linux-kernel - Re: [RFC PATCH] mm, memory_hotplug: support movable

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Message-Id: <20170601151935.m5jbfmugocc66qfq@arbab-laptop.localdomain>
Date:   Thu, 1 Jun 2017 10:19:36 -0500
From:   Reza Arbab <arbab@...ux.vnet.ibm.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mm, memory_hotplug: support movable_node for
 hotplugable nodes

On Thu, Jun 01, 2017 at 04:22:28PM +0200, Michal Hocko wrote:
>On Thu 01-06-17 16:11:55, Vlastimil Babka wrote:
>> Simple should work, hopefully.
>> - if memory is hotplugged, it's obviously hotplugable, so we don't have
>> to rely on BIOS description.
>
>Not sure I understand. We do not have any information about the hotplug
>status at the time we do online.

The x86 SRAT (or the dt, on other platforms) can describe memory as 
hotpluggable. See memblock_mark_hotplug(). That's only for memory 
present at boot, though.

He's saying that since the memory was added after boot, it is by 
definition hotpluggable. There's no need to check for that 
marking/description.

-- 
Reza Arbab