linux-kernel - Re: [RFC v8 PATCH 00/20] memory-hotplug: hot-remove physical memory

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Date:	Mon, 10 Sep 2012 10:01:44 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-ia64@...r.kernel.org, cmetcalf@...era.com,
	sparclinux@...r.kernel.org, rientjes@...gle.com, liuj97@...il.com,
	len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
	cl@...ux.com, minchan.kim@...il.com, kosaki.motohiro@...fujitsu.com
Subject: Re: [RFC v8 PATCH 00/20] memory-hotplug: hot-remove physical memory

At 09/10/2012 09:46 AM, Yasuaki Ishimatsu Wrote:
> Hi Wen,
> 
> 2012/09/01 5:49, Andrew Morton wrote:
>> On Tue, 28 Aug 2012 18:00:07 +0800
>> wency@...fujitsu.com wrote:
>>
>>> This patch series aims to support physical memory hot-remove.
>>
>> Have you had much review and testing feedback yet?
>>
>>> The patches can free/remove the following things:
>>>
>>>    - acpi_memory_info                          : [RFC PATCH 4/19]
>>>    - /sys/firmware/memmap/X/{end, start, type} : [RFC PATCH 8/19]
>>>    - iomem_resource                            : [RFC PATCH 9/19]
>>>    - mem_section and related sysfs files       : [RFC PATCH 10-11,
>>> 13-16/19]
>>>    - page table of removed memory              : [RFC PATCH 12/19]
>>>    - node and related sysfs files              : [RFC PATCH 18-19/19]
>>>
>>> If you find lack of function for physical memory hot-remove, please
>>> let me
>>> know.
>>
> 
>> I doubt if many people have hardware which permits physical memory
>> removal?  How would you suggest that people with regular hardware can
>> test these chagnes?
> 
> How do you test the patch? As Andrew says, for hot-removing memory,
> we need a particular hardware. I think so too. So many people may want
> to know how to test the patch.
> If we apply following patch to kvm guest, can we hot-remove memory on
> kvm guest?
> 
> http://lists.gnu.org/archive/html/qemu-devel/2012-07/msg01389.html

Yes, if we apply this patchset, we can test hot-remove memory on kvm guest.
But that patchset doesn't implement _PS3, so there is some restriction.

Thanks
Wen Congyang

> 
> Thanks,
> Yasuaki Ishimatsu
> 
>>
>>> Known problems:
>>> 1. memory can't be offlined when CONFIG_MEMCG is selected.
>>
>> That's quite a problem!  Do you have a description of why this is the
>> case, and a plan for fixing it?
>>
> 
> 
> 

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