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SubjectRe: [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator
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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.

[...]

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