Messages in this thread | | | Subject | Re: [PATCH] sched/fair: reduce preemption with IDLE tasks runable(Internet mail) | From | Dietmar Eggemann <> | Date | Wed, 19 Aug 2020 13:55:44 +0200 |
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On 19/08/2020 13:05, Vincent Guittot wrote: > On Wed, 19 Aug 2020 at 12:46, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >> >> On 17/08/2020 14:05, benbjiang(蒋彪) wrote: >>> >>> >>>> On Aug 17, 2020, at 4:57 PM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>> >>>> On 14/08/2020 01:55, benbjiang(蒋彪) wrote: >>>>> Hi, >>>>> >>>>>> On Aug 13, 2020, at 2:39 AM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>>> >>>>>> On 12/08/2020 05:19, benbjiang(蒋彪) wrote: >>>>>>> Hi, >>>>>>> >>>>>>>> On Aug 11, 2020, at 11:54 PM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>>>>> >>>>>>>> On 11/08/2020 02:41, benbjiang(蒋彪) wrote: >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>>> On Aug 10, 2020, at 9:24 PM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>>>>>>> >>>>>>>>>> On 06/08/2020 17:52, benbjiang(蒋彪) wrote: >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>>> On Aug 6, 2020, at 9:29 PM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>> On 03/08/2020 13:26, benbjiang(蒋彪) wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> On Aug 3, 2020, at 4:16 PM, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>> On 01/08/2020 04:32, Jiang Biao wrote: >>>>>>>>>>>>>>> From: Jiang Biao <benbjiang@tencent.com> >> >> [...] >> >>>> Are you sure about this? >>> Yes. :) >>>> >>>> The math is telling me for the: >>>> >>>> idle task: (3 / (1024 + 1024 + 3))^(-1) * 4ms = 2735ms >>>> >>>> normal task: (1024 / (1024 + 1024 + 3))^(-1) * 4ms = 8ms >>>> >>>> (4ms - 250 Hz) >>> My tick is 1ms - 1000HZ, which seems reasonable for 600ms? :) >> >> OK, I see. >> >> But here the different sched slices (check_preempt_tick()-> >> sched_slice()) between normal tasks and the idle task play a role to. >> >> Normal tasks get ~3ms whereas the idle task gets <0.01ms. > > In fact that depends on the number of CPUs on the system > :sysctl_sched_latency = 6ms * (1 + ilog(ncpus)) . On a 8 cores system, > normal task will run around 12ms in one shoot and the idle task still > one tick period
True. This is on a single CPU.
> Also, you can increase even more the period between 2 runs of idle > task by using cgroups and min shares value : 2
Ah yes, maybe this is what Jiang wants to do then? If his runtime does not have other requirements preventing this.
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