# Re: \[PATCH 0/10\] memory-hotplug: hot-remove physical memory

- From: Wen Congyang \<hidden\>
- Date: 2012-10-08 05:20:48 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2012/10/3935761
- Thread: https://ratatoskr.run/linux-mm/2012/10/3934510/t.md

```text
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
```