linux-kernel - Re: [PATCH v3 4/6] sched/fair: Carve out logic to mark a group for asymmetric packing

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Message-ID: <51599adc-d7e6-9d29-9c17-a49e0c2e315e@arm.com>
Date:   Mon, 17 May 2021 16:21:36 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, 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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH v3 4/6] sched/fair: Carve out logic to mark a group for
 asymmetric packing

On 13/05/2021 17:49, Ricardo Neri wrote:

[...]

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c8c04e9d0d3b..c8b66a5d593e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8447,6 +8447,20 @@ group_type group_classify(unsigned int imbalance_pct,
>  	return group_has_spare;
>  }
>  
> +static inline bool
> +sched_asym(struct lb_env *env, struct sd_lb_stats *sds,  struct sg_lb_stats *sgs,
> +	   struct sched_group *group)
> +{
> +	/*
> +	 * Because sd->groups starts with the local group, anything that isn't
> +	 * the local group will have access to the local state.
> +	 */
> +	if (group == sds->local)
> +		return false;

sched_asym() is called under if(!local_group ...) from
update_sg_lb_stats(). So why checking this here again?

[...]