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SubjectRe: [PATCH v2 2/6] sched/rt: Optimize select_task_rq_rt() for non-RT curr task
Date
> 
> When selecting the cpu for a waking RT task, if curr is a non-RT
> task which is bound only on this cpu, then we can give it a chance
> to select a different cpu(definitely an idle cpu if existing) for
> the RT task to avoid curr starving.
>
> Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
> ---
> kernel/sched/rt.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index da6922e..dc1f7f0 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1340,6 +1340,11 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
> * runqueue. Otherwise simply start this RT task
> * on its current runqueue.
> *
> + * If the current task on @p's runqueue is a non-RT task,
> + * and this task is bound on current runqueue, then try to
> + * see if we can wake this RT task up on a different runqueue,
> + * we will definitely find an idle cpu if there is any.
> + *
> * We want to avoid overloading runqueues. If the woken
> * task is a higher priority, then it will stay on this CPU
> * and the lower prio task should be moved to another CPU.
> @@ -1356,9 +1361,8 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
> * This test is optimistic, if we get it wrong the load-balancer
> * will have to sort it out.
> */
> - if (curr && unlikely(rt_task(curr)) &&
> - (curr->nr_cpus_allowed < 2 ||
> - curr->prio <= p->prio)) {
> + if (curr && unlikely(curr->nr_cpus_allowed < 2 ||
> + curr->prio <= p->prio)) {

Nack, it is no meaning to compare apple against orange.

Hillf
> int target = find_lowest_rq(p);
>
> if (target != -1)
> --
> 1.7.9.5



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