sched_rr_get_interval(2) — Linux manual pages

Linux manual pages	Section 2

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 (nonportable) 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 3.33 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/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
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You should have received a copy of the GNU General Public
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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

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