2016-09-20 2:08 GMT+08:00 Joonwoo Park <joonw...@codeaurora.org>: > On Sun, Sep 18, 2016 at 07:28:32AM +0800, Wanpeng Li wrote: >> 2016-09-17 9:28 GMT+08:00 Joonwoo Park <joonw...@codeaurora.org>: >> > From: Srivatsa Vaddagiri <va...@codeaurora.org> >> > >> > SCHED_HRTICK feature is useful to preempt SCHED_FAIR tasks on-the-dot >> > (just when they would have exceeded their ideal_runtime). It makes use >> > of a per-cpu hrtimer resource and hence alarming that hrtimer should >> > be based on total SCHED_FAIR tasks a cpu has across its various cfs_rqs, >> > rather than being based on number of tasks in a particular cfs_rq (as >> > implemented currently). As a result, with current code, its possible for >> > a running task (which is the sole task in its cfs_rq) to be preempted >> >> not be preempted much, right? > > I don't think so.... > By saying 'to be preempted much after its ideal_runtime has elapsed' I > wanted to describe the current suboptimal behaviour.
I also described the current suboptimal behaviour. A running task (which is the sole task in its cfs_rq) as the test case 2 you mentioned in another reply is preempted after 10ms since the scheduler tick, however, it will be preempted after 1.5ms since the hrtick fire in test case 1. That's what I mean "not be preempted much for test case 2". Regards, Wanpeng Li
