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

Yasuaki Ishimatsu
2012-10-02T10:00:42Z

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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