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

[Michal Hocko]

On Thu 01-06-17 10:19:36, Reza Arbab wrote:
> On Thu, Jun 01, 2017 at 04:22:28PM +0200, Michal Hocko wrote:
> >On Thu 01-06-17 16:11:55, Vlastimil Babka wrote:
> >>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.
> 
> The x86 SRAT (or the dt, on other platforms) can describe memory as
> hotpluggable. See memblock_mark_hotplug(). That's only for memory present at
> boot, though.

Yes but lose that information after the memblock is gone and numa fully
initialized. Or can we reconstruct that somehow?

> He's saying that since the memory was added after boot, it is by definition
> hotpluggable. There's no need to check for that marking/description.

Yes, but we do not know whether we are onlining memblocks from a boot
time numa node or a fresh one which has been hotadded.
-- 
Michal Hocko
SUSE Labs