Re: [PATCH 1/2] mm/migrate: optimize hotplug-time demotion order updates

[Dave Hansen]

On 9/21/21 7:36 AM, Huang, Ying wrote:
>> This removes the need for the demotion code to track *any* state.  I've
>> attached a totally untested patch to do this.
> Yes.  This sounds good.  I will try to test this patch on my side.
> 
>>From another point of view, we still need to update demotion order upon
> CPU hotplug too, because whether a node has CPU may be changed there.
> And we need a solution for that too.

Just to recap...  The reason I sent this series is that there's a known,
detectable regression in a memory hotplug "benchmark".  This affects the
5.15 series.

While I agree that we should look into the impact on CPU hotplug, I
think we should probably focus on the *known* memory hotplug issue for 5.15.