linux-kernel - Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages() and reset_node_managed_pages() in hotadd_new

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Date:	Wed, 26 Aug 2015 15:19:19 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	<izumi.taku@...fujitsu.com>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
Subject: Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()
 and reset_node_managed_pages() in hotadd_new_pgdat()


On 08/24/2015 07:24 PM, Xishi Qiu wrote:
> ......
>>>> [ 2007.584000] On node 5 totalpages: 0
>>>> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  Total pages: 32588823
>>>> [ 2007.594000] Policy zone: Normal
>>>> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>>>>
>>>>
>>>> And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo will break.
>>>>
>>> trigger call trace?
>> No. There is no error output. But if you see /sys/devices/system/node/nodeX/meminfo,
>> memory size will double because totalpages is calculated once here, and one more time
>> when onlining memory.
>>
> Hi Tang,
>
> Do you mean si_meminfo_node() -> val->totalram = managed_pages; will be added double?
> But my patch will keep it 0 in hotadd_new_pgdat(), so it will not be double, right?
>

Hi,

I mean this:

online_pages()
|--> zone->zone_pgdat->node_present_pages += onlined_pages;

It will be double.

Since meminfo data is retrieved from these kernel structures, /proc/meminfo
will be broken.


Actually speaking, reset it when hot-adding memory is not a good idea.
We should make the memory init code be suitable for both boot code and
memory hot-plug code.


Thanks.
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