sched_rr_get_interval - get the SCHED_RR interval for the named process

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.

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. Linux 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.

Standard C library (libc, -lc)

sched_rr_get_interval - get the SCHED_RR interval for the named process

POSIX systems on which sched_rr_get_interval() is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

On success, sched_rr_get_interval() returns 0. On error, -1 is returned, and errno is set to indicate the error.

timespec(3), sched(7) Linux man-pages 6.9.1 2024-05-02 sched_rr_get_interval(2)

POSIX.1-2008.

Linux 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.