Messages in this thread | | | Subject | Re: [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator | From | Dietmar Eggemann <> | Date | Mon, 6 Aug 2018 15:20:27 +0200 |
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On 08/06/2018 02:37 PM, Vincent Guittot wrote: > On Mon, 6 Aug 2018 at 14:29, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >> >> On 08/06/2018 12:33 PM, Vincent Guittot wrote: >>> On Mon, 6 Aug 2018 at 12:08, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>> >>>> On 08/06/2018 10:40 AM, Vincent Guittot wrote: >>>>> On Fri, 3 Aug 2018 at 17:55, Quentin Perret <quentin.perret@arm.com> wrote: >>>>>> >>>>>> On Friday 03 Aug 2018 at 15:49:24 (+0200), Vincent Guittot wrote: >>>>>>> On Fri, 3 Aug 2018 at 10:18, Quentin Perret <quentin.perret@arm.com> wrote: >>>>>>>> >>>>>>>> On Friday 03 Aug 2018 at 09:48:47 (+0200), Vincent Guittot wrote: >>>>>>>>> On Thu, 2 Aug 2018 at 18:59, Quentin Perret <quentin.perret@arm.com> wrote: >>>> >>>> [...] >>>> >>>>>> I think we're discussing two different things right now: >>>>>> 1. Should forkees go in find_energy_efficient_cpu() ? >>>>>> 2. Should forkees have 0 of initial util_avg when EAS is enabled ? >>>>> >>>>> It's the same topic: How EAS should consider a newly created task ? >>>>> >>>>> For now, we let the "performance" mode selects a CPU. This CPU will >>>>> most probably be worst CPU from a EAS pov because it's the idlest CPU >>>>> in the idlest group which is the opposite of what EAS tries to do >>>>> >>>>> The current behavior is : >>>>> For every new task, the cpu selection is done assuming it's a heavy >>>>> task with the max possible load_avg, and it looks for the idlest cpu. >>>>> This means that if the system is lightly loaded, scheduler will select >>>>> most probably a idle big core. >>>> >>>> AFAICS, task load doesn't seem to be used for find_idlest_cpu() ( >>>> find_idlest_group() and find_idlest_group_cpu()). So the forkee >>>> (SD_BALANCE_FORK) is placed independently of his task load. >>> >>> hmm ... so what is used if load or runnable load are not used ? >>> find_idlest_group() uses load and runnable load but skip spare >>> capacity in case of fork >> >> Yes, runnable load and load are used, but from the cpus, not from the task. > > yes that's right, I have skipped the "task" word when reading. > So scheduler looks for the idlest CPU taking into account only CPU > loads. Then the task load starts to highest value until it get a > chance to reduce and stabilize to its final value
This could potentially allow us to find a better init value for sa->[runnable]_load_avg. At least we could use the information of the initial task rq.
> >> >> [...]
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