linux-kernel - Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory

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Message-ID: <20190401115306.GF28293@dhcp22.suse.cz>
Date:   Mon, 1 Apr 2019 13:53:06 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, Jonathan.Cameron@...wei.com,
        anshuman.khandual@....com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded
 memory

On Mon 01-04-19 09:59:36, Oscar Salvador wrote:
> On Fri, Mar 29, 2019 at 02:42:43PM +0100, Michal Hocko wrote:
> > Having a larger contiguous area is definitely nice to have but you also
> > have to consider the other side of the thing. If we have a movable
> > memblock with unmovable memory then we are breaking the movable
> > property. So there should be some flexibility for caller to tell whether
> > to allocate on per device or per memblock. Or we need something to move
> > memmaps during the hotremove.
> 
> By movable memblock you mean a memblock whose pages can be migrated over when
> this memblock is offlined, right?

I am mostly thinking about movable_node kernel parameter which makes
newly hotpluged memory go into ZONE_MOVABLE and people do use that to
make sure such a memory can be later hotremoved.

-- 
Michal Hocko
SUSE Labs