Messages in this thread | | | From | Vincent Guittot <> | Date | Fri, 10 Aug 2018 11:30:18 +0200 | Subject | Re: [PATCHv4 12/12] sched/core: Disable SD_PREFER_SIBLING on asymmetric cpu capacity domains |
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On Mon, 6 Aug 2018 at 12:53, Valentin Schneider <valentin.schneider@arm.com> wrote: > > Hi, > > On 06/08/18 11:20, Vincent Guittot wrote: > > Hi Valentin, > > > > On Tue, 31 Jul 2018 at 14:33, Valentin Schneider > > <valentin.schneider@arm.com> wrote: > >> > >> Hi, > >> > >> On 31/07/18 13:17, Vincent Guittot wrote: > >> [...] > >>>> > >>>> This can easily happen with SD_PREFER_SIBLING enabled too so I wouldn't > >>>> say that this patch breaks anything that isn't broken already. In fact > >>>> we this happening with and without this patch applied. > >>> > >>> At least for the use case above, this doesn't happen when > >>> SD_PREFER_SIBLING is set > >>> > >> > >> On my HiKey960 I can see coscheduling on a big CPU while a LITTLE is free > >> with **and** without SD_PREFER_SIBLING. Having it set only means that in > >> some cases the imbalance will be re-classified as group_overloaded instead > >> of group_misfit_task, so we'll skip the misfit logic when we shouldn't (this > >> happens on Juno for instance). > > > > Can you give more details about your test case ? > > > > I've been running the same test case as presented in the cover letter on > my HiKey960 but with sched_switch tracing and with no tasksets. I've just > re-run the testcase with tasksets and I get similar results (i.e. a big > with coscheduling while a LITTLE is free) with or without the flag. > > >> > >> It does nothing for the "1 task per CPU" problem that Morten described above. > >> When you have this little amount of tasks, load isn't very relevant, but it > >> skews the load-balancer into thinking the LITTLE CPUs are more busy than > >> the bigs even though there's an idle one in the lot.
ok. I meant that without misfit patch, SD_PREFER_SIBLING ensures 1 task per CPU and no co scheduling. But co scheduling appears with misfit task patchset
Vincent > >> > >>>> > >>>> Morten
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