linux-kernel - Re: [RFC v1 00/19] Modify zonelist to nodelist v1

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Date:   Tue, 26 Nov 2019 14:04:06 -0500
From:   Qian Cai <cai@....pw>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Pengfei Li <fly@...nel.page>,
        "lixinhai.lxh@...il.com" <lixinhai.lxh@...il.com>,
        akpm <akpm@...ux-foundation.org>,
        mgorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>, cl <cl@...ux.com>,
        "iamjoonsoo.kim" <iamjoonsoo.kim@....com>, guro <guro@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC v1 00/19] Modify zonelist to nodelist v1



> On Nov 26, 2019, at 10:41 AM, Michal Hocko <mhocko@...nel.org> wrote:
> 
> On Tue 26-11-19 10:30:56, Qian Cai wrote:
>> 
>> 
>>> On Nov 25, 2019, at 3:39 AM, Michal Hocko <mhocko@...nel.org> wrote:
>>> 
>>> People do care about ZONE_MOVABLE and if there is a non-movable memory
>>> sitting there then it is a bug. Please report that.
>> 
>> It is trivial to test yourself if you ever care. Just pass kernelcore=
>> to as many NUMA machines you could find, an then test if ever possible
>> to offline those memory.
> 
> I definitely do care if you can provide more details (ideally in a
> separate email thread). I am using movable memory for memory hotplug
> usecases and so far I do not remember any kernel/non-movable allocations
> would make it in - modulo bugs when somebody might use __GFP_MOVABLE
> when it is not appropriate.
> 

I don’t think it is anything to do with __GFP_MOVABLE. It is about booting a kernel
with either passing kernelcore= or movablecore=. Then, those ZONE_MOVABLE will
have non-movable pages which looks like those from vmemmap_populate(). How
do you create ZONE_MOVALBLE in this first place?