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.