linux-kernel - Re: [patch] x86: set hotpluggable nodes in nodes_possible

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Date:	Thu, 21 Jan 2010 15:31:59 +0800
From:	Haicheng Li <haicheng.li@...ux.intel.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Ingo Molnar <mingo@...hat.com>, Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [patch] x86: set hotpluggable nodes in nodes_possible_map

David Rientjes wrote:
> On Thu, 21 Jan 2010, Haicheng Li wrote:
> 
>> diff --git a/arch/x86/mm/srat_64.c b/arch/x86/mm/srat_64.c
>> index a271241..c5552ae 100644
>> --- a/arch/x86/mm/srat_64.c
>> +++ b/arch/x86/mm/srat_64.c
>> @@ -27,8 +27,18 @@ int acpi_numa __initdata;
>>
>>  static struct acpi_table_slit *acpi_slit;
>>
>> +/* nodes_parsed:
>> + *  - nodes with memory on
>> + * cpu_nodes_parsed:
>> + *  - nodes with cpu on
>> + * hp_nodes_parsed:
>> + *  - nodes with hotpluggable memory region
>> + *
>> + * We union these tree nodemasks to get node_possible_map.
>> + */
>>  static nodemask_t nodes_parsed __initdata;
>>  static nodemask_t cpu_nodes_parsed __initdata;
>> +static nodemask_t hp_nodes_parsed __initdata;
>>  static struct bootnode nodes[MAX_NUMNODES] __initdata;
>>  static struct bootnode nodes_add[MAX_NUMNODES];
>>
>> @@ -229,9 +239,11 @@ update_nodes_add(int node, unsigned long start, unsigned
>> long end)
>>  			printk(KERN_ERR "SRAT: Hotplug zone not continuous.
>> Partly ignored\n");
>>  	}
>>
>> -	if (changed)
>> +	if (changed) {
>> +		node_set(node, hp_nodes_parsed);
>>  		printk(KERN_INFO "SRAT: hot plug zone found %Lx - %Lx\n",
>>  				 nd->start, nd->end);
>> +	}
>>  }
>>
>>  /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
>> @@ -380,8 +392,10 @@ int __init acpi_scan_nodes(unsigned long start, unsigned
>> long end)
>>  		return -1;
>>  	}
>>
>> -	/* Account for nodes with cpus and no memory */
>> +	/* Account for nodes with memory and cpus */
>>  	nodes_or(node_possible_map, nodes_parsed, cpu_nodes_parsed);
>> +	/* Account for nodes with hotpluggable memory regions */
>> +	nodes_or(node_possible_map, node_possible_map, hp_nodes_parsed);
>>
>>  	/* Finally register nodes */
>>  	for_each_node_mask(i, node_possible_map)
>>
>>
> 
> Nack, we don't need to add yet another nodemask because you're having 
> trouble finding a new name for a cpu_nodes_parsed.  It would be perfectly 
Hey Dave, why do you think it's just a naming issue?

What I'm concerning is that your assumption of cpu_nodes_parsed use is wrong,
cpu_nodes_parsed is needed anyway since its semantics represent the node with cpu affinity rather 
than memless node, that's also why I originally doubted cpu_node_parsed cannot handle hotplug node.
we also need hp_nodes_parsed to represent the node with hotpluggable memory region, just like why we 
need nodes_parsed to repsent node with mem on.

The code could be straightforward and easy to undertand in this way.

> acceptable to rename nodes_parsed to mem_nodes and cpu_nodes_parsed to 
> no_mem_nodes, which are even shorter.  But we definitely don't need 
> another nodemask and I think we're convoluting the bug fix here way too 
> much.  Regardless of the future nomenclature, let's please merge my patch 
> to fix the outstanding kernel issue and then propose an alternative naming 
It's important to fix the outstanding kernel issue, that's also why I keep shooting down this issue. 
I wanna fix it thru a right way rather than just get it fixed.


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