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    SubjectRe: [PATCH 1/4] sched/topology: Store root domain CPU capacity sum
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    On 14.04.20 14:45, Quentin Perret wrote:
    > On Wednesday 08 Apr 2020 at 19:03:57 (+0200), Vincent Guittot wrote:
    >> Or we can do the opposite and only use capacity_orig_of()/rq->cpu_capacity_orig.
    >>
    >> Is there a case where the max cpu capacity changes over time ? So I
    >> would prefer to use cpu_capacity_orig which is a field of scheduler
    >> instead of always calling an external arch specific function
    >
    > Note however that using arch_scale_cpu_capacity() would be more
    > efficient, especially on non-arm/arm64 systems where it is a
    > compile-time constant.

    or essentially all ARCHs not defining it.

    >
    > It's probably a matter of personal taste, but I find rq->cpu_capacity_orig
    > superfluous. It wastes space without actually giving you anything no?
    > Anybody remembers why it was introduced in the first place?

    v3.18 arm providing arch_scale_cpu_capacity()
    v4.1 introduction of rq->cpu_capacity_orig
    v4.10 arm64 providing arch_scale_cpu_capacity()
    ...

    So it's down to the question of 'minimizing the scheduler calls to an
    external arch function' vs 'efficiency'.

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