sched_rr_get_interval - get the SCHED_RR interval for the named process
Standard C library (libc, -lc)
#include <sched.h>
int sched_rr_get_interval(pid_t pid, struct timespec *tp);sched_rr_get_interval() writes into the
timespec(3) 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.
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 to indicate the
error.
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.
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.
POSIX.1-2008.
POSIX.1-2001.
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.
POSIX systems on which sched_rr_get_interval() is
available define _POSIX_PRIORITY_SCHEDULING in
<unistd.h>.