linux-kernel - Re: [PATCH 0/2] memory-hotplug : notification of memoty block's state

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Message-ID: <506ABB26.3020806@jp.fujitsu.com>
Date:	Tue, 2 Oct 2012 19:00:06 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Ni zhan Chen <nizhan.chen@...il.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 0/2] memory-hotplug : notification of memoty block's state

2012/10/02 18:42, Ni zhan Chen wrote:
> On 10/02/2012 04:25 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
>>    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
>>
>> And the patch fixes following bug.
>>
>> remove_memory() offlines memory. And it is called by following two cases:
>>
>> 1. echo offline >/sys/devices/system/memory/memoryXX/state
>> 2. hot remove a memory device
>>
>> In the 1st case, the memory block's state is changed and the notification
>> that memory block's state changed is sent to userland after calling
>> offline_memory(). So user can notice memory block is changed.,
> 
> Hi Yasuaki,
> 
> Thanks for splitting the patchset, it's more easier to review this time.
> One question:
> 
> How can notify userspace? you mean function node_memory_callback or
> ...., but

When calling memory_block_change_state(), it calls kobject_uevent().
This function notifies userspace of the online/offline notification.

Thanks,
Yasuaki Ishimatsu


> this function basically do nothing.
> 
>>
>> But in the 2nd case, the memory block's state is not changed and the
>> notification is not also sent to userspcae even if calling offline_memory().
>> So user cannot notice memory block is changed.
>>
>> We should also notify to userspace at 2nd case.
>>
>> --
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> 
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