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;long tv_nsec;};
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 user space.
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. This method of adjusting the quantum was removed starting with Linux 2.6.24.
Linux 3.9 added a new mechanism for adjusting (and
viewing) the SCHED_RR
quantum: the /proc/sys/kernel/sched_rr_timeslice_ms
file exposes the quantum as a millisecond value, whose
default is 100. Writing 0 to this file resets the quantum
to the default value.
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
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Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996 %%%LICENSE_START(GPLv2+_DOC_FULL) 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, see <http://www.gnu.org/licenses/>. %%%LICENSE_END 1996-04-01 Tom Bjorkholm <tombmydata.se> First version written 1996-04-10 Markus Kuhn <mskuhncip.informatik.uni-erlangen.de> revision |