linux-kernel - Re: [PATCHv2 3/7] sched/fair: Consider misfit tasks when load-balancing

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Message-ID: <20180411105329.GI4043@hirez.programming.kicks-ass.net>
Date:   Wed, 11 Apr 2018 12:53:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Morten Rasmussen <morten.rasmussen@....com>
Cc:     mingo@...hat.com, valentin.schneider@....com,
        dietmar.eggemann@....com, vincent.guittot@...aro.org,
        gaku.inami.xh@...esas.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 3/7] sched/fair: Consider misfit tasks when
 load-balancing

On Thu, Mar 15, 2018 at 02:47:00PM +0000, Morten Rasmussen wrote:
> +	/*
> +	 * Don't try to pull misfit tasks we can't help.
> +	 */
> +	if (sgs->group_type == group_misfit_task &&
> +	    (!group_smaller_cpu_capacity(sg, sds->local) ||
> +	     !group_has_capacity(env, &sds->local_stat)))
> +		return false;
> +

I think that has the same 'problem' as last time, right? Since
group_smaller_cpu_capacity() is affected by RT/IRQ pressure.

We should have a comment stating this and preferably explaining why that
is ok.