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Date:   Wed, 8 Aug 2018 10:00:49 +0200
From:   Oscar Salvador <osalvador@techadventures.net>
To:     David Hildenbrand <david@redhat.com>
Cc:     Jerome Glisse <jglisse@redhat.com>, akpm@linux-foundation.org,
        mhocko@suse.com, dan.j.williams@intel.com,
        pasha.tatashin@oracle.com, yasu.isimatu@gmail.com,
        logang@deltatee.com, dave.jiang@intel.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Oscar Salvador <osalvador@suse.de>
Subject: Re: [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and
 move it to offline_pages
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On Wed, Aug 08, 2018 at 09:51:50AM +0200, David Hildenbrand wrote:
> > I am pretty sure this is a dumb question, but why HMM/devm path
> > do not call online_pages/offline_pages?
> 
> I think mainly because onlining/offlining (wild guesses)
> 
> - calls memory notifiers
> - works with memory blocks
> 
> (and does some more things not applicable to ZONE_DEVICE memory)

Yes, you are right.
They call arch_add_memory while want_memblock being false and so they do not
get to call hotplug_memory_register which handles all the memory block stuff.

Thanks
-- 
Oscar Salvador
SUSE L3