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    SubjectRe: [patch] RCU for low latency [1/2]


    Dipankar Sarma wrote:

    >Provide a rq_has_rt_task() interface to detect runqueues with
    >real time priority tasks. Useful for RCU optimizations.
    >

    Can you make rq_has_rt_task the slow path? Adding things like this
    can actually be noticable on microbenchmarks (eg. pipe based ctx
    switching). Its probably cache artifacts that I see, but it wouldn't
    hurt to keep the scheduler as tight as possible.

    I think this should cover it.

    int rq_has_rt_task(int cpu)
    {
    runqueue_t *rq = cpu_rq(cpu);
    return (sched_find_first_bit(rq->active) < MAX_RT_PRIO);
    }

    Any good?



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