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Date: Mon, 08 Oct 2012 13:26:16 +0800
From: Wen Congyang <wency@cn.fujitsu.com>
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To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 0/10] memory-hotplug: hot-remove physical memory
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At 10/06/2012 03:06 AM, KOSAKI Motohiro Wrote:
>> Known problems:
>> 1. memory can't be offlined when CONFIG_MEMCG is selected.
>>    For example: there is a memory device on node 1. The address range
>>    is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10,
>>    and memory11 under the directory /sys/devices/system/memory/.
>>    If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup
>>    when we online pages. When we online memory8, the memory stored page cgroup
>>    is not provided by this memory device. But when we online memory9, the memory
>>    stored page cgroup may be provided by memory8. So we can't offline memory8
>>    now. We should offline the memory in the reversed order.
>>    When the memory device is hotremoved, we will auto offline memory provided
>>    by this memory device. But we don't know which memory is onlined first, so
>>    offlining memory may fail. In such case, you should offline the memory by
>>    hand before hotremoving the memory device.
> 
> Just iterate twice. 1st iterate: offline every non primary memory
> block. 2nd iterate:
> offline primary (i.e. first added) memory block. It may work.
> 

OK, I will try it.

Thanks
Wen Congyang