2004-11-03 13:51:07 +00:00
|
|
|
.\" Hey Emacs! This file is -*- nroff -*- source.
|
|
|
|
.\"
|
|
|
|
.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
|
|
|
|
.\"
|
|
|
|
.\" This is free documentation; you can redistribute it and/or
|
|
|
|
.\" modify it under the terms of the GNU General Public License as
|
|
|
|
.\" published by the Free Software Foundation; either version 2 of
|
|
|
|
.\" the License, or (at your option) any later version.
|
|
|
|
.\"
|
|
|
|
.\" The GNU General Public License's references to "object code"
|
|
|
|
.\" and "executables" are to be interpreted as the output of any
|
|
|
|
.\" document formatting or typesetting system, including
|
|
|
|
.\" intermediate and printed output.
|
|
|
|
.\"
|
|
|
|
.\" This manual is distributed in the hope that it will be useful,
|
|
|
|
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
|
|
.\" GNU General Public License for more details.
|
|
|
|
.\"
|
|
|
|
.\" You should have received a copy of the GNU General Public
|
|
|
|
.\" License along with this manual; if not, write to the Free
|
|
|
|
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
|
|
|
|
.\" USA.
|
|
|
|
.\"
|
|
|
|
.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
|
|
|
|
.\" First version written
|
|
|
|
.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
|
|
|
|
.\" revision
|
|
|
|
.\"
|
2011-10-16 04:45:57 +00:00
|
|
|
.TH SCHED_RR_GET_INTERVAL 2 2011-10-16 "Linux" "Linux Programmer's Manual"
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH NAME
|
2007-04-05 14:37:59 +00:00
|
|
|
sched_rr_get_interval \- get the SCHED_RR interval for the named process
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH SYNOPSIS
|
|
|
|
.B #include <sched.h>
|
|
|
|
.sp
|
2007-07-16 18:57:34 +00:00
|
|
|
.BI "int sched_rr_get_interval(pid_t " pid ", struct timespec * " tp );
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH DESCRIPTION
|
2005-10-19 06:54:38 +00:00
|
|
|
.BR sched_rr_get_interval ()
|
2011-10-16 04:50:04 +00:00
|
|
|
writes into the
|
|
|
|
.I timespec
|
|
|
|
structure pointed to by
|
|
|
|
.I tp
|
|
|
|
the round-robin time quantum for the process identified by
|
|
|
|
.IR pid .
|
2011-10-16 04:45:57 +00:00
|
|
|
The specified process should be running under the
|
|
|
|
.B SCHED_RR
|
|
|
|
scheduling policy.
|
2007-04-05 12:50:59 +00:00
|
|
|
|
2011-10-16 04:50:04 +00:00
|
|
|
The
|
|
|
|
.I timespec
|
|
|
|
structure has the following form:
|
2007-04-05 12:50:59 +00:00
|
|
|
|
2007-12-19 06:57:44 +00:00
|
|
|
.in +4n
|
2007-04-05 12:50:59 +00:00
|
|
|
.nf
|
|
|
|
struct timespec {
|
|
|
|
time_t tv_sec; /* seconds */
|
|
|
|
long tv_nsec; /* nanoseconds */
|
|
|
|
};
|
|
|
|
.fi
|
2007-04-05 14:37:59 +00:00
|
|
|
.in
|
2007-04-05 12:50:59 +00:00
|
|
|
|
|
|
|
If
|
2011-10-16 04:50:04 +00:00
|
|
|
.I pid
|
|
|
|
is zero, the time quantum for the calling process is written into
|
|
|
|
.IR *tp .
|
2008-04-23 09:10:40 +00:00
|
|
|
.\" FIXME . On Linux, sched_rr_get_interval()
|
|
|
|
.\" returns the timeslice for SCHED_OTHER processes -- this timeslice
|
|
|
|
.\" is influenced by the nice value.
|
|
|
|
.\" For SCHED_FIFO processes, this always returns 0.
