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

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Message-ID: <20200508132130.GC1961@linux.vnet.ibm.com>
Date:   Fri, 8 May 2020 18:51:30 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     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>,
        Michael Ellerman <mpe@...erman.id.au>,
        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

* 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.

-- 
Thanks and Regards
Srikar Dronamraju