linux-kernel - Re: [PATCH 0/4] acpi,memory-hotplug : implement framework for hot removing memory

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Date:	Sat, 06 Oct 2012 22:22:24 +0800
From:	Ni zhan Chen <nizhan.chen@...il.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC:	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, rientjes@...gle.com, liuj97@...il.com,
	len.brown@...el.com, cl@...ux.com, minchan.kim@...il.com,
	akpm@...ux-foundation.org, kosaki.motohiro@...fujitsu.com,
	wency@...fujitsu.com
Subject: Re: [PATCH 0/4] acpi,memory-hotplug : implement framework for hot
 removing memory

On 10/03/2012 05:52 PM, Yasuaki Ishimatsu wrote:
> We are trying to implement a physical memory hot removing function as
> following thread.
>
> https://lkml.org/lkml/2012/9/5/201
>
> But there is not enough review to merge into linux kernel.
>
> I think there are following blockades.
>   1. no physical memory hot removable system

Which kind of special machine support physical memory hot-remove now?

>   2. huge patch-set
>
> If you have a KVM system, we can get rid of 1st blockade. Because
> applying following patch, we can create memory hot removable system
> on KVM guest.
>
> http://lists.gnu.org/archive/html/qemu-devel/2012-07/msg01389.html
>
> 2nd blockade is own problem. So we try to divide huge patch into
> a small patch in each function as follows: 
>
>  - bug fix
>  - acpi framework
>  - kernel core
>
> We had already sent bug fix patches.
> https://lkml.org/lkml/2012/9/27/39
> https://lkml.org/lkml/2012/10/2/83
>
> The patch-set implements a framework for hot removing memory.
>
> The memory device can be removed by 2 ways:
> 1. send eject request by SCI
> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
>
> In the 1st case, acpi_memory_disable_device() will be called.
> In the 2nd case, acpi_memory_device_remove() will be called.
> acpi_memory_device_remove() will also be called when we unbind the
> memory device from the driver acpi_memhotplug.
>
> acpi_memory_disable_device() has already implemented a code which
> offlines memory and releases acpi_memory_info struct . But
> acpi_memory_device_remove() has not implemented it yet.
>
> So the patch prepares the framework for hot removing memory and
> adds the framework intoacpi_memory_device_remove(). And it prepares
> remove_memory(). But the function does nothing because we cannot
> support memory hot remove.
>
> --
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