Messages in this thread | | | Subject | Re: [PATCHv4 12/12] sched/core: Disable SD_PREFER_SIBLING on asymmetric cpu capacity domains | From | Valentin Schneider <> | Date | Mon, 6 Aug 2018 11:53:50 +0100 |
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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. >> >>>> >>>> Morten
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