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Date:   Mon, 26 Oct 2020 09:28:14 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Joel Fernandes <joel@joelfernandes.org>
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        Tim Chen <tim.c.chen@intel.com>
Subject: Re: [PATCH v8 -tip 06/26] sched: Add core wide task selection and
 scheduling.
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On Fri, Oct 23, 2020 at 05:31:18PM -0400, Joel Fernandes wrote:
> BTW, as further optimization in the future, isn't it better for the
> schedule() loop on 1 HT to select for all HT *even if* need_sync == false to
> begin with?  i.e. no cookied tasks are runnable.
> 
> That way the pick loop in schedule() running on other HTs can directly pick
> what was pre-selected for it via:
>         if (rq->core->core_pick_seq == rq->core->core_task_seq &&
>             rq->core->core_pick_seq != rq->core_sched_seq &&
>             rq->core_pick)
> .. which I think is more efficient. Its just a thought and may not be worth doing.

I'm not sure that works. Imagine a sibling doing a wakeup (or sleep)
just after you done your core wide pick. Then it will have to repick and
you end up with having to do 2*nr_smt picks instead of 2 picks.