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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Christopher Lameter <cl@linux.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Michal Hocko <mhocko@suse.com>,
        Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Gautham R Shenoy <ego@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 1/3] powerpc/numa: Set numa_node for all possible cpus
In-Reply-To: <20200508132130.GC1961@linux.vnet.ibm.com>
References: <20200501031128.19584-1-srikar@linux.vnet.ibm.com> <20200501031128.19584-2-srikar@linux.vnet.ibm.com> <alpine.DEB.2.21.2005022254170.28355@www.lameter.com> <20200508132130.GC1961@linux.vnet.ibm.com>
Date:   Mon, 11 May 2020 21:27:07 +1000
Message-ID: <87v9l2btkk.fsf@mpe.ellerman.id.au>
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Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> * Christopher Lameter <cl@linux.com> [2020-05-02 22:55:16]:
>
>> On Fri, 1 May 2020, Srikar Dronamraju wrote:
>> 
>> > -	for_each_present_cpu(cpu)
>> > -		numa_setup_cpu(cpu);
>> > +	for_each_possible_cpu(cpu) {
>> > +		/*
>> > +		 * Powerpc with CONFIG_NUMA always used to have a node 0,
>> > +		 * even if it was memoryless or cpuless. For all cpus that
>> > +		 * are possible but not present, cpu_to_node() would point
>> > +		 * to node 0. To remove a cpuless, memoryless dummy node,
>> > +		 * powerpc need to make sure all possible but not present
>> > +		 * cpu_to_node are set to a proper node.
>> > +		 */
>> > +		if (cpu_present(cpu))
>> > +			numa_setup_cpu(cpu);
>> > +		else
>> > +			set_cpu_numa_node(cpu, first_online_node);
>> > +	}
>> >  }
>> 
>> Can this be folded into numa_setup_cpu?
>> 
>> This looks more like numa_setup_cpu needs to change?
>
> We can fold this into numa_setup_cpu().
>
> However till now we were sure that numa_setup_cpu() would be called only for
> a present cpu. That assumption will change.
> + (non-consequential) an additional check everytime cpu is hotplugged in.
>
> If Michael Ellerman is okay with the change, I can fold it in.

Yes I agree it would be better in numa_setup_cpu().

cheers