linux-kernel - Re: [PATCH 08/22] mm/vmstat: Avoid on each online CPU loops

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Message-ID: <alpine.DEB.2.20.1611291505340.4358@nanos>
Date:   Tue, 29 Nov 2016 15:08:10 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org, rt@...utronix.de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: Re: [PATCH 08/22] mm/vmstat: Avoid on each online CPU loops

On Mon, 28 Nov 2016, Michal Hocko wrote:
> On Sun 27-11-16 00:13:36, Sebastian Andrzej Siewior wrote:
> [...]
> >  static void __init init_cpu_node_state(void)
> >  {
> > -	int cpu;
> > +	int node;
> >  
> > -	for_each_online_cpu(cpu)
> > -		node_set_state(cpu_to_node(cpu), N_CPU);
> > +	for_each_online_node(node)
> > +		node_set_state(node, N_CPU);
> 
> Is this really correct? The point of the original code was to mark only
> those nodes which have at least one CPU. Or am I missing something?

You're right. An online node does not necessarily have an online CPU.

	for_each_online_node(node) {
		if (cpumask_weight(cpumask_of_node(node)) > 0)
			node_set_state(node, N_CPU);
	}

is probably more correct.

Thanks,

	tglx