATCH ,
.BR SCHED_IDLE ,
and
.BR SCHED_DEADLINE .
Further details about these policies can be found in
.BR sched (7).
.P
Processes with numerically higher priority values are scheduled before
processes with numerically lower priority values.
Thus, the value
returned by
.BR sched_get_priority_max ()
will be greater than the
value returned by
.BR sched_get_priority_min ().
.P
Linux allows the static priority range 1 to 99 for the
.B SCHED_FIFO
and
.B SCHED_RR
policies, and the priority 0 for the remaining policies.
Scheduling priority ranges for the various policies
are not alterable.
.P
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
.BR sched_get_priority_max ()
and
.BR sched_get_priority_min ()
POSIX.1 requires
.\" POSIX.1-2001, POSIX.1-2008 (XBD 2.8.4)
a spread of at least 32 between the maximum and the minimum values for
.B SCHED_FIFO
and
.BR SCHED_RR .
.P
POSIX systems on which
.BR sched_get_priority_max ()
and
.BR sched_get_priority_min ()
are available define
.B _POSIX_PRIORITY_SCHEDULING
in
.IR <unistd.h> .
.SH RETURN VALUE
On success,
.BR sched_get_priority_max ()
and
.BR sched_get_priority_min ()
return the maximum/minimum priority value for the named scheduling
policy.
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EINVAL
The argument
.I policy
does not identify a defined scheduling policy.
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001.
.SH SEE ALSO
.ad l
.nh
.BR sched_getaffinity (2),
.BR sched_getparam (2),
.BR sched_getscheduler (2),
.BR sched_setaffinity (2),
.BR sched_setparam (2),
.BR sched_setscheduler (2),
.BR sched (7)
Commit	Line	Data
	1	.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
	2	.\"
	3	.\" SPDX-License-Identifier: GPL-2.0-or-later
	4	.\"
	5	.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
	6	.\" First version written
	7	.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
	8	.\" revision
	9	.\"
	10	.TH sched_get_priority_max 2 (date) "Linux man-pages (unreleased)"
	11	.SH NAME
	12	sched_get_priority_max, sched_get_priority_min \- get static priority range
	13	.SH LIBRARY
	14	Standard C library
	15	.RI ( libc ", " \-lc )
	16	.SH SYNOPSIS
	17	.nf
	18	.B #include <sched.h>
	19	.P
	20	.BI "int sched_get_priority_max(int " policy );
	21	.BI "int sched_get_priority_min(int " policy );
	22	.fi
	23	.SH DESCRIPTION
	24	.BR sched_get_priority_max ()
	25	returns the maximum priority value that can be used with the
	26	scheduling algorithm identified by
	27	.IR policy .
	28	.BR sched_get_priority_min ()
	29	returns the minimum priority value that can be used with the
	30	scheduling algorithm identified by
	31	.IR policy .
	32	Supported
	33	.I policy
	34	values are
	35	.BR SCHED_FIFO ,
	36	.BR SCHED_RR ,
	37	.BR SCHED_OTHER ,
	38	.BR SCHED_BATCH ,
	39	.BR SCHED_IDLE ,
	40	and
	41	.BR SCHED_DEADLINE .
	42	Further details about these policies can be found in
	43	.BR sched (7).
	44	.P
	45	Processes with numerically higher priority values are scheduled before
	46	processes with numerically lower priority values.
	47	Thus, the value
	48	returned by
	49	.BR sched_get_priority_max ()
	50	will be greater than the
	51	value returned by
	52	.BR sched_get_priority_min ().
	53	.P
	54	Linux allows the static priority range 1 to 99 for the
	55	.B SCHED_FIFO
	56	and
	57	.B SCHED_RR
	58	policies, and the priority 0 for the remaining policies.
	59	Scheduling priority ranges for the various policies
	60	are not alterable.
	61	.P
	62	The range of scheduling priorities may vary on other POSIX systems,
	63	thus it is a good idea for portable applications to use a virtual
	64	priority range and map it to the interval given by
	65	.BR sched_get_priority_max ()
	66	and
	67	.BR sched_get_priority_min ()
	68	POSIX.1 requires
	69	.\" POSIX.1-2001, POSIX.1-2008 (XBD 2.8.4)
	70	a spread of at least 32 between the maximum and the minimum values for
	71	.B SCHED_FIFO
	72	and
	73	.BR SCHED_RR .
	74	.P
	75	POSIX systems on which
	76	.BR sched_get_priority_max ()
	77	and
	78	.BR sched_get_priority_min ()
	79	are available define
	80	.B _POSIX_PRIORITY_SCHEDULING
	81	in
	82	.IR <unistd.h> .
	83	.SH RETURN VALUE
	84	On success,
	85	.BR sched_get_priority_max ()
	86	and
	87	.BR sched_get_priority_min ()
	88	return the maximum/minimum priority value for the named scheduling
	89	policy.
	90	On error, \-1 is returned, and
	91	.I errno
	92	is set to indicate the error.
	93	.SH ERRORS
	94	.TP
	95	.B EINVAL
	96	The argument
	97	.I policy
	98	does not identify a defined scheduling policy.
	99	.SH STANDARDS
	100	POSIX.1-2008.
	101	.SH HISTORY
	102	POSIX.1-2001.
	103	.SH SEE ALSO
	104	.ad l
	105	.nh
	106	.BR sched_getaffinity (2),
	107	.BR sched_getparam (2),
	108	.BR sched_getscheduler (2),
	109	.BR sched_setaffinity (2),
	110	.BR sched_setparam (2),
	111	.BR sched_setscheduler (2),
	112	.BR sched (7)