linux-kernel - Re: [PATCH v2 3/4] sched/fair: Consider SMT in ASYM

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Date:   Mon, 3 May 2021 12:02:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...nel.org>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.comi>, Mel Gorman <mgorman@...e.de>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Quentin Perret <qperret@...gle.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, Aubrey Li <aubrey.li@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH v2 3/4] sched/fair: Consider SMT in ASYM_PACKING load
 balance

On Tue, Apr 13, 2021 at 07:04:35PM -0700, Ricardo Neri wrote:
> @@ -8507,6 +8616,18 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>  	if (!sgs->sum_h_nr_running)
>  		return false;
>  
> +	/*
> +	 * @sg may have been tentatively classified as group_asym_packing.
> +	 * Now that we have sufficient information about @sds.local, reassess
> +	 * if asym packing migration can be done. Reclassify @sg. The only
> +	 * possible results are group_has_spare and group_fully_busy.
> +	 */
> +	if (sgs->group_type == group_asym_packing &&
> +	    !asym_can_pull_tasks(env->dst_cpu, sds, sgs, sg)) {
> +		sgs->group_asym_packing = 0;
> +		sgs->group_type = group_classify(env->sd->imbalance_pct, sg, sgs);
> +	}

So if this really is all about not having sds.local in
update_sd_lb_stats(), then that seems fixable. Let me haz a try.