The time slice (also called time quantum) for threads with SCHED_RR policy can, according to the sched_rr_get_interval man page be obtained using
int sched_rr_get_interval(pid_t pid, struct timespec *tp); This indicates that there could be different values set for different processes / threads. According to the same man page, however, the value can (since kernel 3.9) be adjusted using /proc/sys/kernel/sched_rr_timeslice_ms, which, however, does not seem to allow to change the configuration per thread in a sensible way.
Other places dealing with real-time scheduling also do not provide information how the time slice for SCHED_RR threads can be set per thread (man chrt, man sched_setattr, SO: How to know linux scheduler time slice?).
It it possible to set the time slice individually per SCHED_RR thread? If so, what is the preferred approach to do so?
