Subject: Re: [PATCH RFC] mm/memory_hotplug: Introduce memory block types

From: Michal Hocko <[email-masked]>
Date: Thu, 4 Oct 2018 08:28:11 +0200

On Wed 03-10-18 19:00:29, David Hildenbrand wrote:
[...]
> Let me rephrase: You state that user space has to make the decision and
> that user should be able to set/reconfigure rules. That is perfectly fine.
> 
> But then we should give user space access to sufficient information to
> make a decision. This might be the type of memory as we learned (what
> some part of this patch proposes), but maybe later more, e.g. to which
> physical device memory belongs (e.g. to hotplug it all movable or all
> normal) ...

I am pretty sure that user knows he/she wants to use ballooning in
HyperV or Xen, or that the memory hotplug should be used as a "RAS"
feature to allow add and remove DIMMs for reliability. Why shouldn't we
have a package to deploy an appropriate set of udev rules for each of
those usecases? I am pretty sure you need some other plumbing to enable
them anyway (e.g. RAS would require to have movable_node kernel
parameters, ballooning a kernel module etc.).

Really, one udev script to rule them all will simply never work.
-- 
Michal Hocko
SUSE Labs