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    Subject[RFCv5 PATCH 35/46] sched: Disable energy-unfriendly nohz kicks
    Date
    With energy-aware scheduling enabled nohz_kick_needed() generates many
    nohz idle-balance kicks which lead to nothing when multiple tasks get
    packed on a single cpu to save energy. This causes unnecessary wake-ups
    and hence wastes energy. Make these conditions depend on !energy_aware()
    for now until the energy-aware nohz story gets sorted out.

    cc: Ingo Molnar <mingo@redhat.com>
    cc: Peter Zijlstra <peterz@infradead.org>

    Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
    ---
    kernel/sched/fair.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 97eb83e..8e0cbd4 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -8424,12 +8424,13 @@ static inline bool nohz_kick_needed(struct rq *rq)
    if (time_before(now, nohz.next_balance))
    return false;

    - if (rq->nr_running >= 2)
    + if (rq->nr_running >= 2 &&
    + (!energy_aware() || cpu_overutilized(cpu)))
    return true;

    rcu_read_lock();
    sd = rcu_dereference(per_cpu(sd_busy, cpu));
    - if (sd) {
    + if (sd && !energy_aware()) {
    sgc = sd->groups->sgc;
    nr_busy = atomic_read(&sgc->nr_busy_cpus);

    --
    1.9.1


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