Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle hugepage

[KOSAKI Motohiro]

>> numa_node_id() is really silly. This might lead to allocate from offlining node.
>
> Right, it should've been alloc_huge_page().
>
>> and, offline_pages() should mark hstate as isolated likes normal pages for prohibiting
>> new allocation at first.
>
> It seems that alloc_migrate_target() calls alloc_page() for normal pages
> and the destination pages can be in the same node with the source pages
> (new page allocation from the same memblock are prohibited.)

No. It can't. memory hotplug change buddy attribute to MIGRATE_ISOLTE at first.
then alloc_page() never allocate from source node. however huge page don't use
buddy. then we need another trick.


> So if we want to avoid new page allocation from the same node,
> this is the problem both for normal and huge pages.
>
> BTW, is it correct to think that all users of memory hotplug assume
> that they want to hotplug a whole node (not the part of it?)

Both are valid use case. admin can isolate a part of memory for isolating
broken memory range.

but I'm sure almost user want to remove whole node.
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