linux-kernel - Re: [PATCH v5 08/12] sched: move cfs task on a CPU with higher capacity

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Date:	Thu, 11 Sep 2014 12:07:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	preeti@...ux.vnet.ibm.com, linux@....linux.org.uk,
	linux-arm-kernel@...ts.infradead.org, riel@...hat.com,
	Morten.Rasmussen@....com, efault@....de, nicolas.pitre@...aro.org,
	linaro-kernel@...ts.linaro.org, daniel.lezcano@...aro.org,
	dietmar.eggemann@....com
Subject: Re: [PATCH v5 08/12] sched: move cfs task on a CPU with higher
 capacity

On Tue, Aug 26, 2014 at 01:06:51PM +0200, Vincent Guittot wrote:

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 18db43e..60ae1ce 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6049,6 +6049,14 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>  			return true;
>  	}
>  
> +	/*
> +	 * The group capacity is reduced probably because of activity from other
> +	 * sched class or interrupts which use part of the available capacity
> +	 */
> +	if ((sg->sgc->capacity_orig * 100) > (sgs->group_capacity *
> +				env->sd->imbalance_pct))
> +		return true;
> +
>  	return false;
>  }

This is unlikely to have worked as intended. You will never reach this,
except on PowerPC >= 7. All other machines will have bailed at the
!ASYM_PACKING check above this.
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