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Subject: Re: [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus
To:     Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Joonsoo Kim <js1304@gmail.com>
Cc:     Sachin Sant <sachinp@linux.vnet.ibm.com>,
        Michal Hocko <mhocko@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Mel Gorman <mgorman@suse.de>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Andrew Morton <akpm@linux-foundation.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Christopher Lameter <cl@linux.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Michael Ellerman <mpe@ellerman.id.au>
References: <20200311110237.5731-2-srikar@linux.vnet.ibm.com>
 <20200311115735.GM23944@dhcp22.suse.cz>
 <20200312052707.GA3277@linux.vnet.ibm.com>
 <C5560C71-483A-41FB-BDE9-526F1E0CFA36@linux.vnet.ibm.com>
 <5e5c736a-a88c-7c76-fc3d-7bc765e8dcba@suse.cz>
 <20200312131438.GB3277@linux.vnet.ibm.com>
 <61437352-8b54-38fa-4471-044a65c9d05a@suse.cz>
 <20200312161310.GC3277@linux.vnet.ibm.com>
 <e115048c-be38-c298-b8d1-d4b513e7d2fb@suse.cz>
 <CAAmzW4OFy51BhAT62tdVQD52NNMWm+UPgoGAX97omY7P+nJ+5w@mail.gmail.com>
 <20200313110440.GA25144@linux.vnet.ibm.com>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <06be5908-9af6-2892-0333-e9558b2cf474@suse.cz>
Date:   Fri, 13 Mar 2020 12:38:45 +0100
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On 3/13/20 12:04 PM, Srikar Dronamraju wrote:
>> I lost all the memory about it. :)
>> Anyway, how about this?
>> 
>> 1. make node_present_pages() safer
>> static inline node_present_pages(nid)
>> {
>> if (!node_online(nid)) return 0;
>> return (NODE_DATA(nid)->node_present_pages);
>> }
>> 
> 
> Yes this would help.

Looks good, yeah.

>> 2. make node_to_mem_node() safer for all cases
>> In ppc arch's mem_topology_setup(void)
>> for_each_present_cpu(cpu) {
>>  numa_setup_cpu(cpu);
>>  mem_node = node_to_mem_node(numa_mem_id());
>>  if (!node_present_pages(mem_node)) {
>>   _node_numa_mem_[numa_mem_id()] = first_online_node;
>>  }
>> }
>> 
> 
> But here as discussed above, we miss the case of possible but not present nodes.
> For such nodes, the above change may not update, resulting in they still
> having 0. And node 0 can be only possible but not present.

So is there other way to do the setup so that node_to_mem_node() returns an
online+present node when called for any possible node?