sched_rr_get_interval — get the SCHED_RR interval for the named process
#include <sched.h>
int
sched_rr_get_interval( |
pid_t pid, |
struct timespec * tp) ; |
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 specified process
should be running under the SCHED_RR
scheduling policy.
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
.
On success, sched_rr_get_interval
() returns 0. On
error, −1 is returned, and errno
is set appropriately.
Problem with copying information to userspace.
Invalid pid.
The system call is not yet implemented (only on rather old kernels).
Could not find a process with the ID pid
.
POSIX systems on which sched_rr_get_interval
() is available define
_POSIX_PRIORITY_SCHEDULING
in
<
unistd.h
>
POSIX does not specify any mechanism for controlling the
size of the round-robin time quantum. Older Linux kernels
provide 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. Since Linux 2.6.24, the SCHED_RR
quantum cannot be modified.
sched_setscheduler(2) has a description of the Linux scheduling scheme.
Programming for the real world − POSIX.4 by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0
This page is part of release 3.41 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 |