Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory

Oscar Salvador
2019-04-03T09:40:57Z

On Wed, Apr 03, 2019 at 10:37:57AM +0200, Michal Hocko wrote:
> That being said it should be the caller of the hotplug code to tell
> the vmemmap allocation strategy. For starter, I would only pack vmemmaps
> for "regular" kernel zone memory. Movable zones should be more careful.
> We can always re-evaluate later when there is a strong demand for huge
> pages on movable zones but this is not the case now because those pages
> are not really movable in practice.

I agree that makes sense to let the caller specify if it wants to allocate
vmemmaps per memblock or per memory-range, so we are more flexible when it
comes to granularity in hot-add/hot-remove operations.

But the thing is that the zones are picked at onling stage, while
vmemmaps are created at hot-add stage, so I am not sure we can define
the strategy depending on the zone.

--
Oscar Salvador
SUSE L3