|
|
|
|
.\"
|
2007-04-05 14:37:59 +00:00
|
|
|
.\" The round-robin time quantum value is not alterable under Linux
|
|
|
|
.\" 1.3.81.
|
2007-04-12 22:42:49 +00:00
|
|
|
.\"
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH "RETURN VALUE"
|
|
|
|
On success,
|
2005-10-19 06:54:38 +00:00
|
|
|
.BR sched_rr_get_interval ()
|
2004-11-03 13:51:07 +00:00
|
|
|
returns 0.
|
|
|
|
On error, \-1 is returned, and
|
|
|
|
.I errno
|
|
|
|
is set appropriately.
|
|
|
|
.SH ERRORS
|
|
|
|
.TP
|
|
|
|
.B EFAULT
|
|
|
|
Problem with copying information to userspace.
|
|
|
|
.TP
|
|
|
|
.B EINVAL
|
|
|
|
Invalid pid.
|
|
|
|
.TP
|
|
|
|
.B ENOSYS
|
2007-04-05 14:37:59 +00:00
|
|
|
The system call is not yet implemented (only on rather old kernels).
|
2004-11-03 13:51:07 +00:00
|
|
|
.TP
|
|
|
|
.B ESRCH
|
2011-10-16 04:54:16 +00:00
|
|
|
Could not find a process with the ID
|
|
|
|
.IR pid .
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH "CONFORMING TO"
|
2006-08-03 13:57:17 +00:00
|
|
|
POSIX.1-2001.
|
2007-05-18 10:39:45 +00:00
|
|
|
.SH NOTES
|
2011-10-16 04:45:57 +00:00
|
|
|
POSIX systems on which
|
|
|
|
.BR sched_rr_get_interval ()
|
|
|
|
is available define
|
|
|
|
.B _POSIX_PRIORITY_SCHEDULING
|
2011-10-16 04:50:04 +00:00
|
|
|
in
|
|
|
|
.IR <unistd.h> .
|
2007-05-18 10:39:45 +00:00
|
|
|
.SS Linux Notes
|
2007-04-05 14:37:59 +00:00
|
|
|
POSIX does not specify any mechanism for controlling the size of the
|
|
|
|
round-robin time quantum.
|
2011-10-16 05:01:47 +00:00
|
|
|
Older Linux kernels provide a (nonportable) method of doing this.
|
2007-04-05 14:37:59 +00:00
|
|
|
The quantum can be controlled by adjusting the process's nice value (see
|
|
|
|
.BR setpriority (2)).
|
|
|
|
Assigning a negative (i.e., high) nice value results in a longer quantum;
|
|
|
|
assigning a positive (i.e., low) nice value results in a shorter quantum.
|
|
|
|
The default quantum is 0.1 seconds;
|
2007-04-12 22:42:49 +00:00
|
|
|
the degree to which changing the nice value affects the
|
2007-04-05 14:37:59 +00:00
|
|
|
quantum has varied somewhat across kernel versions.
|
2011-10-16 05:01:47 +00:00
|
|
|
Since Linux 2.6.24,
|
|
|
|
.\" commit a4ec24b48ddef1e93f7578be53270f0b95ad666c
|
|
|
|
the
|
|
|
|
.BR SCHED_RR
|
|
|
|
quantum cannot be modified.
|
2007-04-05 14:37:59 +00:00
|
|
|
.\" .SH BUGS
|
2007-06-21 22:55:04 +00:00
|
|
|
.\" As of Linux 1.3.81
|
2007-05-12 12:53:57 +00:00
|
|
|
.\" .BR sched_rr_get_interval ()
|
|
|
|
.\" returns with error
|
2007-04-05 14:37:59 +00:00
|
|
|
.\" ENOSYS, because SCHED_RR has not yet been fully implemented and tested
|
|
|
|
.\" properly.
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH "SEE ALSO"
|
|
|
|
.BR sched_setscheduler (2)
|
|
|
|
has a description of the Linux scheduling scheme.
|
|
|
|
.PP
|
|
|
|
.I Programming for the real world \- POSIX.4
|
|
|
|
by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0
|