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Date: Tue, 29 Nov 2016 15:08:10 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Michal Hocko <mhocko@kernel.org>
cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-kernel@vger.kernel.org, rt@linutronix.de,
        Andrew Morton <akpm@linux-foundation.org>,
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        Mel Gorman <mgorman@techsingularity.net>,
        Johannes Weiner <hannes@cmpxchg.org>, linux-mm@kvack.org
Subject: Re: [PATCH 08/22] mm/vmstat: Avoid on each online CPU loops
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References: <20161126231350.10321-1-bigeasy@linutronix.de> <20161126231350.10321-9-bigeasy@linutronix.de> <20161128092800.GC14835@dhcp22.suse.cz>
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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