sched_rr_get_interval(2) — Linux manual pages

sched_rr_get_interval
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Name

sched_rr_get_interval — get the SCHED_RR interval for the named process

Synopsis

#include <sched.h>

`int sched_rr_get_interval(`	pid_t	`pid`,
	struct timespec *	`tp)`;

DESCRIPTION

sched_rr_get_interval() writes into the timespec structure pointed to by tp the round-robin time quantum for the process identified by pid.

The timespec structure has the following form:

struct timespec {

time_t tv_sec;
/* seconds */

long tv_nsec;
/* nanoseconds */

};

If pid is zero, the time quantum for the calling process is written into *tp. The identified process should be running under the SCHED_RR scheduling policy.

POSIX systems on which sched_rr_get_interval() is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>

RETURN VALUE

On success, sched_rr_get_interval() returns 0. On error, −1 is returned, and errno is set appropriately.

ERRORS

EFAULT: Problem with copying information to userspace.
EINVAL: Invalid pid.
ENOSYS: The system call is not yet implemented (only on rather old kernels).
ESRCH: The process whose ID is pid could not be found.

CONFORMING TO

POSIX.1-2001.

NOTES

Linux Notes

POSIX does not specify any mechanism for controlling the size of the round-robin time quantum. However, Linux provides a (non-portable) method of doing this. The quantum can be controlled by adjusting the process's nice value (see 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; the degree to which changing the nice value affects the quantum has varied somewhat across kernel versions.

COLOPHON

This page is part of release 2.79 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/.

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 <tombmydata.se>
           First version written
1996-04-10 Markus Kuhn <mskuhncip.informatik.uni-erlangen.de>
           revision

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struct	timespec {
	time_t	`tv_sec`;	/* seconds */
	long	`tv_nsec`;	/* nanoseconds */
};