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Date:   Thu, 28 Mar 2019 15:16:31 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Toshi Kani <toshi.kani@hpe.com>,
        Jeff Moyer <jmoyer@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        stable <stable@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 00/10] mm: Sub-section memory hotplug support
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On Thu 28-03-19 14:38:15, David Hildenbrand wrote:
> On 27.03.19 17:13, Michal Hocko wrote:
[...]
> > People are asking for a smaller memory hotplug granularity for other
> > usecases (e.g. memory ballooning into VMs) which are quite dubious to
> > be honest and not really worth all the code rework. If we are talking
> > about something that can be worked around elsewhere then it is preferred
> > because the code base is not in an excellent shape and putting more on
> > top is just going to cause more headaches.
> 
> At least for virtio-mem, it will be handled similar to xen-balloon and
> hyper-v balloon, where whole actions are added and some parts are kept
> "soft-offline". But there, one device "owns" the complete section, it
> does not overlap with other devices. One section only has one owner.

This is exactly what I meant by handing at a higher level.

-- 
Michal Hocko
SUSE Labs