Re: [PATCH 1/3] powerpc/pseries: Simplify cpu readd to use drc_index

[Tyrel Datwyler <tyreld@linux.vnet.ibm.com>]

On 05/16/2019 12:17 PM, Nathan Lynch wrote:
> Tyrel Datwyler <tyreld@linux.ibm.com> writes:
>> The current dlpar_cpu_readd() takes in a cpu_id and uses that to look up
>> the cpus device_node so that we can get at the ibm,my-drc-index
>> property. The only user of cpu readd is an OF notifier call back. This
>> call back already has a reference to the device_node and therefore can
>> retrieve the drc_index from the device_node.
> 
> dlpar_cpu_readd is a hack to try to change the CPU-node relationship at
> runtime without destabilizing the system. It doesn't accomplish that and
> it should just be removed (and I'm working on that).
> 

I will politely disagree. We've done exactly this from userspace for years. My
experience still suggests that memory affinity is the problem area, and that the
work to push this all into the kernel originally was poorly tested.

-Tyrel