SCHED_RR_GET_INTERVAL
NAMESYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON
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 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.
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 user space. | ||
|
EINVAL |
Invalid pid. | ||
|
ENOSYS |
The system call is not yet implemented (only on rather old kernels). | ||
|
ESRCH |
Could not find a process with the ID pid. |
CONFORMING TO
POSIX.1-2001.
NOTES
POSIX systems on which sched_rr_get_interval() is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.
Linux
notes
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.
SEE ALSO
COLOPHON
This page is part of release 3.69 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 http://www.kernel.org/doc/man−pages/.
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