linux-kernel - Re: [PATCH] x86: numa: mm: kill double initialization for NODE

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Date:	Wed, 03 Apr 2013 09:54:33 +0800
From:	Lin Feng <linfeng@...fujitsu.com>
To:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
CC:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, yinghai@...nel.org,
	wency@...fujitsu.com, tangchen@...fujitsu.com
Subject: Re: [PATCH] x86: numa: mm: kill double initialization for NODE_DATA

Hi Wanpeng,

On 04/02/2013 06:57 PM, Wanpeng Li wrote:
>> >PS. For clarifying calling chains are showed as follows:
>> >setup_arch()
>> >  ...
>> >  initmem_init()
>> >    x86_numa_init()
>> >      numa_init()
>> >        numa_register_memblks()
>> >          setup_node_data()
>> >            NODE_DATA(nid)->node_id = nid;
>> >            NODE_DATA(nid)->node_start_pfn = start >> PAGE_SHIFT;
>> >            NODE_DATA(nid)->node_spanned_pages = (end - start) >> PAGE_SHIFT;
>> >  ...
>> >  x86_init.paging.pagetable_init()
>> >  paging_init()
>> >    ...
>> >    sparse_init()
>> >      sparse_early_usemaps_alloc_node()
>> >        sparse_early_usemaps_alloc_pgdat_section()
>> >          ___alloc_bootmem_node_nopanic()
>> >            __alloc_memory_core_early(pgdat->node_id,...)
>> >    ...
>> >    zone_sizes_init()
>> >      free_area_init_nodes()
>> >        free_area_init_node()
>> >          pgdat->node_id = nid;
>> >          pgdat->node_start_pfn = node_start_pfn;
>> >          calculate_node_totalpages();
>> >            pgdat->node_spanned_pages = totalpages;
>> >
> You miss the nodes which could become online at some point, but not
> online currently. 

Sorry, I'm not quite understanding what you said.

I keep node_set_online(nid) there. In boot phase if a node is online now it wil be 
reinitialized later by zone_sizes_init() else if a node is hotpluged after system is
up it will also be initialized by hotadd_new_pgdat() which falls into calling 
free_area_init_node().

Besides this I'm not sure there are any other dependency besides what you worry about,
while I tested this on a x86_64 numa system with hot-add nodes and the meminfo statics
looks right before and after hot-add memory.

thanks for your patient,
linfeng
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