Re: [PATCH 0/1] memory offline issues with hugepage size > memory block size

From: Dave Hansen
Date: Wed Sep 21 2016 - 14:27:57 EST

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.