Messages in this thread | | | Subject | Re: [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick | From | Lin Ming <> | Date | Fri, 29 Jul 2011 16:44:03 +0800 |
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On Fri, 2011-07-29 at 16:20 +0800, Peter Zijlstra wrote: > On Fri, 2011-07-29 at 16:18 +0800, Yong Zhang wrote: > > > Nah, if there is 1 runnable task it will always run, preemption simply > > > doesn't matter. There's nothing to preempt it with. > > > > Hmmm, so the newly waked task could be scheduled a little later. > > That means schedule tick judge everything. > > Oh, are you referring to the case where a task gets woken on an idle > remote cpu?
Yong means the case below. At (n tick) there is only 1 task, then another task is woken before (n+1) tick.
On Fri, 2011-07-29 at 15:46 +0800, Yong Zhang wrote: > > Just set_tsk_need_resched(p) if p's slice is over, thus: > > (n tick) ---> (n+1 tick) > set_tsk_need_resched(p); > another task Q is awaked > > If we don't have !sched_feat(WAKEUP_PREEMPT), Q maybe will wait > for tick coming to get scheduled. If we have > !sched_feat(WAKEUP_PREEMPT), Q will get scheduled when some event > happen, like IRQ.
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