https://bugzilla.kernel.org/show_bug.cgi?id=27052 Summary: man sched_rr_get_interval says the interval depend on nice, but it's incorrect. Product: Documentation Version: unspecified Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: man-pages AssignedTo: documentation_man-pages@xxxxxxxxxxxxxxxxxxxx ReportedBy: kosaki.motohiro@xxxxxxxxxxxxxx Regression: No man sched_rr_get_interval says SCHED_RR quantum depend on nice value. ---------------------------------------------------------------------------------- Linux Notes POSIX does not specify any mechanism for controlling the size of the round-robin time quantum. However, Linux provides a (non-portable) 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. ---------------------------------------------------------------------------------- But current code doesn't depent on it. it always use 0.1 seconds. Hehe, The code comments is misleading too. It's not knob. ;) ---------------------------------------------------------------------------------- /* * These are the 'tuning knobs' of the scheduler: * * default timeslice is 100 msecs (used only for SCHED_RR tasks). * Timeslices get refilled after they expire. */ #define DEF_TIMESLICE (100 * HZ / 1000) (snip) static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued) { update_curr_rt(rq); watchdog(rq, p); /* * RR tasks need a special form of timeslice management. * FIFO tasks have no timeslices. */ if (p->policy != SCHED_RR) return; if (--p->rt.time_slice) return; p->rt.time_slice = DEF_TIMESLICE; /* * Requeue to the end of queue if we are not the only element * on the queue: */ if (p->rt.run_list.prev != p->rt.run_list.next) { requeue_task_rt(rq, p, 0); set_tsk_need_resched(p); } } (snip) static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task) { /* * Time slice is 0 for SCHED_FIFO tasks */ if (task->policy == SCHED_RR) return DEF_TIMESLICE; else return 0; } ---------------------------------------------------------------------------------- I think the man page only describe O(1) scheduler. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
