Message-ID: <52091A10.4030501@zytor.com>
Date: Mon, 12 Aug 2013 10:23:28 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Tang Chen <imtangchen@gmail.com>
CC: Tejun Heo <tj@kernel.org>, Tang Chen <tangchen@cn.fujitsu.com>,
        robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl,
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Subject: Re: [PATCH part5 0/7] Arrange hotpluggable memory as ZONE_MOVABLE.
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On 08/12/2013 10:01 AM, Tang Chen wrote:
>>
>>> I'm just thinking of a more extreme case. For example, if a machine
>>> has only one node hotpluggable, and the kernel resides in that node.
>>> Then the system has no hotpluggable node.
>>
>> Yeah, sure, then there's no way that node can be hotpluggable and the
>> right thing to do is booting up the machine and informing the userland
>> that memory is not hotpluggable.
>>
>>> If we can prevent the kernel from using hotpluggable memory, in such
>>> a machine, users can still do memory hotplug.
>>>
>>> I wanted to do it as generic as possible. But yes, finding out the
>>> nodes the kernel resides in and make it unhotpluggable can work.
>>
>> Short of being able to remap memory under the kernel, I don't think
>> this can be very generic and as a compromise trying to keep as many
>> hotpluggable nodes as possible doesn't sound too bad.
> 
> I think making one of the node hotpluggable is better. But OK, it is
> no big deal. There won't be such machine in reality, I think. :)
> 

The user may very well have configured a system with mirrored memory for
the kernel node as that will be non-hotpluggable, but not for the
others.  One can wonder how much that actually buys in real life, but
still...

	-hpa


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