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    SubjectRe: [PATCH] sched/fair: fix load_balance redo for null imbalance
    On Fri, Sep 07, 2018 at 09:51:04AM +0200, Vincent Guittot wrote:
    > It can happen that load_balance finds a busiest group and then a busiest rq
    > but the calculated imbalance is in fact null.

    Cute. Does that happen often?

    > If the calculated imbalance is null, it's useless to try to find a busiest
    > rq as no task will be migrated and we can return immediately.
    >
    > This situation can happen with heterogeneous system or smp system when RT
    > tasks are decreasing the capacity of some CPUs.

    Is it the result of one of those "force_balance" conditions in
    find_busiest_group() ? Should we not fix that to then return NULL
    instead?

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