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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
SCHED_RR_GET_INTERVAL(2) Linux Programmer's Manual SCHED_RR_GET_INTERVAL(2)
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.
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.
POSIX.1-2001, POSIX.1-2008.
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.
sched(7)
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latest version of this page, can be found at
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Linux 2017-09-15 SCHED_RR_GET_INTERVAL(2)
Pages that refer to this page: sched_getattr(2) , sched_getscheduler(2) , sched_setattr(2) , sched_setscheduler(2) , syscalls(2) , proc(5) , procfs(5) , sched(7)
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