linux-kernel - Re: [PATCH 3/3] acpi, memory-hotplug: Support getting hotplug info from SRAT.

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Message-ID: <5105DD4B.9020901@cn.fujitsu.com>
Date:	Mon, 28 Jan 2013 10:07:07 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, jiang.liu@...wei.com,
	wujianguo@...wei.com, wency@...fujitsu.com, laijs@...fujitsu.com,
	linfeng@...fujitsu.com, yinghai@...nel.org,
	isimatu.yasuaki@...fujitsu.com, rob@...dley.net,
	kosaki.motohiro@...fujitsu.com, minchan.kim@...il.com,
	mgorman@...e.de, rientjes@...gle.com, guz.fnst@...fujitsu.com,
	rusty@...tcorp.com.au, lliubbo@...il.com, jaegeuk.hanse@...il.com,
	tony.luck@...el.com, glommer@...allels.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 3/3] acpi, memory-hotplug: Support getting hotplug info
 from SRAT.

On 01/26/2013 09:29 AM, H. Peter Anvin wrote:
> On 01/25/2013 05:12 PM, Andrew Morton wrote:
>> On Fri, 25 Jan 2013 17:42:09 +0800
>> Tang Chen<tangchen@...fujitsu.com>  wrote:
>>
>>> NOTE: Using this way will cause NUMA performance down because the whole node
>>>        will be set as ZONE_MOVABLE, and kernel cannot use memory on it.
>>>        If users don't want to lose NUMA performance, just don't use it.
>>
>> I agree with this, but it means that nobody will test any of your new code.
>>
>> To get improved testing coverage, can you think of any temporary
>> testing-only patch which will cause testers to exercise the
>> memory-hotplug changes?
>>
>
> There is another problem: if ALL the nodes in the system support
> hotpluggable memory, what happens?
>

Hi HPA,

I think I missed this case. If all the memory is hotpluggable, and user 
specified
movablemem_map=acpi, all the memory could be set as movable, and the 
kernel will
fail to start.

I will post a patch to fix it. How about always keep node0 unhotpluggable ?

Thanks. :)
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