linux-kernel - Re: [PATCH 0/6] mm: make movable onlining suck less

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Message-Id: <20170405154852.kdkwuudjv2jwvj5g@arbab-laptop>
Date:   Wed, 5 Apr 2017 10:48:52 -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 Wed, Apr 05, 2017 at 08:42:39AM +0200, Michal Hocko wrote:
>On Tue 04-04-17 16:43:39, Reza Arbab wrote:
>> 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.
>
>Could you add some printks to see why the sysfs creation failed please?

Ah, simple enough. It's this, right at the top of 
register_mem_sect_under_node():

	if (!node_online(nid))
		return 0;

That being the case, I really don't understand why your patches make any 
difference. Is node_set_online() being called later than before somehow?

-- 
Reza Arbab