linux-kernel - Re: [PATCH 04/19] sched/numa: Set preferred_node based on best

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Date:   Mon, 4 Jun 2018 14:23:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 04/19] sched/numa: Set preferred_node based on best_cpu

On Mon, Jun 04, 2018 at 03:30:13PM +0530, Srikar Dronamraju wrote:
> @@ -1785,15 +1786,13 @@ static int task_numa_migrate(struct task_struct *p)
>  	 * trying for a better one later. Do not set the preferred node here.
>  	 */
>  	if (p->numa_group) {
> -		struct numa_group *ng = p->numa_group;
> -
>  		if (env.best_cpu == -1)
>  			nid = env.src_nid;
>  		else
> -			nid = env.dst_nid;
> +			nid = cpu_to_node(env.best_cpu);

OK, the above matches the description, but I'm puzzled by the remainder:

>  
> -		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
> -			sched_setnuma(p, env.dst_nid);
> +		if (nid != p->numa_preferred_nid)
> +			sched_setnuma(p, nid);
>  	}

That seems to entirely loose the active_node thing, or are you saying
best_cpu already includes that? (Changelog could use a little help there
I suppose)