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SubjectRe: [PATCH v4 08/10] sched/fair: Steal work from an overloaded CPU when CPU goes idle
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Hi Steve,

On 06/12/2018 21:28, Steve Sistare wrote:
[...]
> @@ -6778,20 +6791,22 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
> update_misfit_status(NULL, rq);
>
> /*
> - * We must set idle_stamp _before_ calling idle_balance(), such that we
> - * measure the duration of idle_balance() as idle time.
> + * We must set idle_stamp _before_ calling try_steal() or
> + * idle_balance(), such that we measure the duration as idle time.
> */
> rq_idle_stamp_update(rq);
>

idle_balance() has a

/*
* Do not pull tasks towards !active CPUs...
*/
if (!cpu_active(this_cpu))
return 0;

check which we probably want for stealing too, so we could hoist it up here
to cover both idle_balance() and try_steal().

> new_tasks = idle_balance(rq, rf);
> + if (new_tasks == 0)
> + new_tasks = try_steal(rq, rf);
>
> if (new_tasks)
> rq_idle_stamp_clear(rq);
>
> /*
> - * Because idle_balance() releases (and re-acquires) rq->lock, it is
> - * possible for any higher priority task to appear. In that case we
> - * must re-start the pick_next_entity() loop.
> + * Because try_steal() and idle_balance() release (and re-acquire)
> + * rq->lock, it is possible for any higher priority task to appear.
> + * In that case we must re-start the pick_next_entity() loop.
> */
> if (new_tasks < 0)
> return RETRY_TASK;
[...]

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