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    Subject[PATCH 7/8] Reprogram timers only when necessary
    Avoid unnecessary timer reprogramming when a group is at its full
    capacity and it is already enqueued. Such a group will not need
    further budget recharges until it astually consumes its budget, so
    do not rearm its timer immediately.
    ---
    kernel/sched_rt.c | 19 ++++++++++++++++++-
    1 files changed, 18 insertions(+), 1 deletions(-)

    diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
    index f43ce7b..a9db16b 100644
    --- a/kernel/sched_rt.c
    +++ b/kernel/sched_rt.c
    @@ -386,6 +386,19 @@ static int do_sched_rt_period_timer(struct rt_rq *rt_rq, int overrun)
    return idle;
    }

    +static inline int rt_rq_needs_recharge(struct rt_rq *rt_rq)
    +{
    + struct sched_rt_entity *rt_se = rt_rq->rt_se;
    +
    + if (rt_rq->rt_time)
    + return 1;
    +
    + if (!rt_se)
    + return 0;
    +
    + return !on_rt_rq(rt_rq->rt_se);
    +}
    +
    static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
    {
    struct rt_rq *rt_rq = container_of(timer, struct rt_rq,
    @@ -402,7 +415,8 @@ static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
    idle = do_sched_rt_period_timer(rt_rq, overrun);
    }

    - return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
    + return idle || !rt_rq_needs_recharge(rt_rq) ?
    + HRTIMER_NORESTART : HRTIMER_RESTART;
    }

    static void start_rt_period_timer(struct rt_rq *rt_rq)
    @@ -428,6 +442,9 @@ static void start_rt_period_timer(struct rt_rq *rt_rq)
    if (overrun)
    __do_sched_rt_period_timer(rt_rq, overrun);

    + if (!rt_rq_needs_recharge(rt_rq))
    + return;
    +
    soft = hrtimer_get_softexpires(&rt_rq->rt_period_timer);
    hard = hrtimer_get_expires(&rt_rq->rt_period_timer);
    range = ktime_to_ns(ktime_sub(hard, soft));
    --
    1.6.2.2


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