[Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc

[Reza Arbab]

On Fri, May 26, 2017 at 01:46:58PM +1000, Michael Ellerman wrote:
>Reza Arbab <arbab at linux.vnet.ibm.com> writes:
>
>> On Thu, May 25, 2017 at 04:19:53PM +1000, Michael Ellerman wrote:
>>>The commit message for 3af229f2071f says:
>>>
>>>    In practice, we never see a system with 256 NUMA nodes, and in fact, we
>>>    do not support node hotplug on power in the first place, so the nodes
>>>    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>    that are online when we come up are the nodes that will be present for
>>>    the lifetime of this kernel.
>>>
>>>Is that no longer true?
>>
>> I don't know what the reasoning behind that statement was at the time,
>> but as far as I can tell, the only thing missing for node hotplug now is
>> Balbir's patchset [1]. He fixes the resource issue which motivated
>> 3af229f2071f and reverts it.
>>
>> With that set, I can instantiate a new numa node just by doing
>> add_memory(nid, ...) where nid doesn't currently exist.
>
>But does that actually happen on any real system?

I don't know if anything currently tries to do this. My interest in 
having this working is so that in the future, our coherent gpu memory 
could be added as a distinct node by the device driver.

-- 
Reza Arbab