linux-kernel - Re: [PATCH 3/3] sched: terminate newidle balancing once at least one task has moved over

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Date:	Tue, 24 Jun 2008 10:50:11 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	mingo@...e.hu, rostedt@...dmis.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	linux-rt-users@...r.kernel.org, dbahi@...ell.com
Subject: Re: [PATCH 3/3] sched: terminate newidle balancing once at least one task has moved over

On Tuesday 24 June 2008 09:04, Gregory Haskins wrote:
> Inspired by Peter Zijlstra.

Is this really getting tested well? Because at least for SCHED_OTHER
tasks, the newidle balancer is still supposed to be relatively
conservative and not over balance too much. By the time you have
done all this calculation and reached here, it will be a loss to only
move one task if you could have moved two and halved your newidle
balance rate...

> Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
> ---
>
>  kernel/sched.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 3efbbc5..c8e8520 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -2775,6 +2775,10 @@ static int move_tasks(struct rq *this_rq, int
> this_cpu, struct rq *busiest, max_load_move - total_load_moved,
>  				sd, idle, all_pinned, &this_best_prio);
>  		class = class->next;
> +
> +		if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
> +			break;
> +
>  	} while (class && max_load_move > total_load_moved);
>
>  	return total_load_moved > 0;
>
> --
--
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