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

[Michael Bringmann]

I am running into this problem on PowerPC systems where Balbir's patch set
was targeted.  So, yes, I do need to be able to add/enable a new numa node
during system execution in cases where more resources (memory, virtual
processors) are added to the system dynamically.

On 05/25/2017 10:46 PM, Michael Ellerman wrote:
> Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx> 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?
> 
> cheers
> 
> 

-- 
Michael W. Bringmann
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