Comment # 6 on bug 1048190 from Michal Hocko

(In reply to Franck Bui from comment #4)
> (In reply to Michal Hocko from comment #2)
> > And btw. I am working on memory hotplug to actually drop this auto onlining
> > nonsense. It's been a wrong thing to since beginning. Let's not spread it
> > even more.
> 
> Any pointers to discussions related to this work ?

My attempt to drop auto_online can be found
http://lkml.kernel.org/r/20170227092817.23571-1-mhocko@kernel.org. There was
an opposition against doing that mainly based by an observation that the
some memory ballooning solutions based on the memory hotplug could lead to
memory depletion because the userspace might not react fast enough to online
memory while the physical hotadd would already consume memory resources for
the new memory.

Let's put aside what I think about memory hotplug based ballooning
solutions, this is fixable by either postponing memory resource allocation
to the online phase or by allocating those resources from the newly hotadded
memory range. This is something still on my todo list but a first (large)
step was redefining semantic of the memory online phase pulled in the 4.13
merge window http://lkml.kernel.org/r/20170515085827.16474-1-mhocko@kernel.org

Once we remove the memory resource allocation problem then there won't be
any real reason to have a broken policy in the kernel anymore and I will
suggest removing it from the kernel again.