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Message-Id: <20170404214339.6o4c4uhwudyhzbbo@arbab-laptop>
Date: Tue, 4 Apr 2017 16:43:39 -0500
From: Reza Arbab <arbab@...ux.vnet.ibm.com>
To: Michal Hocko <mhocko@...nel.org>
Cc: Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Andrea Arcangeli <aarcange@...hat.com>,
Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
Tang Chen <tangchen@...fujitsu.com>, qiuxishi@...wei.com,
Kani Toshimitsu <toshi.kani@....com>, slaoub@...il.com,
Joonsoo Kim <js1304@...il.com>,
Andi Kleen <ak@...ux.intel.com>,
Zhang Zhen <zhenzhang.zhang@...wei.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>,
Chris Metcalf <cmetcalf@...lanox.com>,
Dan Williams <dan.j.williams@...il.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Lai Jiangshan <laijs@...fujitsu.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 0/6] mm: make movable onlining suck less
On Tue, Apr 04, 2017 at 09:41:22PM +0200, Michal Hocko wrote:
>On Tue 04-04-17 13:30:13, Reza Arbab wrote:
>> I think I found another edge case. You
>> get an oops when removing all of a node's memory:
>>
>> __nr_to_section
>> __pfn_to_section
>> find_biggest_section_pfn
>> shrink_pgdat_span
>> __remove_zone
>> __remove_section
>> __remove_pages
>> arch_remove_memory
>> remove_memory
>
>Is this something new or an old issue? I believe the state after the
>online should be the same as before. So if you onlined the full node
>then there shouldn't be any difference. Let me have a look...
It's new. Without this patchset, I can repeatedly
add_memory()->online_movable->offline->remove_memory() all of a node's
memory.
>>From 1b08ecef3e8ebcef585fe8f2b23155be54cce335 Mon Sep 17 00:00:00 2001
>From: Michal Hocko <mhocko@...e.com>
>Date: Tue, 4 Apr 2017 21:09:00 +0200
>Subject: [PATCH] mm, hotplug: get rid of zone/node shrinking
>
...%<...
>---
> mm/memory_hotplug.c | 207 ----------------------------------------------------
> 1 file changed, 207 deletions(-)
Okay, getting further. With this I can again repeatedly add and remove,
but now I'm seeing a weird variation of that earlier issue:
1. add_memory(), online_movable
/sys/devices/system/node/nodeX/memoryY symlinks are created.
2. offline, remove_memory()
The node is offlined, since all memory has been removed, so all of
/sys/devices/system/node/nodeX is gone. This is normal.
3. add_memory(), online_movable
The node is onlined, so /sys/devices/system/node/nodeX is recreated,
and the memory is added, but just like earlier in this email thread,
the memoryY links are not there.
--
Reza Arbab
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