Re: [RFC PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes

[Michal Hocko]

On Thu 01-06-17 16:11:55, Vlastimil Babka wrote:
> On 06/01/2017 02:20 PM, Michal Hocko wrote:
[...]
> > Strictly speaking the semantic is not identical with the boot time
> > initialization because find_zone_movable_pfns_for_nodes covers only the
> > hotplugable range as described by the BIOS/FW. From my experience this
> > is usually a full node though (except for Node0 which is special and
> > never goes away completely). If this turns out to be a problem in the
> > real life we can tweak the code to store hotplug flag into memblocks
> > but let's keep this simple now.
> 
> Simple should work, hopefully.
> - if memory is hotplugged, it's obviously hotplugable, so we don't have
> to rely on BIOS description.

Not sure I understand. We do not have any information about the hotplug
status at the time we do online.

> - there shouldn't be a reason to offline a non-removable (part of) node
> and online it back (which would move it from Normal to Movable after
> your patch?), right?

not really. If the memblock was inside a kernel zone it will stay there
with a new online operation because we check for that explicitly.
-- 
Michal Hocko
SUSE Labs