linux-kernel - Re: [PATCH v3 1/3] powerpc/numa: Set numa

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Date:   Mon, 11 May 2020 21:27:07 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Christopher Lameter <cl@...ux.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.com>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Gautham R Shenoy <ego@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3 1/3] powerpc/numa: Set numa_node for all possible cpus

Srikar Dronamraju <srikar@...ux.vnet.ibm.com> writes:
> * Christopher Lameter <cl@...ux.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