linux-kernel - Re: [PATCH v2 11/13] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups

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Message-ID: <20160712125953.GP30909@twins.programming.kicks-ass.net>
Date:	Tue, 12 Jul 2016 14:59:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	mingo@...hat.com, dietmar.eggemann@....com, yuyang.du@...el.com,
	vincent.guittot@...aro.org, mgalbraith@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/13] sched/fair: Avoid pulling tasks from
 non-overloaded higher capacity groups

On Wed, Jun 22, 2016 at 06:03:22PM +0100, Morten Rasmussen wrote:
> @@ -6892,6 +6903,19 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>  	if (sgs->avg_load <= busiest->avg_load)
>  		return false;
>  
> +	if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
> +		goto asym_packing;

Does this rely on the 'funny' ASYM_CAP semantics?

> +
> +	/* Candidate sg has no more than one task per cpu and has

Tssk, borken comment style.

> +	 * higher per-cpu capacity. Migrating tasks to less capable
> +	 * cpus may harm throughput. Maximize throughput,
> +	 * power/energy consequences are not considered.
> +	 */
> +	if (sgs->sum_nr_running <= sgs->group_weight &&
> +	    group_smaller_cpu_capacity(sds->local, sg))
> +		return false;
> +
> +asym_packing:
>  	/* This is the busiest node in its class. */
>  	if (!(env->sd->flags & SD_ASYM_PACKING))
>  		return true;
> -- 
> 1.9.1
>