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Subject: Re: [PATCH] mm/alloc: fallback to first node if the wanted node
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To:     Pingfan Liu <kernelfans@gmail.com>, mhocko@kernel.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>
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Date:   Wed, 5 Dec 2018 10:40:14 +0100
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On 12/5/18 10:29 AM, Pingfan Liu wrote:
>> [    0.007418] Early memory node ranges
>> [    0.007419]   node   1: [mem 0x0000000000001000-0x000000000008efff]
>> [    0.007420]   node   1: [mem 0x0000000000090000-0x000000000009ffff]
>> [    0.007422]   node   1: [mem 0x0000000000100000-0x000000005c3d6fff]
>> [    0.007422]   node   1: [mem 0x00000000643df000-0x0000000068ff7fff]
>> [    0.007423]   node   1: [mem 0x000000006c528000-0x000000006fffffff]
>> [    0.007424]   node   1: [mem 0x0000000100000000-0x000000047fffffff]
>> [    0.007425]   node   5: [mem 0x0000000480000000-0x000000087effffff]
>>
>> There is clearly no node2. Where did the driver get the node2 from?

I don't understand these tables too much, but it seems the other nodes
exist without them:

[    0.007393] SRAT: PXM 2 -> APIC 0x20 -> Node 2

Maybe the nodes are hotplugable or something?

> Since using nr_cpus=4 , the node2 is not be instanced by x86 initalizing code.

Indeed, nr_cpus seems to restrict what nodes we allocate and populate
zonelists for.