linux-kernel - Re: [PATCH 1/1] memhp: Add hot-added memory ranges to memblock before allocate node

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Date:	Tue, 25 Aug 2015 09:09:53 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Tang Chen <tangchen@...fujitsu.com>
CC:	<akpm@...ux-foundation.org>, <isimatu.yasuaki@...fujitsu.com>,
	<n-horiguchi@...jp.nec.com>, <vbabka@...e.cz>,
	<mgorman@...hsingularity.net>, <rientjes@...gle.com>,
	<kamezawa.hiroyu@...fujitsu.com>, <izumi.taku@...fujitsu.com>,
	<yasu.isimatu@...il.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] memhp: Add hot-added memory ranges to memblock before
 allocate node_data for a node.

On 2015/8/24 17:22, Xishi Qiu wrote:

> On 2015/8/24 1:06, Tang Chen wrote:
> 
>> The commit below adds hot-added memory range to memblock, after
>> creating pgdat for new node.
>>
>> commit f9126ab9241f66562debf69c2c9d8fee32ddcc53
>> Author: Xishi Qiu <qiuxishi@...wei.com>
>> Date:   Fri Aug 14 15:35:16 2015 -0700
>>
>>     memory-hotplug: fix wrong edge when hot add a new node
>>
>> But there is a problem:
>>
>> add_memory()
>> |--> hotadd_new_pgdat()
>>      |--> free_area_init_node()
>>           |--> get_pfn_range_for_nid()
>>                |--> find start_pfn and end_pfn in memblock
>> |--> ......
>> |--> memblock_add_node(start, size, nid)    --------    Here, just too late.
>>
>> get_pfn_range_for_nid() will find that start_pfn and end_pfn are both 0.
>> As a result, when adding memory, dmesg will give the following wrong message.
>>

Hi Tang,

Another question, if we add cpu first, there will be print error too.

cpu_up()
	try_online_node()
		hotadd_new_pgdat()

So how about just skip the print if the size is empty or just print 
"node xx is empty now, will update when online memory"? 

Thanks,
Xishi Qiu

>> [ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
>> [ 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]
>>



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