On 09/21/2016 11:20 AM, Michal Hocko wrote:

I would even question the per page block offlining itself. Why would
anybody want to offline few blocks rather than the whole node? What is
the usecase here?

The original reason was so that you could remove a DIMM or a riser card
full of DIMMs, which are certainly a subset of a node.

With virtual machines, perhaps you only want to make a small adjustment
to the memory that a VM has.  Or, perhaps the VM only _has_ one node.
Granted, ballooning takes care of a lot of these cases, but memmap[]
starts to get annoying at some point if you balloon too much memory away.

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