linux-kernel - Re: [V2 2/2] sched: update cfs_rq weight earlier in enqueue

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Date:	Mon, 1 Jul 2013 07:07:15 -0700
From:	Paul Turner <pjt@...gle.com>
To:	Lei Wen <leiwen@...vell.com>
Cc:	Alex Shi <alex.shi@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, Ingo Molnar <mingo@...hat.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [V2 2/2] sched: update cfs_rq weight earlier in enqueue_entity

Could you please restate the below?

On Mon, Jul 1, 2013 at 5:33 AM, Lei Wen <leiwen@...vell.com> wrote:
> Since we are going to calculate cfs_rq's average ratio by
> runnable_load_avg/load.weight

I don't understand what you mean by this.

>, if not increase the load.weight prior to
> enqueue_entity_load_avg, it may lead to one cfs_rq's avg ratio higher
> than 100%.
>

Or this.

> Adjust the sequence, so that all ratio is kept below 100%.
>
> Signed-off-by: Lei Wen <leiwen@...vell.com>
> ---
>  kernel/sched/fair.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 07bd74c..d1eee84 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1788,8 +1788,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
>          * Update run-time statistics of the 'current'.
>          */
>         update_curr(cfs_rq);
> -       enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
>         account_entity_enqueue(cfs_rq, se);
> +       enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);

account_entity_enqueue is independent of enqueue_entity_load_avg;
their order should not matter.

Further, should we restore the reverted amortization commit (improves
context switch times) enqueue_entity_load_avg needs to precede
account_entity_enqueue as it may update se->load.weight.

>         update_cfs_shares(cfs_rq);
>
>         if (flags & ENQUEUE_WAKEUP) {
> --
> 1.7.10.4
>
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