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    SubjectRe: [PATCH v3 09/12] Revert "sched: Put rq's sched_avg under CONFIG_FAIR_GROUP_SCHED"
    On 11 July 2014 18:13, Morten Rasmussen <morten.rasmussen@arm.com> wrote:

    [snip]

    >
    > In this example using rq->avg leads to imbalance whereas unweighted load
    > would not. Correct me if I missed anything.

    You just miss to take into account how the imbalance is computed

    >
    > Coming back to the previous example. I'm not convinced that inflation of
    > the unweighted load sum when tasks overlap in time is a bad thing. I
    > have mentioned this before. The average cpu utilization over the 40ms
    > period is 50%. However the true compute capacity demand is 200% for the
    > first 15ms of the period, 100% for the next 5ms and 0% for the remaining
    > 25ms. The cpu is actually overloaded for 15ms every 40ms. This fact is
    > factored into the unweighted load whereas rq->avg would give you the
    > same utilization no matter if the tasks are overlapped or not. Hence
    > unweighted load would give us an indication that the mix of tasks isn't
    > optimal even if the cpu has spare cycles.
    >
    > If you don't care about overlap and latency, the unweighted sum of task
    > running time (that Peter has proposed a number of times) is better
    > metric, IMHO. As long the cpu isn't fully utilized.
    >
    > Morten


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